Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study

Sleep and hypertension - up to date 2024

People spend one-third of their lives sleeping, and adequate, restful sleep is an essential component of a healthy life. Conversely, disruption of sleep has been found to cause various physical and mental health problems. Emerging research has shown that blood pressure (BP) during sleep is a stronger predictor of cardiovascular events than conventional office BP or daytime BP. Thus, management of both sleep health and nighttime BP during sleep is important for preventing cardiovascular events. However, recent studies demonstrated that nighttime BP is poorