Longitudinal associations of diurnal rest-activity rhythms with fatigue, insomnia, and health-related quality of life in survivors of colorectal cancer up to 5 years post-treatment

BACKGROUND

There is a growing population of survivors of colorectal cancer (CRC). Fatigue and insomnia are common symptoms after CRC, negatively influencing health-related quality of life (HRQoL). Besides increasing physical activity and decreasing sedentary behavior, the timing and patterns of physical activity and rest over the 24-h day (i.e. diurnal rest-activity rhythms) could also play a role in alleviating these symptoms and improving HRQoL. We investigated longitudinal associations of the diurnal rest-activity rhythm (RAR) with fatigue, insomnia, and HRQoL in survivors of CRC.

METHODS

In a prospective cohort study among survivors of stage I-III CRC, 5 repeated measurements were performed from 6 weeks up to 5 years post-treatment. Parameters of RAR, including mesor, amplitude, acrophase, circadian quotient, dichotomy index, and 24-h autocorrelation coefficient, were assessed by a custom MATLAB program using data from tri-axial accelerometers worn on the upper thigh for 7 consecutive days. Fatigue, insomnia, and HRQoL were measured by validated questionnaires. Confounder-adjusted linear mixed models were applied to analyze longitudinal associations of RAR with fatigue, insomnia, and HRQoL from 6 weeks until 5 years post-treatment. Additionally, intra-individual and inter-individual associations over time were separated.

RESULTS

Data were available from 289 survivors of CRC. All RAR parameters except for 24-h autocorrelation increased from 6 weeks to 6 months post-treatment, after which they remained relatively stable. A higher mesor, amplitude, circadian quotient, dichotomy index, and 24-h autocorrelation were statistically significantly associated with less fatigue and better HRQoL over time. A higher amplitude and circadian quotient were associated with lower insomnia. Most of these associations appeared driven by both within-person changes over time and between-person differences in RAR parameters. No significant associations were observed for acrophase.

CONCLUSIONS

In the first five years after CRC treatment, adhering to a generally more active (mesor) and consistent (24-h autocorrelation) RAR, with a pronounced peak activity (amplitude) and a marked difference between daytime and nighttime activity (dichotomy index) was found to be associated with lower fatigue, lower insomnia, and a better HRQoL. Future intervention studies are needed to investigate if restoring RAR among survivors of CRC could help to alleviate symptoms of fatigue and insomnia while enhancing their HRQoL.

TRIAL REGISTRATION

EnCoRe study NL6904 ( https://www.onderzoekmetmensen.nl/ ).

Impact of polygenic score for BMI on weight loss effectiveness and genome-wide association analysis

BACKGROUND

While environmental factors play an important role in weight loss effectiveness, genetics may also influence its success. We examined whether a genome-wide polygenic score for BMI was associated with weight loss effectiveness and aimed to identify common genetic variants associated with weight loss.

METHODS

Participants in the ONTIME study (n = 1210) followed a uniform, multimodal behavioral weight-loss intervention. We first tested associations between a genome-wide polygenic score for higher BMI and weight loss effectiveness (total weight loss, rate of weight loss, and attrition). We then conducted a genome-wide association study (GWAS) for weight loss in the ONTIME study and performed the largest weight loss meta-analysis with earlier studies (n = 3056). Lastly, we ran exploratory GWAS in the ONTIME study for other weight loss outcomes and related factors.

RESULTS

We found that each standard deviation increment in the polygenic score was associated with a decrease in the rate of weight loss (Beta (95% CI) = -0.04 kg per week (-0.06, -0.01); P = 3.7 × 10-03) and with higher attrition after adjusting by treatment duration. No associations reached genome-wide significance in meta-analysis with previous GWAS studies for weight loss. However, associations in the ONTIME study showed effects consistent with published studies for rs545936 (MIR486/NKX6.3/ANK1), a previously noted weight loss locus. In the meta-analysis, each copy of the minor A allele was associated with 0.12 (0.03) kg/m2 higher BMI at week five of treatment (P = 3.9 × 10-06). In the ONTIME study, we also identified two genome-wide significant (P < 5×10-08) loci for the rate of weight loss near genes implicated in lipolysis, body weight, and metabolic regulation: rs146905606 near NFIP1/SPRY4/FGF1; and rs151313458 near LSAMP.

CONCLUSION

Our findings are expected to help in developing personalized weight loss approaches based on genetics.

CLINICAL TRIAL REGISTRATION

Obesity, Nutrigenetics, Timing, and Mediterranean (ONTIME; clinicaltrials.gov: NCT02829619) study.

Social jetlag and obesity: A systematic review and meta-analysis

Social jetlag, the weekly variation in sleep timing, is proposed to contribute to increased obesity risk, potentially because of the misalignment of behavioral cycles relative to the endogenous circadian timing system. This systematic review and meta-analysis aim to determine the association between social jetlag and adiposity-related measures using observational studies. We reviewed 477 references, of which 43 studies met inclusion criteria with a total sample size of 231,648. There was a positive association between social jetlag and body mass index (correlation coefficient [r]: 0.12; 95%CI, 0.07, 0.17; P < 0.001; I2  = 94.99%), fat mass (r: 0.10; 95%CI, 0.05, 0.15; P < 0.001; I2  = 0.00%), fat mass index (fat mass divided by height in meter squared, β: 0.14 kg/m2 ; 95%CI, 0.05, 0.23; P < 0.001; I2  = 56.50%), percent of body fat (r: 0.37; 95%CI, 0.33, 0.41; P < 0.001; I2  = 96.17%), waist circumference (r: 0.15; 95%CI, 0.06, 0.24; P = 0.001; I2  = 90.83%), and the risk of having overweight/obesity (odds ratio: 1.20; 95%CI, 1.02, 1.140; P = 0.039; I2  = 98.25%). Social jetlag is positively and consistently associated with multiple obesity-related anthropometric measures. Further studies are needed to test causality, underlying mechanisms, and whether obesity interventions based on increasing regularity of the sleep/wake cycle can aid in the battle against the obesity pandemic.

Light exposure during sleep is bidirectionally associated with irregular sleep timing: The multi-ethnic study of atherosclerosis (MESA)

Exposure to light at night (LAN) may influence sleep timing and regularity. Here, we test whether greater light exposure during sleep (LEDS) is bidirectionally associated with greater irregularity in sleep onset timing in a large cohort of older adults in cross-sectional and short-term longitudinal (days) analyses. Light exposure and activity patterns, measured via wrist-worn actigraphy (ActiWatch Spectrum), were analyzed in 1933 participants with 6+ valid days of data in the Multi-Ethnic Study of Atherosclerosis (MESA) Exam 5 Sleep Study. Summary measures of LEDS averaged across nights were evaluated in linear and logistic regression analyses to test the association with standard deviation (SD) in sleep onset timing (continuous variable) and irregular sleep onset timing (SD > 90 min, binary). Night-to-night associations between LEDS and absolute differences in nightly sleep onset timing were also evaluated with distributed lag non-linear models and mixed models. In between-individual linear and logistic models adjusted for demographic, health, and seasonal factors, every 5-lux unit increase in LEDS was associated with a 7.8-min increase in sleep onset SD (β = 0.13 h, 95%CI:0.09-0.17) and 32% greater odds (OR = 1.32, 95%CI:1.17-1.50) of irregular sleep onset. In within-individual night-to-night mixed model analyses, every 5-lux unit increase in LEDS the night prior was associated with a 2.2-min greater deviation of sleep onset the next night (β = 0.036 h, p < 0.05). Conversely, every 1-h increase in sleep deviation was associated with a 0.35-lux increase in future LEDS (β = 0.348 lux, p < 0.05). LEDS was associated with greater irregularity in sleep onset in between-individual analyses and subsequent deviation in sleep timing in within-individual analyses, supporting a role for LEDS in irregular sleep onset timing. Greater deviation in sleep onset was also associated with greater future LEDS, suggesting a bidirectional relationship. Maintaining a dark sleeping environment and preventing LEDS may promote sleep regularity and following a regular sleep schedule may limit LEDS.

The sleep-circadian interface: A window into mental disorders

Sleep, circadian rhythms, and mental health are reciprocally interlinked. Disruption to the quality, continuity, and timing of sleep can precipitate or exacerbate psychiatric symptoms in susceptible individuals, while treatments that target sleep-circadian disturbances can alleviate psychopathology. Conversely, psychiatric symptoms can reciprocally exacerbate poor sleep and disrupt clock-controlled processes. Despite progress in elucidating underlying mechanisms, a cohesive approach that integrates the dynamic interactions between psychiatric disorder with both sleep and circadian processes is lacking. This review synthesizes recent evidence for sleep-circadian dysfunction as a transdiagnostic contributor to a range of psychiatric disorders, with an emphasis on biological mechanisms. We highlight observations from adolescent and young adults, who are at greatest risk of developing mental disorders, and for whom early detection and intervention promise the greatest benefit. In particular, we aim to a) integrate sleep and circadian factors implicated in the pathophysiology and treatment of mood, anxiety, and psychosis spectrum disorders, with a transdiagnostic perspective; b) highlight the need to reframe existing knowledge and adopt an integrated approach which recognizes the interaction between sleep and circadian factors; and c) identify important gaps and opportunities for further research.

Endogenous circadian rhythms in mood and well-being

OBJECTIVES

We examined whether the endogenous circadian timing system modulates proxies of mood vulnerability and well-being.

METHODS

Nineteen healthy participants (mean age: 26.6 years [23.0-30.2], seven females, body-mass index: 22.8 kg/m2 [21.1-25]) completed a laboratory protocol with a 32-hour Constant Routine, a stringently controlled protocol designed to isolate assessment of endogenous circadian rhythms. We assessed hourly anxiety- and depression-like mood (i.e., those typically observed in depression and anxiety) and well-being (i.e., associated with mental fatigue and physical comfort).

RESULTS

Significant endogenous circadian rhythms were observed in anxiety-like and depression-like mood, as well as well-being (p values from the mixed-model analysis using false discovery rates < .001). Post-hoc comparisons revealed more anxiety-like and depression-like mood during the circadian phase 60°-75° (∼8-9 a.m.), and more mental fatigue and less physical comfort during the circadian phase 30°-60° (∼6-8 a.m.).

CONCLUSIONS

Our data indicate endogenous circadian rhythms in anxiety-like and depression-like mood and well-being in healthy young adults. Future studies will help establish circadian-based therapeutics for individuals experiencing mood and anxiety disorders.

Effects of Sleep Fragmentation and Estradiol Decline on Cortisol in a Human Experimental Model of Menopause

CONTEXT

Perturbations to the hypothalamic-pituitary-adrenal (HPA) axis have been hypothesized to increase postmenopausal cardiometabolic risk. Although sleep disturbance, a known risk factor for cardiometabolic disease, is prevalent during the menopause transition, it is unknown whether menopause-related sleep disturbance and estradiol decline disturb the HPA axis.

OBJECTIVE

We examined the effect of experimental fragmentation of sleep and suppression of estradiol as a model of menopause on cortisol levels in healthy young women.

METHODS

Twenty-two women completed a 5-night inpatient study during the mid-to-late follicular phase (estrogenized). A subset (n = 14) repeated the protocol after gonadotropin-releasing hormone agonist-induced estradiol suppression. Each inpatient study included 2 unfragmented sleep nights followed by 3 experimental sleep fragmentation nights. This study took place with premenopausal women at an academic medical center. Interventions included sleep fragmentation and pharmacological hypoestrogenism, and main outcome measures were serum bedtime cortisol levels and cortisol awakening response (CAR).

RESULTS

Bedtime cortisol increased 27% (P = .03) and CAR decreased 57% (P = .01) following sleep fragmentation compared to unfragmented sleep. Polysomnographic-derived wake after sleep-onset (WASO) was positively associated with bedtime cortisol levels (P = .047) and negatively associated with CAR (P < .01). Bedtime cortisol levels were 22% lower in the hypoestrogenized state compared to the estrogenized state (P = .02), while CAR was similar in both estradiol conditions (P = .38).

CONCLUSION

Estradiol suppression and modifiable menopause-related sleep fragmentation both independently perturb HPA axis activity. Sleep fragmentation, commonly seen in menopausal women, may disrupt the HPA axis, which in turn may lead to adverse health effects as women age.

Social jetlag and dietary intake: A systematic review

The objective of the current systematic review was to critically review the available evidence regarding the link between social jetlag and diet among the general population using observational studies. Electronic databases, including PubMed, Scopus, and ISI Web of Sciences were searched systematically. We reviewed 348 references, of which 17 studies met inclusion criteria with a total sample size of 28,905. Qualitative analysis indicated a negative association between social jetlag and adherence to healthy eating habits, including a negative association with empirically-derived healthy dietary patterns, Japanese dietary patterns, Baltic Sea dietary patterns, and the Mediterranean diet, as well as a positive association with Meat and Starchy dietary pattern. On the other hand, the findings on the link of social jetlag with food groups and nutrients were mixed and controversial, except for a more consistent increase in sugar-sweetened beverages, total fat, and saturated fat intake. Our results indicate a possible link between social jetlag and dietary intake. Research suggests that individuals experiencing greater social jetlag exhibit reduced adherence to a healthy eating pattern. However, it is important to note that the reported association lacks consensus, emphasizing the need for additional longitudinal studies to gain further insights into this matter."

Sleep behavior traits and associations with opioid-related adverse events: a cohort study

STUDY OBJECTIVES

Opioid-related adverse events (OAEs), including opioid use disorders, overdose, and death, are serious public health concerns. OAEs are often associated with disrupted sleep, but the long-term relationship between poor sleep and subsequent OAE risk remains unknown. This study investigates whether sleep behavior traits are associated with incident OAEs in a large population cohort.

METHODS

444 039 participants (mean age ± SD 57 ± 8 years) from the UK Biobank reported their sleep behavior traits (sleep duration, daytime sleepiness, insomnia-like complaints, napping, and chronotype) between 2006 and 2010. The frequency/severity of these traits determined a poor sleep behavior impacts score (0-9). Incident OAEs were obtained from hospitalization records during 12-year median follow-up. Cox proportional hazards models examined the association between sleep and OAEs.

RESULTS

Short and long sleep duration, frequent daytime sleepiness, insomnia symptoms, and napping, but not chronotype, were associated with increased OAE risk in fully adjusted models. Compared to the minimal poor sleep behavior impacts group (scores of 0-1), the moderate (4-5) and significant (6-9) groups had hazard ratios of 1.47 (95% confidence interval [1.27, 1.71]), p < 0.001, and 2.19 ([1.82, 2.64], p < 0.001), respectively. The latter risk magnitude is greater than the risk associated with preexisting psychiatric illness or sedative-hypnotic medication use. In participants with moderate/significant poor sleep impacts (vs. minimal), subgroup analysis revealed that age <65 years was associated with a higher OAE risk than in those ≥65 years.

CONCLUSIONS

Certain sleep behavior traits and overall poor sleep impacts are associated with an increased risk for opioid-related adverse events.

Circadian misalignment increases 24-hour acylated ghrelin in chronic shift workers: a randomized crossover trial

OBJECTIVE

Shift workers typically experience misalignment between their circadian system and behavioral/environmental cycles and have an increased risk for obesity. Experimental studies in non-shift workers have suggested that circadian misalignment can disrupt energy balance regulation. This study examined the impact of circadian misalignment in the most relevant population, i.e., chronic shift workers.

METHODS

Seven healthy chronic night shift workers underwent a randomized crossover study with two 3-day laboratory protocols: a night work protocol including 12-hour inverted behavioral/environmental cycles (circadian misalignment) and a day work protocol (circadian alignment).

RESULTS

Circadian misalignment led to a ~17% increase in 24-hour acylated ghrelin levels in the chronic shift workers (p = 0.009). Consistently, circadian misalignment resulted in ~14% higher hunger at breakfast in the night shift (p = 0.04). Circadian misalignment did not significantly change fasting and postprandial energy expenditure or respiratory exchange ratio (all p > 0.32). Unexpectedly, 24-hour behavioral activity levels were ~38% higher (p < 0.0001) during circadian misalignment, despite a concurrent increase in sleepiness (p = 0.03).

CONCLUSIONS

These results reveal that circadian misalignment, while carefully controlling for dietary intake, increases acylated ghrelin in chronic shift workers. Further studies should test whether the observed acute effects of circadian misalignment in chronic shift workers contribute to their increased obesity risk in the long term.

CIRCUST: A novel methodology for temporal order reconstruction of molecular rhythms; validation and application towards a daily rhythm gene expression atlas in humans

The circadian system drives near-24-h oscillations in behaviors and biological processes. The underlying core molecular clock regulates the expression of other genes, and it has been shown that the expression of more than 50 percent of genes in mammals displays 24-h rhythmic patterns, with the specific genes that cycle varying from one tissue to another. Determining rhythmic gene expression patterns in human tissues sampled as single timepoints has several challenges, including the reconstruction of temporal order of highly noisy data. Previous methodologies have attempted to address these challenges in one or a small number of tissues for which rhythmic gene evolutionary conservation is assumed to be preserved. Here we introduce CIRCUST, a novel CIRCular-robUST methodology for analyzing molecular rhythms, that relies on circular statistics, is robust against noise, and requires fewer assumptions than existing methodologies. Next, we validated the method against four controlled experiments in which sampling times were known, and finally, CIRCUST was applied to 34 tissues from the Genotype-Tissue Expression (GTEx) dataset with the aim towards building a comprehensive daily rhythm gene expression atlas in humans. The validation and application shown here indicate that CIRCUST provides a flexible framework to formulate and solve the issues related to the analysis of molecular rhythms in human tissues. CIRCUST methodology is publicly available at https://github.com/yolandalago/CIRCUST/.

A Novel Home-Based Study of Circadian Rhythms: Design, Rationale, and Methods for the Circadia Study

The Circadia Study (Circadia) is a novel "direct-to-participant" research study investigating the genetics of circadian rhythm disorders of advanced and delayed sleep phase and non-24 hour rhythms. The goals of the Circadia Study are twofold: (i) to create an easy-to-use toolkit for at-home circadian phase assessment for patients with circadian rhythm disorders through the use of novel in-home based surveys, tests, and collection kits; and (ii) create a richly phenotyped patient resource for genetic studies that will lead to new genetic loci associated with circadian rhythm disorders revealing possible loci of interest to target in the development of therapeutics for circadian rhythm disorders. Through these goals, we aim to broaden our understanding and elucidate the genetics of circadian rhythm disorders across a diverse patient population while increasing accessibility to circadian rhythm disorder diagnostics reducing health disparities through self-directed at-home dim light melatonin onset (DLMO) collections.

Habitual nappers and non-nappers differ in circadian rhythms of LIPE expression in abdominal adipose tissue explants

Background and purpose

Napping is a widespread practice worldwide and has in recent years been linked to increased abdominal adiposity. Lipase E or LIPE encodes the protein hormone-sensitive lipase (HSL), an enzyme that plays an important role in lipid mobilization and exhibits a circadian expression rhythm in human adipose tissue. We hypothesized that habitual napping may impact the circadian expression pattern of LIPE, which in turn may attenuate lipid mobilization and induce abdominal fat accumulation.

Methods

Abdominal adipose tissue explants from participants with obesity (n = 17) were cultured for a 24-h duration and analyzed every 4 h. Habitual nappers (n = 8) were selected to match non-nappers (n = 9) in age, sex, BMI, adiposity, and metabolic syndrome traits. Circadian LIPE expression rhythmicity was analyzed using the cosinor method.

Results

Adipose tissue explants exhibited robust circadian rhythms in LIPE expression in non-nappers. In contrast, nappers had a flattened rhythm. LIPE amplitude was decreased in nappers as compared with non-nappers (71% lower). The decrease in amplitude among nappers was related to the frequency of napping (times per week) where a lower rhythm amplitude was associated with a higher napping frequency (r = -0.80; P = 0.018). Confirmatory analyses in the activity of LIPE's protein (i.e., HSL) also showed a significant rhythm in non-nappers, whereas significance in the activity of HSL was lost among nappers.

Conclusion

Our results suggest that nappers display dysregulated circadian LIPE expression as well as dysregulated circadian HSL activity, which may alter lipid mobilization and contribute to increased abdominal obesity in habitual nappers.

Association of Timing of Moderate-to-Vigorous Physical Activity With Changes in Glycemic Control Over 4 Years in Adults With Type 2 Diabetes From the Look AHEAD Trial

OBJECTIVE

We aimed to determine the association of the time-of-day of bout-related moderate-to-vigorous physical activity (bMVPA) with changes in glycemic control across 4 years in adults with overweight/obesity and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Among 2,416 participants (57% women; mean age, 59 years) with 7-day waist-worn accelerometry recording at year 1 or 4, we assigned bMVPA timing groups based on the participants' temporal distribution of bMVPA at year 1 and recategorized them at year 4. The time-varying exposure of bMVPA (≥10-min bout) timing was defined as ≥50% of bMVPA occurring during the same time period (morning, midday, afternoon, or evening), <50% of bMVPA in any time period (mixed), and ≤1 day with bMVPA per week (inactive).

RESULTS

HbA1c reduction at year 1 varied among bMVPA timing groups (P = 0.02), independent of weekly bMVPA volume and intensity. The afternoon group had the greatest HbA1c reduction versus inactive (-0.22% [95%CI -0.39%, -0.06%]), the magnitude of which was 30-50% larger than the other groups. The odds of discontinuation versus maintaining or initiating glucose-lowering medications at year 1 differed by bMVPA timing (P = 0.04). The afternoon group had the highest odds (odds ratio 2.13 [95% CI 1.29, 3.52]). For all the year-4 bMVPA timing groups, there were no significant changes in HbA1c between year 1 and 4.

CONCLUSION

bMVPA performed in the afternoon is associated with improvements in glycemic control in adults with diabetes, especially within the initial 12 months of an intervention. Experimental studies are needed to examine causality.

Best Time of Day for Strength and Endurance Training to Improve Health and Performance? A Systematic Review with Meta-analysis

BACKGROUND

Current recommendations for physical exercise include information about the frequency, intensity, type, and duration of exercise. However, to date, there are no recommendations on what time of day one should exercise. The aim was to perform a systematic review with meta-analysis to investigate if the time of day of exercise training in intervention studies influences the degree of improvements in physical performance or health-related outcomes.

METHODS

The databases EMBASE, PubMed, Cochrane Library, and SPORTDiscus were searched from inception to January 2023. Eligibility criteria were that the studies conducted structured endurance and/or strength training with a minimum of two exercise sessions per week for at least 2 weeks and compared exercise training between at least two different times of the day using a randomized crossover or parallel group design.

RESULTS

From 14,125 screened articles, 26 articles were included in the systematic review of which seven were also included in the meta-analyses. Both the qualitative synthesis and the quantitative synthesis (i.e., meta-analysis) provide little evidence for or against the hypothesis that training at a specific time of day leads to more improvements in performance-related or health-related outcomes compared to other times. There was some evidence that there is a benefit when training and testing occur at the same time of day, mainly for performance-related outcomes. Overall, the risk of bias in most studies was high.

CONCLUSIONS

The current state of research provides evidence neither for nor against a specific time of the day being more beneficial, but provides evidence for larger effects when there is congruency between training and testing times. This review provides recommendations to improve the design and execution of future studies on this topic.

REGISTRATION

PROSPERO (CRD42021246468).

Associations of rest-activity rhythm disturbances with stroke risk and post-stroke adverse outcomes

Background

Almost all biological and disease processes are influenced by circadian clocks and display ∼24-hour rhythms. Disruption of these rhythms may be an important novel risk factor for stroke. We evaluated the association between 24-h rest-activity rhythm measures, stroke risk, and major post-stroke adverse outcomes.

Methods

In this cohort study, we examined ∼100,000 participants in the UK Biobank (44-79 years old; ∼57% females) who underwent an actigraphy (6-7 days) and 5-year median follow-up. We derived: (1) most active 10 hours activity counts ( M10 ) across the 24-h cycle and the timing of its midpoint ( M10 midpoint ); (2) the least active 5 hours counts ( L5 ) and its midpoint timing ( L5 midpoint ); (3) relative amplitude ( RA ) - (M10-L5)/(M10+L5); (4) interdaily stability (IS): stability and (5) intradaily variability (IV), fragmentation of the rhythm. Cox proportional hazard models were constructed for time to (i) incident stroke (n=1,652); and (ii) post-stroke adverse outcomes (dementia, depression, disability, or death).

Results

Suppressed RA (lower M10 and higher L5) was associated with stroke risk after adjusting for demographics; the risk was highest in the lowest quartile [Q1] for RA (HR=1.62; 95% CI:1.36-1.93, p <0.001) compared to the top quartile [Q4]. Participants with later M10 midpoint timing (14:00-15:26, HR=1.26, CI:1.07-1.49, p =0.007) also had a higher risk for stroke than earlier (12:17-13:10) participants. A fragmented rhythm (IV) was also associated with a higher risk for stroke (Q4 vs. Q1; HR=1.27; CI:1.06-1.50, p =0.008), but differences in the stability of rhythms (IS) were not. Suppressed RA was associated with an increased risk of unfavorable post-stroke outcomes (Q1 vs. Q4; 1.78 [1.29-2.47]; p <0.001). All the associations were independent of age, sex, race, obesity, sleep disorders, cardiovascular diseases or risks, and other morbidity burdens.

Conclusion

Suppressed 24-h rest-activity rhythm may be a risk factor for stroke and an early indicator of major post-stroke adverse outcomes.

Lifestyle mediators of associations among siestas, obesity, and metabolic health

OBJECTIVE

The aim of this study was to determine the association between siestas/no siestas and obesity, considering siesta duration (long: >30 minutes, short: ≤30 minutes), and test whether siesta traits and/or lifestyle factors mediate the association of siestas with obesity and metabolic syndrome (MetS).

METHODS

This was a cross-sectional study of 3275 adults from a Mediterranean population (the Obesity, Nutrigenetics, TIming, and MEditerranean [ONTIME] study) who had the opportunity of taking siestas because it is culturally embedded.

RESULTS

Thirty-five percent of participants usually took siestas (16% long siestas). Compared with the no-siesta group, long siestas were associated with higher values of BMI, waist circumference, fasting glucose, systolic blood pressure, and diastolic blood pressure, as well as with a higher prevalence of MetS (41%; p = 0.015). In contrast, the probability of having elevated SBP was lower in the short-siesta group (21%; p = 0.044) than in the no-siesta group. Smoking a higher number of cigarettes per day mediated the association of long siestas with higher BMI (by 12%, percentage of association mediated by smoking; p < 0.05). Similarly, delays in nighttime sleep and eating schedules and higher energy intake at lunch (the meal preceding siestas) mediated the association between higher BMI and long siestas by 8%, 4%, and 5% (all p < 0.05). Napping in bed (vs. sofa/armchair) showed a trend to mediate the association between long siestas and higher SBP (by 6%; p = 0.055).

CONCLUSIONS

Siesta duration is relevant in obesity/MetS. Timing of nighttime sleep and eating, energy intake at lunch, cigarette smoking, and siesta location mediated this association.

Evening types as determined by subjective and objective measures are more emotional eaters

OBJECTIVE

This study aimed to determine the association between being an evening type (ET; defined subjectively by the Morning-Evening Questionnaire or objectively by the dim-light melatonin onset [DLMO] timing) and reporting emotional eating (EE) behaviors.

METHODS

Cross-sectional analyses were conducted in 3964 participants (four international cohorts: ONTIME and ONTIME-MT [both Spain], SHIFT [the US], and DICACEM [Mexico]), in which chronotype (Morning-Evening Questionnaire), EE behaviors (Emotional Eating Questionnaire), and dietary habits (dietary records or food-frequency questionnaire) were assessed. Among 162 participants (ONTIME-MT subsample), additional measures of DLMO (physiological gold standard of circadian phase) were available.

RESULTS

In three populations, ETs presented with a higher EE score than morning types (p < 0.02); and they made up a higher proportion of emotional eaters (p < 0.01). ETs presented with higher scores on disinhibition/overeating as well as food craving factors and experienced these behaviors more frequently than morning types (p < 0.05). Furthermore, a meta-analysis showed that being an ET was associated with a higher EE score by 1.52 points of a total of 30 points (95% CI: 0.89-2.14). The timing of DLMO in the early, intermediate, and late objective chronotypes occurred at 21:02 h, 22:12 h, and 23:37 h, with late types showing a higher EE score (p = 0.043).

CONCLUSIONS

Eveningness associated with EE in populations with different cultural, environmental, and genetic backgrounds. Individuals with late DLMO also showed more EE.

Heart rate response and recovery during exercise predict future delirium risk-A prospective cohort study in middle- to older-aged adults

BACKGROUND

Delirium is a neurocognitive disorder characterized by an abrupt decline in attention, awareness, and cognition after surgical/illness-induced stressors on the brain. There is now an increasing focus on how cardiovascular health interacts with neurocognitive disorders given their overlapping risk factors and links to subsequent dementia and mortality. One common indicator for cardiovascular health is the heart rate response/recovery (HRR) to exercise, but how this relates to future delirium is unknown.

METHODS

Electrocardiogram data were examined in 38,740 middle- to older-aged UK Biobank participants (mean age = 58.1 years, range: 40-72 years; 47.3% males) who completed a standardized submaximal exercise stress test (15-s baseline, 6-min exercise, and 1-min recovery) and required hospitalization during follow-up. An HRR index was derived as the product of the heart rate (HR) responses during exercise (peak/resting HRs) and recovery (peak/recovery HRs) and categorized into low/average/high groups as the bottom quartile/middle 2 quartiles/top quartile, respectively. Associations between 3 HRR groups and new-onset delirium were investigated using Cox proportional hazards models and a 2-year landmark analysis to minimize reverse causation. Sociodemographic factors, lifestyle factors/physical activity, cardiovascular risk, comorbidities, cognition, and maximal workload achieved were included as covariates.

RESULTS

During a median follow-up period of 11 years, 348 participants (9/1000) newly developed delirium. Compared with the high HRR group (16/1000), the risk for delirium was almost doubled in those with low HRR (hazard ratio = 1.90, 95% confidence interval (95%CI): 1.30-2.79, p = 0.001) and average HRR (hazard ratio = 1.54, 95%CI: 1.07-2.22, p = 0.020)). Low HRR was equivalent to being 6 years older, a current smoker, or ≥3 additional cardiovascular disease risks. Results were robust in sensitivity analysis, but the risk appeared larger in those with better cognition and when only postoperative delirium was considered (n = 147; hazard ratio = 2.66, 95%CI: 1.46-4.85, p = 0.001).

CONCLUSION

HRR during submaximal exercise is associated with future risk for delirium. Given that HRR is potentially modifiable, it may prove useful for neurological risk stratification alongside traditional cardiovascular risk factors.

Circadian Rest-Activity Rhythms, Delirium Risk, and Progression to Dementia

OBJECTIVE

Delirium is a complex neurocognitive syndrome suspected to be bidirectionally linked to dementia. Circadian rhythm disturbances likely contribute to dementia pathogenesis, but whether these disturbances are related to delirium risk and progression to all-cause dementia is unknown.

METHODS

We analyzed continuous actigraphy data from 53,417 middle-aged or older UK Biobank participants during a median 5 years of follow-up. Four measures were used to characterize the 24-hour daily rest-activity rhythms (RARs): normalized amplitude, acrophase representing the peak activity time, interdaily stability, and intradaily variability (IV) for fragmentation of the rhythm. Cox proportional hazards models examined whether RARs predicted incident delirium (n = 551) and progression to dementia (n = 61).

RESULTS

Suppressed 24-hour amplitude, lowest (Q1) versus highest (Q4) quartile (hazard ratio [HR]_{Q1 vs Q4} = 1.94, 95% confidence interval [CI] = 1.53-2.46, p < 0.001), and more fragmented (higher IV: HR_{Q4 vs Q1} = 1.49, 95% CI = 1.18-1.88, p < 0.001) rhythms predicted higher delirium risk, after adjusting for age, sex, education, cognitive performance, sleep duration/disturbances, and comorbidities. In those free from dementia, each hour of delayed acrophase was associated with delirium risk (HR = 1.13, 95% CI = 1.04-1.23, p = 0.003). Suppressed 24-hour amplitude was associated with increased risk of progression from delirium to new onset dementia (HR = 1.31, 95% CI = 1.03-1.67, p = 0.03 for each 1-standard deviation decrease).

INTERPRETATION

Twenty-four-hour daily RAR suppression, fragmentation, and potentially delayed acrophase were associated with delirium risk. Subsequent progression to dementia was more likely in delirium cases with suppressed rhythms. The presence of RAR disturbances before delirium and prior to progression to dementia suggests that these disturbances may predict higher risk and be involved in early disease pathogenesis. ANN NEUROL 2023.

Desynchronizing the sleep---wake cycle from circadian timing to assess their separate contributions to physiology and behaviour and to estimate intrinsic circadian period

Circadian clocks drive cyclic variations in many aspects of physiology, but some daily variations are evoked by periodic changes in the environment or sleep-wake state and associated behaviors, such as changes in posture, light levels, fasting or eating, rest or activity and social interactions; thus, it is often important to quantify the relative contributions of these factors. Yet, circadian rhythms and these evoked effects cannot be separated under typical 24-h day conditions, because circadian phase and the length of time awake or asleep co-vary. Nathaniel Kleitman's forced desynchrony (FD) protocol was designed to assess endogenous circadian rhythmicity and to separate circadian from evoked components of daily rhythms in multiple parameters. Under FD protocol conditions, light intensity is kept low to minimize its impact on the circadian pacemaker, and participants have sleep-wake state and associated behaviors scheduled to an imposed non-24-h cycle. The period of this imposed cycle, Τ, is chosen so that the circadian pacemaker cannot entrain to it and therefore continues to oscillate at its intrinsic period (τ, ~24.15 h), ensuring circadian components are separated from evoked components of daily rhythms. Here we provide detailed instructions and troubleshooting techniques on how to design, implement and analyze the data from an FD protocol. We provide two procedures: one with general guidance for designing an FD study and another with more precise instructions for replicating one of our previous FD studies. We discuss estimating circadian parameters and quantifying the separate contributions of circadian rhythmicity and the sleep-wake cycle, including statistical analysis procedures and an R package for conducting the non-orthogonal spectral analysis method that enables an accurate estimation of period, amplitude and phase.

Genetics of circadian rhythms and sleep in human health and disease

Circadian rhythms and sleep are fundamental biological processes integral to human health. Their disruption is associated with detrimental physiological consequences, including cognitive, metabolic, cardiovascular and immunological dysfunctions. Yet many of the molecular underpinnings of sleep regulation in health and disease have remained elusive. Given the moderate heritability of circadian and sleep traits, genetics offers an opportunity that complements insights from model organism studies to advance our fundamental molecular understanding of human circadian and sleep physiology and linked chronic disease biology. Here, we review recent discoveries of the genetics of circadian and sleep physiology and disorders with a focus on those that reveal causal contributions to complex diseases.

Research gaps and opportunities in precision nutrition: an NIH workshop report

Precision nutrition is an emerging concept that aims to develop nutrition recommendations tailored to different people's circumstances and biological characteristics. Responses to dietary change and the resulting health outcomes from consuming different diets may vary significantly between people based on interactions between their genetic backgrounds, physiology, microbiome, underlying health status, behaviors, social influences, and environmental exposures. On 11-12 January 2021, the National Institutes of Health convened a workshop entitled "Precision Nutrition: Research Gaps and Opportunities" to bring together experts to discuss the issues involved in better understanding and addressing precision nutrition. The workshop proceeded in 3 parts: part I covered many aspects of genetics and physiology that mediate the links between nutrient intake and health conditions such as cardiovascular disease, Alzheimer disease, and cancer; part II reviewed potential contributors to interindividual variability in dietary exposures and responses such as baseline nutritional status, circadian rhythm/sleep, environmental exposures, sensory properties of food, stress, inflammation, and the social determinants of health; part III presented the need for systems approaches, with new methods and technologies that can facilitate the study and implementation of precision nutrition, and workforce development needed to create a new generation of researchers. The workshop concluded that much research will be needed before more precise nutrition recommendations can be achieved. This includes better understanding and accounting for variables such as age, sex, ethnicity, medical history, genetics, and social and environmental factors. The advent of new methods and technologies and the availability of considerably more data bring tremendous opportunity. However, the field must proceed with appropriate levels of caution and make sure the factors listed above are all considered, and systems approaches and methods are incorporated. It will be important to develop and train an expanded workforce with the goal of reducing health disparities and improving precision nutritional advice for all Americans.

Keeping an eye on circadian time in clinical research and medicine

BACKGROUND

Daily rhythms are observed in humans and almost all other organisms. Most of these observed rhythms reflect both underlying endogenous circadian rhythms and evoked responses from behaviours such as sleep/wake, eating/fasting, rest/activity, posture changes and exercise. For many research and clinical purposes, it is important to understand the contribution of the endogenous circadian component to these observed rhythms.

CONTENT

The goal of this manuscript is to provide guidance on best practices in measuring metrics of endogenous circadian rhythms in humans and promote the inclusion of circadian rhythms assessments in studies of health and disease. Circadian rhythms affect all aspects of physiology. By specifying minimal experimental conditions for studies, we aim to improve the quality, reliability and interpretability of research into circadian and daily (i.e., time-of-day) rhythms and facilitate the interpretation of clinical and translational findings within the context of human circadian rhythms. We describe protocols, variables and analyses commonly used for studying human daily rhythms, including how to assess the relative contributions of the endogenous circadian system and other daily patterns in behaviours or the environment. We conclude with recommendations for protocols, variables, analyses, definitions and examples of circadian terminology.

CONCLUSION

Although circadian rhythms and daily effects on health outcomes can be challenging to distinguish in practice, this distinction may be important in many clinical settings. Identifying and targeting the appropriate underlying (patho)physiology is a medical goal. This review provides methods for identifying circadian effects to aid in the interpretation of published work and the inclusion of circadian factors in clinical research and practice.

Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity

Late eating has been linked to obesity risk. It is unclear whether this is caused by changes in hunger and appetite, energy expenditure, or both, and whether molecular pathways in adipose tissues are involved. Therefore, we conducted a randomized, controlled, crossover trial (ClinicalTrials.gov NCT02298790) to determine the effects of late versus early eating while rigorously controlling for nutrient intake, physical activity, sleep, and light exposure. Late eating increased hunger (p < 0.0001) and altered appetite-regulating hormones, increasing waketime and 24-h ghrelin:leptin ratio (p < 0.0001 and p = 0.006, respectively). Furthermore, late eating decreased waketime energy expenditure (p = 0.002) and 24-h core body temperature (p = 0.019). Adipose tissue gene expression analyses showed that late eating altered pathways involved in lipid metabolism, e.g., p38 MAPK signaling, TGF-β signaling, modulation of receptor tyrosine kinases, and autophagy, in a direction consistent with decreased lipolysis/increased adipogenesis. These findings show converging mechanisms by which late eating may result in positive energy balance and increased obesity risk.

A matter of time: A systematic scoping review on a potential role of the circadian system in binge eating behavior

Background

Emerging research suggests that food intake timing, eating behavior and food preference are associated with aspects of the circadian system function but the role that the circadian system may play in binge eating (BE) behavior in humans remains unclear.

Objective

To systematically evaluate the evidence for circadian system involvement in BE behavior.

Methods

Systematic searches of PubMed, EMBASE, and Scopus were performed for reports published from inception until May 2020 (PROSPERO Registration CRD42020186325). Searches were conducted by combining Medical Subject Headings related to the circadian system, BE behavior, and/or interventions. Observational and interventional studies in humans with BE behavior published in peer-review journals in the English language were included. Studies were assessed using quality and risk of bias tools (AXIS, ROB 2.0, or ROBINS).

Results

The search produced 660 articles, 51 of which were included in this review. Of these articles, 46 were observational studies and 5 were interventional trials. Evidence from these studies suggests that individuals with BE behavior tend to have more food intake, more binge cravings, and more BE episodes later in the day. Hormonal and day/night locomotor activity rhythm disturbances may be associated with BE behavior. Furthermore, late diurnal preference ("eveningness") was associated with BE behavior and chronobiological interventions that shift the circadian clock earlier (e.g., morning bright light therapy) were found to possibly decrease BE behavior. Substantive clinical overlap exists between BE and night eating behavior. However, there is a significant knowledge gap regarding their potential relationship with the circadian system. Limitations include the lack of studies that use best-established techniques to assess the chronobiology of BE behavior, heterogeneity of participants, diagnostic criteria, and study design, which preclude a meta-analytic approach.

Conclusion

Current evidence, although limited, suggests that the circadian system may play a role in the etiology of BE behavior. Further mechanistic studies are needed to fully characterize a potential role of the circadian system in BE behavior. A chronobiological approach to studying BE behavior may lead to identification of its neurobiological components and development of novel therapeutic interventions.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020186325], identifier [CRD42020186325].

Sleep Fragmentation and Estradiol Suppression Decrease Fat Oxidation in Premenopausal Women

CONTEXT

Body fat gain associated with menopause has been attributed to estradiol (E2) withdrawal. Hypoestrogenism is unlikely to be the only contributing factor, however.

OBJECTIVE

Given the links between sleep and metabolic health, we examined the effects of an experimental menopausal model of sleep fragmentation on energy metabolism.

METHODS

Twenty premenopausal women (age 21-45 years) underwent a 5-night inpatient study during the mid-to-late follicular phase (estrogenized; n = 20) and the same protocol was repeated in a subset of the participants (n = 9) following leuprolide-induced E2 suppression (hypo-estrogenized). During each 5-night study, there were 2 nights of unfragmented sleep followed by 3 nights of fragmented sleep. Indirect calorimetry was used to assess fasted resting energy expenditure (REE) and substrate oxidation.

RESULTS

Sleep fragmentation in the estrogenized state increased the respiratory exchange ratio (RER) and carbohydrate oxidation while decreasing fat oxidation (all P < 0.01). Similarly, in the hypo-estrogenized state without sleep fragmentation, RER and carbohydrate oxidation increased and fat oxidation decreased (all P < 0.01); addition of sleep fragmentation to the hypo-estrogenized state did not produce further effects beyond that observed for either intervention alone (P < 0.05). There were no effects of either sleep fragmentation or E2 state on REE.

CONCLUSION

Sleep fragmentation and hypoestrogenism each independently alter fasting substrate oxidation in a manner that may contribute to body fat gain. These findings are important for understanding mechanisms underlying propensity to body fat gain in women across the menopause transition.

Chronic circadian disruption on a high-fat diet impairs glucose tolerance

BACKGROUND

Nearly 14% of Americans experience chronic circadian disruption due to shift work, increasing their risk of obesity, diabetes, and other cardiometabolic disorders. These disorders are also exacerbated by modern eating habits such as frequent snacking and consumption of high-fat foods.

METHODS

We investigated the effects of recurrent circadian disruption (RCD) on glucose metabolism in C57BL/6 mice and in human participants exposed to non-24-h light-dark (LD) schedules vs. those on standard 24-h LD schedules. These LD schedules were designed to induce circadian misalignment between behaviors including rest/activity and fasting/eating with the output of the near-24-h central circadian pacemaker, while minimizing sleep loss, and were maintained for 12 weeks in mice and 3 weeks in humans. We examined interactions of these circadian-disrupted schedules compared to control 24-h schedules with a lower-fat diet (LFD, 13% in mouse and 25-27% in humans) and high-fat diet (HFD, 45% in mouse and 45-50% in humans). We also used young vs. older mice to determine whether they would respond differently to RCD.

RESULTS

When combined with a HFD, we found that RCD caused significant weight gain in mice and increased body fat in humans, and significantly impaired glucose tolerance and insulin sensitivity in both mice and humans, but this did not occur when RCD was combined with a LFD. This effect was similar in both young and older mice.

CONCLUSION

These results in both humans and a model organism indicate that circadian disruption has an adverse effect on metabolism among individuals eating a high-fat Western-style diet, even in the absence of significant sleep loss, and suggest that reducing dietary fat may protect against the metabolic consequences of a lifestyle (such as shift work) that involves chronic circadian disruption.

Association of Poor Sleep Burden in Middle Age and Older Adults With Risk for Delirium During Hospitalization

BACKGROUND

Delirium is a distressing neurocognitive disorder recently linked to sleep disturbances. However, the longitudinal relationship between sleep and delirium remains unclear. This study assessed the associations of poor sleep burden, and its trajectory, with delirium risk during hospitalization.

METHODS

About 321 818 participants from the UK Biobank (mean age 58 ± 8 years [SD]; range 37-74 years) reported (2006-2010) sleep traits (sleep duration, excessive daytime sleepiness, insomnia-type complaints, napping, and chronotype-a closely related circadian measure for sleep timing), aggregated into a sleep burden score (0-9). New-onset delirium (n = 4 775) was obtained from hospitalization records during a 12-year median follow-up. About 42 291 (mean age 64 ± 8 years; range 44-83 years) had repeat sleep assessment on average 8 years after their first.

RESULTS

In the baseline cohort, Cox proportional hazards models showed that moderate (aggregate scores = 4-5) and severe (scores = 6-9) poor sleep burden groups were 18% (hazard ratio = 1.18 [95% confidence interval: 1.08-1.28], p < .001) and 57% (1.57 [1.38-1.80], p < .001), more likely to develop delirium, respectively. The latter risk magnitude is equivalent to 2 additional cardiovascular risks. These findings appeared robust when restricted to postoperative delirium and after exclusion of underlying dementia. Higher sleep burden was also associated with delirium in the follow-up cohort. Worsening sleep burden (score increase ≥2 vs no change) further increased the risk for delirium (1.79 [1.23-2.62], p = .002) independent of their baseline sleep score and time lag. The risk was highest in those younger than 65 years at baseline (p for interaction <.001).

CONCLUSION

Poor sleep burden and worsening trajectory were associated with increased risk for delirium; promotion of sleep health may be important for those at higher risk.

Interplay of Dinner Timing and MTNR1B Type 2 Diabetes Risk Variant on Glucose Tolerance and Insulin Secretion: A Randomized Crossover Trial

OBJECTIVE

We tested whether the concurrence of food intake and elevated concentrations of endogenous melatonin, as occurs with late eating, results in impaired glucose control, in particular in carriers of the type 2 diabetes-associated G allele in the melatonin receptor-1B gene (MTNR1B).

RESEARCH DESIGN AND METHODS

In a Spanish natural late-eating population, a randomized, crossover study was performed. Each participant (n = 845) underwent two evening 2-h 75-g oral glucose tolerance tests following an 8-h fast: an early condition scheduled 4 h prior to habitual bedtime ("early dinner timing") and a late condition scheduled 1 h prior to habitual bedtime ("late dinner timing"), simulating an early and a late dinner timing, respectively. Differences in postprandial glucose and insulin responses between early and late dinner timing were determined using incremental area under the curve (AUC) calculated by the trapezoidal method.

RESULTS

Melatonin serum levels were 3.5-fold higher in the late versus early condition, with late dinner timing resulting in 6.7% lower insulin AUC and 8.3% higher glucose AUC. The effect of late eating impairing glucose tolerance was stronger in the MTNR1B G-allele carriers than in noncarriers. Genotype differences in glucose tolerance were attributed to reductions in β-cell function (P for interaction, Pint glucose area under the curve = 0.009, Pint corrected insulin response = 0.022, and Pint disposition index = 0.018).

CONCLUSIONS

Concurrently high endogenous melatonin and carbohydrate intake, as typical for late eating, impairs glucose tolerance, especially in MTNR1B G-risk allele carriers, attributable to insulin secretion defects.

How Accurately Can We Recall the Timing of Food Intake? A Comparison of Food Times from Recall-Based Survey Questions and Daily Food Records

BACKGROUND

There currently are no standard, low-cost, and validated methods to assess the timing of food intake.

OBJECTIVES

The aim of this study was to validate simple, recall-based questions that can characterize food timing in free-living populations.

METHODS

The concordance between recall-based survey questions and food times estimated from multiple daily food records was assessed in 249 generally healthy, free-living adults from the Shift Work, Heredity, Insulin, and Food Timing (SHIFT) Study. At baseline, participants were asked: "At what time do you first start and stop eating on weekdays/workdays and weekends/non-workdays?" and "At what time do you have your main meal on weekdays/workdays and weekends/non-workdays?" Participants were then asked to complete ≤14 d of food records noting the start time of each eating occasion. The timing of the first, last, and main (largest percentage calories) eating occasions were determined from food records. Wilcoxon matched pairs signed rank and Kendall's coefficient of concordance were used to compare differences and determine agreements between the methods for these food timing parameters, as well as for the midpoint between first and last eating occasion.

RESULTS

Eating occasions on work and free days showed significant agreements between the 2 methods, except for the main eating occasion on free days. Significant agreements were generally modest and ranged from 0.16 (workdays main eating occasion) to 0.45 (workdays first eating occasion). Generally, times based on recall were later than those estimated from food records, and the differences in estimated times were smaller on workdays compared with free days, and smaller for the first compared with the last eating occasion. Main eating occasions from food records often varied between lunch and dinner times, contributing to low concordance with recalled times.

CONCLUSIONS

Modest agreements were found between food times derived from simple, recall-based survey questions and food times estimated from multiple-day food records. Single administration of these questions can effectively characterize the overall timing of eating occasions within a population for chrononutrition research purposes.

Actigraphy-Based Sleep Detection: Validation with Polysomnography and Comparison of Performance for Nighttime and Daytime Sleep During Simulated Shift Work

PURPOSE

Actigraphy-based sleep detection algorithms were mostly validated using nighttime sleep, and their performance in detecting daytime sleep is unclear. We evaluated and compared the performance of Actiware and the Cole-Kripke algorithm (C-K) - two commonly used actigraphy-based algorithms - in detecting daytime and nighttime sleep.

PARTICIPANTS AND METHODS

Twenty-five healthy young adults were monitored by polysomnography and actigraphy during two in-lab protocols with scheduled nighttime and/or daytime sleep (within-subject design). Mixed-effect models were conducted to compare the sensitivity, specificity, and F1 score (a less-biased measure of accuracy) of Actiware (with low/medium/high threshold setting, separately) and C-K in detecting sleep epochs from actigraphy recordings during nighttime/daytime. t-tests and intraclass correlation coefficients were used to assess the agreement between actigraphy-based algorithms and polysomnography in scoring total sleep time (TST).

RESULTS

Sensitivity was similar between nighttime (Actiware: 0.93-0.99 across threshold settings; C-K: 0.61) and daytime sleep (Actiware: 0.93-0.99; C-K: 0.66) for both the C-K and Actiware (daytime/nighttime×algorithm interaction: p > 0.1). Specificity for daytime sleep was lower (Actiware: 0.35-0.54; C-K: 0.91) than that for nighttime sleep (Actiware: 0.37-0.62; C-K: 0.93; p = 0.001). Specificity was also higher for C-K than Actiware (p < 0.001), with no daytime/nighttime×algorithm interaction (p > 0.1). C-K had lower F1 (nighttime = 0.74; daytime = 0.77) than Actiware (nighttime = 0.95-0.98; daytime = 0.90-0.91) for both nighttime and daytime sleep (all p < 0.05). The daytime-nighttime difference in F1 was opposite for Actiware (daytime: 0.90-0.91; nighttime: 0.95-0.98) and C-K (daytime: 0.77; nighttime: 0.74; interaction p = 0.003). Bias in TST was lowest in Actiware (with medium-threshold) for nighttime sleep (underestimation of 5.99 min/8h) and in Actiware (with low-threshold) for daytime sleep (overestimation of 17.75 min/8h).

CONCLUSION

Daytime/nighttime sleep affected specificity and F1 but not sensitivity of actigraphy-based sleep scoring. Overall, Actiware performed better than the C-K algorithm. Actiware with medium-threshold was the least biased in estimating nighttime TST, and Actiware with low-threshold was the least biased in estimating daytime TST.

Proof-of-principle demonstration of endogenous circadian system and circadian misalignment effects on human oral microbiota

Circadian misalignment-the misalignment between the central circadian "clock" and behavioral and environmental cycles (including sleep/wake, fasting/eating, dark/light)-results in adverse cardiovascular and metabolic effects. Potential underlying mechanisms for these adverse effects include alterations in the orogastrointestinal microbiota. However, it remains unknown whether human oral microbiota has endogenous circadian rhythms (i.e., independent of sleep/wake, fasting/eating, and dark/light cycles) and whether circadian misalignment influences oral microbiota community composition. Healthy young individuals [27.3 ± 2.3 years (18-35 years), 4 men and 2 women, body-mass index range: 18-28 kg/m² ] were enrolled in a stringently controlled 14-day circadian laboratory protocol. This included a 32-h constant routine (CR) protocol (endogenous circadian baseline assessment), a forced desynchrony protocol with four 28-h "days" under ~3 lx to induce circadian misalignment, and a post-misalignment 40-h CR protocol. Microbiota assessments were performed on saliva samples collected every 4 h throughout both CR protocols. Total DNA was extracted and processed using high-throughput 16S ribosomal RNA gene amplicon sequencing. The relative abundance of specific oral microbiota populations, i.e., one of the five dominant phyla, and three of the fourteen dominant genera, exhibited significant endogenous circadian rhythms. Importantly, circadian misalignment dramatically altered the oral microbiota landscape, such that four of the five dominant phyla and eight of the fourteen dominant genera exhibited significant circadian misalignment effects. Moreover, circadian misalignment significantly affected the metagenome functional content of oral microbiota (inferred gene content analysis), as indicated by changes in specific functional pathways associated with metabolic control and immunity. Collectively, our proof-of-concept study provides evidence for endogenous circadian rhythms in human oral microbiota and show that even relatively short-term experimental circadian misalignment can dramatically affect microbiota community composition and functional pathways involved in metabolism and immune function. These proof-of-principle findings have translational relevance to individuals typically exposed to circadian misalignment, including night shift workers and frequent flyers.

Daytime eating prevents internal circadian misalignment and glucose intolerance in night work

Night work increases diabetes risk. Misalignment between the central circadian “clock” and daily behaviors, typical in night workers, impairs glucose tolerance, likely due to internal misalignment between central and peripheral circadian rhythms. Whether appropriate circadian alignment of eating can prevent internal circadian misalignment and glucose intolerance is unknown. In a 14-day circadian paradigm, we assessed glycemic control during simulated night work with either nighttime or daytime eating. Assessment of central (body temperature) and peripheral (glucose and insulin) endogenous circadian rhythms happened during constant routine protocols before and after simulated night work. Nighttime eating led to misalignment between central and peripheral (glucose) endogenous circadian rhythms and impaired glucose tolerance, whereas restricting meals to daytime prevented it. These findings offer a behavioral approach to preventing glucose intolerance in shift workers.

Chronic Sleep Restriction While Minimizing Circadian Disruption Does Not Adversely Affect Glucose Tolerance

Insufficient sleep, which has been shown to adversely affect metabolism, is generally associated with prolonged exposure to artificial light at night, a known circadian disruptor. There is growing evidence suggesting that circadian disruption adversely affects metabolism, yet few studies have attempted to evaluate the adverse metabolic effects of insufficient sleep while controlling for circadian disruption. We assessed postprandial glucose and insulin responses to a standard breakfast meal in healthy adults (n = 9) who underwent 3 weeks of chronic sleep restriction (CSR) in a 37-day inpatient study while minimizing circadian disruption by maintaining the same duration of light exposure each study day. We compared these results to findings from an earlier inpatient study which used a forced desynchrony (FD) protocol to assess the influence of 3 weeks of CSR combined with recurrent circadian disruption (RCD) on glycemic control in healthy adults (n = 21). CSR combined with RCD resulted in significantly elevated postprandial plasma glucose levels (p < 0.0001), while CSR with minimized circadian disruption had no adverse glycemic effects after 3 weeks of exposure (EXP). These results suggest that one mechanism by which sleep restriction impacts metabolism may be via concurrent circadian disruption.

Understanding Circadian Mechanisms of Sudden Cardiac Death: A Report From the National Heart, Lung, and Blood Institute Workshop, Part 2: Population and Clinical Considerations

Sudden cardiac death (SCD) is the sudden, unexpected death due to abrupt loss of heart function secondary to cardiovascular disease. In certain populations living with cardiovascular disease, SCD follows a distinct 24-hour pattern in occurrence, suggesting day/night rhythms in behavior, the environment, and endogenous circadian rhythms result in daily spans of increased vulnerability. The National Heart, Lung, and Blood Institute convened a workshop, Understanding Circadian Mechanisms of Sudden Cardiac Death to identify fundamental questions regarding the role of the circadian rhythms in SCD. Part 2 summarizes research gaps and opportunities in the areas of population and clinical research identified in the workshop. Established research supports a complex interaction between circadian rhythms and physiological responses that increase the risk for SCD. Moreover, these physiological responses themselves are influenced by several biological variables, including the type of cardiovascular disease, sex, age, and genetics, as well as environmental factors. The emergence of new noninvasive biotechnological tools that continuously measure key cardiovascular variables, as well as the identification of biomarkers to assess circadian rhythms, hold promise for generating large-scale human data sets that will delineate which subsets of individuals are most vulnerable to SCD. Additionally, these data will improve our understanding of how people who suffer from circadian disruptions develop cardiovascular diseases that increase the risk for SCD. Emerging strategies to identify new biomarkers that can quantify circadian health (eg, environmental, behavioral, and internal misalignment) may lead to new interventions and therapeutic targets to prevent the progression of cardiovascular diseases that cause SCD.

The endogenous circadian system worsens asthma at night independent of sleep and other daily behavioral or environmental cycles

Asthma often worsens at night. To determine if the endogenous circadian system contributes to the nocturnal worsening of asthma, independent of sleep and other behavioral and environmental day/night cycles, we studied patients with asthma (without steroid use) over 3 wk in an ambulatory setting (with combined circadian, environmental, and behavioral effects) and across the circadian cycle in two complementary laboratory protocols performed in dim light, which separated circadian from environmental and behavioral effects: 1) a 38-h "constant routine," with continuous wakefulness, constant posture, 2-hourly isocaloric snacks, and 2) a 196-h "forced desynchrony" incorporating seven identical recurring 28-h sleep/wake cycles with all behaviors evenly scheduled across the circadian cycle. Indices of pulmonary function varied across the day in the ambulatory setting, and both laboratory protocols revealed significant circadian rhythms, with lowest function during the biological night, around 4:00 AM, uncovering a nocturnal exacerbation of asthma usually unnoticed or hidden by the presence of sleep. We also discovered a circadian rhythm in symptom-based rescue bronchodilator use (β2-adrenergic agonist inhaler) whereby inhaler use was four times more likely during the circadian night than day. There were additive influences on asthma from the circadian system plus sleep and other behavioral or environmental effects. Individuals with the lowest average pulmonary function tended to have the largest daily circadian variations and the largest behavioral cycle effects on asthma. When sleep was modeled to occur at night, the summed circadian, behavioral/environmental cycle effects almost perfectly matched the ambulatory data. Thus, the circadian system contributes to the common nocturnal worsening of asthma, implying that internal biological time should be considered for optimal therapy.

Timing of chocolate intake affects hunger, substrate oxidation, and microbiota: A randomized controlled trial

Eating chocolate in the morning or in the evening/at night, may differentially affect energy balance and impact body weight due to changes in energy intake, substrate oxidation, microbiota (composition/function), and circadian-related variables. In a randomized controlled trial, postmenopausal females (n = 19) had 100 g of chocolate in the morning (MC), in the evening/at night (EC), or no chocolate (N) for 2 weeks and ate any other food ad libitum. Our results show that 14 days of chocolate intake did not increase body weight. Chocolate consumption decreased hunger and desire for sweets (P < .005), and reduced ad libitum energy intake by ~300 kcal/day during MC and ~150 kcal/day during EC (P = .01), but did not fully compensate for the extra energy contribution of chocolate (542 kcal/day). EC increased physical activity by +6.9%, heat dissipation after meals +1.3%, and carbohydrate oxidation by +35.3% (P < .05). MC reduced fasting glucose (4.4%) and waist circumference (-1.7%) and increased lipid oxidation (+25.6%). Principal component analyses showed that both timings of chocolate intake resulted in differential microbiota profiles and function (P < .05). Heat map of wrist temperature and sleep records showed that EC induced more regular timing of sleep episodes with lower variability of sleep onset among days than MC (60 min vs 78 min; P = .028). In conclusion, having chocolate in the morning or in the evening/night results in differential effects on hunger and appetite, substrate oxidation, fasting glucose, microbiota (composition and function), and sleep and temperature rhythms. Results highlight that the "when" we eat is a relevant factor to consider in energy balance and metabolism.

Blunted rest-activity rhythms link to higher body mass index and inflammatory markers in children

STUDY OBJECTIVES

Disturbances of rest-activity rhythms are associated with higher body mass index (BMI) in adults. Whether such relationship exists in children is unclear. We aimed to examine cross-sectional associations of rest-activity rhythm characteristics with BMI z-score and obesity-related inflammatory markers in school-age children.

METHODS

Participants included 411 healthy children (mean ± SD age 10.1 ± 1.3 years, 50.8% girls) from a Mediterranean area of Spain who wore wrist accelerometers for 7 consecutive days. Metrics of rest-activity rhythm were derived using both parametric and nonparametric approaches. Obesity-related inflammatory markers were measured in saliva (n = 121).

RESULTS

In a multivariable-adjusted model, higher BMI z-score is associated with less robust 24-h rest-activity rhythms as represented by lower relative amplitude (-0.16 [95% CI -0.29, -0.02] per SD, p = 0.02). The association between BMI z-score and relative amplitude persisted with additional adjustment for sleep duration, and attenuated after adjustment for daytime activity level. Less robust rest-activity rhythms were related to increased levels of several salivary pro-inflammatory markers, including C-reactive protein, which is inversely associated with relative amplitude (-32.6% [-47.8%, -12.9%] per SD), independently of BMI z-score, sleep duration, and daytime activity level.

CONCLUSION

Blunted rest-activity rhythms are associated with higher BMI z-score and salivary pro-inflammatory markers already at an early age. The association with BMI z-score seem to be independent of sleep duration, and those with pro-inflammatory markers further independent of BMI z-score and daytime activity. Novel intervention targets at an early age based on improving the strength of rest-activity rhythms may help to prevent childhood obesity and related inflammation.

CLINICAL TRIALS REGISTRATION

NCT02895282.

Circadian Biology and Stroke

Circadian biology modulates almost all aspects of mammalian physiology, disease, and response to therapies. Emerging data suggest that circadian biology may significantly affect the mechanisms of susceptibility, injury, recovery, and the response to therapy in stroke. In this review/perspective, we survey the accumulating literature and attempt to connect molecular, cellular, and physiological pathways in circadian biology to clinical consequences in stroke. Accounting for the complex and multifactorial effects of circadian rhythm may improve translational opportunities for stroke diagnostics and therapeutics.

Effect of Experimentally Induced Sleep Fragmentation and Hypoestrogenism on Fasting Nutrient Utilization in Pre-Menopausal Women

Background: Both sleep disturbance and menopause have independently been associated with weight gain in women. Possible mechanisms contributing to this weight gain may be changes in resting energy expenditure (REE) and/or nutrient utilization. Therefore, in the current study we aimed to examine the effects of experimentally induced sleep fragmentation and pharmacologic estradiol (E2) withdrawal on REE and nutrient utilization in the fasted state. Design: We studied pre-menopausal women during 5-night inpatient studies repeated in the mid-to-late follicular phase (high-E2; n=21) and following leuprolide-induced hypoestrogenism (low-E2; n=9 completed second visit). During each admission there were two nights of unfragmented sleep [8-h time in bed (TIB)] and three nights of fragmented sleep [9-h TIB]. Sleep was fragmented using an auditory stimulus delivered every 15 minutes that sustained wake for 2 minutes, producing 1 hour of wake after sleep onset. Study diets consisted of 3 meals and a snack each day and were iso-caloric across the two visits. REE and nutrient utilization were assessed in the fasted state via indirect calorimetry and compared between E2 states following unfragmented and fragmented sleep using linear mixed models. Results: Sleep fragmentation in the high-E2 state increased the respiratory quotient (RQ; +3%; p=0.03) with an accompanying increase in carbohydrate oxidation (+20%; p=0.02) and decrease in fat oxidation (-16%; p=0.03). The same effect was observed in response to E2-withdrawl during unfragmented sleep [increased RQ (+5%; p=0.01) and carbohydrate oxidation (+33%; p=0.01), and decreased fat oxidation (-26%; p=0.01)]. There was no additive effect of sleep fragmentation on nutrient utilization in the low-E2 state suggesting a possible ceiling (RQ and carbohydrate oxidation) and floor (fat oxidation) effect. There was no effect of sleep fragmentation or E2 state on REE. Conclusion: Both sleep fragmentation and hypoestrogenism were shown to alter fasting nutrient utilization, but not REE, in a manner that may contribute to weight gain in menopausal women. These findings are important for understanding weight gain during menopause, which is characterized by estrogen withdrawal and often accompanied by sleep disturbances.

Cross-Sectional and Prospective Associations of Rest-Activity Rhythms with Circulating Inflammatory Markers in Older Men

Chronic increases in pro-inflammatory cytokines in older adults, known as inflammaging, is an important risk factor for morbidity and mortality in the aging population. It has been suggested that circadian disruption may play a role in chronic inflammation, but there has been limited study that investigated the overall profile of 24-hour rest-activity rhythms in relation to inflammation using longitudinal data. In the Outcomes of Sleep Disorders in Older Men Study, we applied the extended cosine model to derive multiple rest-activity rhythm characteristics using multi-day actigraphy, and examined their associations with six inflammatory markers (i.e., CRP, IL-6, TNF-α, TNF-α-sRII, IL-1 β, IFN-γ) measured from fasting blood. We assessed both the cross-sectional association between rest-activity rhythms and inflammatory markers measured at baseline, and the prospective association between baseline rest-activity rhythms and changes in in inflammatory markers over 3.5 years of follow up. We found that multiple rest-activity characteristics, including lower amplitude and relative amplitude, and decreased overall rhythmicity, were associated with higher levels of CRP, IL-6, TNF-α, and TNF-α-sRII, but not IL-1β and IFN-γ at baseline. Moreover, the lowest quartile of these three rest-activity characteristics was associated with an approximately two-fold increase in the odds of having elevated inflammation (i.e. having three or more markers in the highest quartile) at baseline. However, we found little evidence supporting a relationship between rest-activity rhythm characteristics and changes in inflammatory markers. Future studies should clarify the dynamic relationship between rest-activity rhythms and inflammation in different populations, and evaluate the effects of improving rest-activity profiles on inflammation and related disease outcomes.

Association of Objectively Measured Timing of Physical Activity Bouts With Cardiovascular Health in Type 2 Diabetes

OBJECTIVE

Moderate- to vigorous-intensity physical activity (MVPA) improves cardiovascular health. Few studies have examined MVPA timing. We examined the associations of timing of bout-related MVPA with cardiorespiratory fitness and cardiovascular risk in adults with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Baseline 7-day hip-worn accelerometry data from Look AHEAD participants (n = 2,153, 57% women) were analyzed to identify bout-related MVPA (≥3 METs/min for ≥10 min). Cardiorespiratory fitness was assessed by maximal graded exercise test. Participants were categorized into six groups on the basis of the time of day with the majority of bout-related MVPA (METs × min): ≥50% of bout-related MVPA during the same time window (morning, midday, afternoon, or evening), <50% of bout-related MVPA in any time category (mixed; the reference group), and ≤1 day with bout-related MVPA per week (inactive).

RESULTS

Cardiorespiratory fitness was highly associated with timing of bout-related MVPA (P = 0.0005), independent of weekly bout-related MVPA volume and intensity. Importantly, this association varied by sex (P = 0.02). In men, the midday group had the lowest fitness (β = -0.46 [95% CI -0.87, -0.06]), while the mixed group in women was the least fit. Framingham risk score (FRS) was associated with timing of bout-related MVPA (P = 0.02), which also differed by sex (P = 0.0007). The male morning group had the highest 4-year FRS (2.18% [0.70, 3.65]), but no association was observed in women.

CONCLUSIONS

Timing of bout-related MVPA is associated with cardiorespiratory fitness and cardiovascular risk in men with type 2 diabetes, independent of bout-related MVPA volume and intensity. Prospective studies are needed to determine the impacts of MVPA timing on cardiovascular health.

Resting Heartbeat Complexity Predicts All-Cause and Cardiorespiratory Mortality in Middle- to Older-Aged Adults From the UK Biobank

Background

Spontaneous heart rate fluctuations contain rich information related to health and illness in terms of physiological complexity, an accepted indicator of plasticity and adaptability. However, it is challenging to make inferences on complexity from shorter, more practical epochs of data. Distribution entropy (DistEn) is a recently introduced complexity measure that is designed specifically for shorter duration heartbeat recordings. We hypothesized that reduced DistEn predicted increased mortality in a large population cohort.

Method and Results

The prognostic value of DistEn was examined in 7631 middle‐older–aged UK Biobank participants who had 2‐minute resting ECGs conducted (mean age, 59.5 years; 60.4% women). During a median follow‐up period of 7.8 years, 451 (5.9%) participants died. In Cox proportional hazards models with adjustment for demographics, lifestyle factors, physical activity, cardiovascular risks, and comorbidities, for each 1‐SD decrease in DistEn, the risk increased by 36%, 56%, and 73% for all‐cause, cardiovascular, and respiratory disease–related mortality, respectively. These effect sizes were equivalent to the risk of death from being >5 years older, having been a former smoker, or having diabetes mellitus. Lower DistEn was most predictive of death in those <55 years with a prior myocardial infarction, representing an additional 56% risk for mortality compared with older participants without prior myocardial infarction. These observations remained after controlling for traditional mortality predictors, resting heart rate, and heart rate variability.

Conclusions

Resting heartbeat complexity from short, resting ECGs was independently associated with mortality in middle‐ to older‐aged adults. These risks appear most pronounced in middle‐aged participants with prior MI, and may uniquely contribute to mortality risk screening.

Late eating is associated with cardiometabolic risk traits, obesogenic behaviors, and impaired weight loss

BACKGROUND

There is a paucity of evidence regarding the role of food timing on cardiometabolic health and weight loss in adults.

OBJECTIVES

To determine whether late eating is cross-sectionally associated with obesity and cardiometabolic risk factors at baseline; and whether late eating is associated with weight loss rate and success following a weight loss intervention protocol. Also, to identify obesogenic behaviors and weight loss barriers associated with late eating.

METHODS

Participants were recruited from a weight-loss program in Spain. Upon recruitment, the midpoint of meal intake was determined by calculating the midway point between breakfast and dinner times, and dietary composition was determined from diet recall. Population median for the midpoint of meal intake was used to stratify participants into early (before 14:54) and late (after 14:54) eaters. Cardiometabolic and satiety hormonal profiles were determined from fasting blood samples collected prior to intervention. Weekly weight loss and barriers were evaluated during the ∼19-wk program. Linear and logistic regression models were used to assess differences between late and early eaters in cardiometabolic traits, satiety hormones, obesogenic behaviors, and weight loss, adjusted for age, sex, clinic site, year of recruitment, and baseline BMI.

RESULTS

A total of 3362 adults [mean (SD): age: 41 (14) y; 79.2% women, BMI: 31.05 (5.58) kg/m2] were enrolled. At baseline, no differences were observed in energy intake or physical activity levels between early and late eaters (P >0.05). Late eaters had higher BMI, higher concentrations of triglycerides, and lower insulin sensitivity compared with early eaters (all P <0.05) prior to intervention. In addition, late eaters had higher concentrations of the satiety hormone leptin in the morning (P = 0.001). On average, late eaters had an average 80 g lower weekly rate of weight loss [early, 585 (667) g/wk; late, 505 (467) g/wk; P = 0.008], higher odds of having weight-loss barriers [OR (95% CI): 1.22 (1.03, 1.46); P = 0.025], and lower odds of motivation for weight loss [0.81 (0.66, 0.99); P = 0.044] compared with early eaters.

CONCLUSION

Our results suggest that late eating is associated with cardiometabolic risk factors and reduced efficacy of a weight-loss intervention. Insights into the characteristics and behaviors related to late eating may be useful in the development of future interventions aimed at advancing the timing of food intake.

Night shift work is associated with an increased risk of asthma

INTRODUCTION

Shift work causes misalignment between internal circadian time and the external light/dark cycle and is associated with metabolic disorders and cancer. Approximately 20% of the working population in industrialised countries work permanent or rotating night shifts, exposing this large population to the risk of circadian misalignment-driven disease. Analysis of the impact of shift work on chronic inflammatory diseases is lacking. We investigated the association between shift work and asthma.

METHODS

We describe the cross-sectional relationship between shift work and prevalent asthma in >280000 UK Biobank participants, making adjustments for major confounding factors (smoking history, ethnicity, socioeconomic status, physical activity, body mass index). We also investigated chronotype.

RESULTS

Compared with day workers, 'permanent' night shift workers had a higher likelihood of moderate-severe asthma (OR 1.36 (95% CI 1.03 to 1.8)) and all asthma (OR 1.23 (95% CI 1.03 to 1.46)). Individuals doing any type of shift work had higher adjusted odds of wheeze/whistling in the chest. Shift workers who never or rarely worked on nights and people working permanent nights had a higher adjusted likelihood of having reduced lung function (FEV1 <80% predicted). We found an increase in the risk of moderate-severe asthma in morning chronotypes working irregular shifts, including nights (OR 1.55 (95% CI 1.06 to 2.27)).

CONCLUSIONS

The public health implications of these findings are far-reaching due to the high prevalence and co-occurrence of both asthma and shift work. Future longitudinal follow-up studies are needed to determine if modifying shift work schedules to take into account chronotype might present a public health measure to reduce the risk of developing inflammatory diseases such as asthma.

Circadian Rhythms in Hormone-sensitive Lipase in Human Adipose Tissue: Relationship to Meal Timing and Fasting Duration

BACKGROUND

Fat mobilization in adipose tissue (AT) has a specific timing. However, circadian rhythms in the activity of the major enzyme responsible for fat mobilization, hormone-sensitive lipase (HSL), have not been demonstrated in humans.

OBJECTIVE

To analyze in a cross-sectional study whether there is an endogenous circadian rhythm in HSL activity in human AT ex vivo and whether rhythm characteristics are related to food timing or fasting duration.

METHODS

Abdominal AT biopsies were obtained from 18 severely obese participants (age: 46 ± 11 years; body mass index 42 ± 6 kg/m2) who underwent laparoscopic gastric bypass. Twenty-four-hour rhythms of HSL activity and LIPE (HSL transcript in humans) expression in subcutaneous AT were analyzed together with habitual food timing and night fasting duration.

RESULTS

HSL activity exhibited a circadian rhythm (P = .023) and reached the maximum value at circadian time 16 (CT) that corresponded to around midnight (relative local clock time. Similarly, LIPE displayed a circadian rhythm with acrophase also at night (P = .0002). Participants with longer night fasting duration >11.20 hours displayed almost double the amplitude (1.91 times) in HSL activity rhythm than those with short duration (P = .013); while habitual early diners (before 21:52 hours) had 1.60 times higher amplitude than late diners (P = .035).

CONCLUSIONS

Our results demonstrate circadian rhythms in HSL activity and may lead to a better understanding of the intricate relationships between food timing, fasting duration and body fat regulation.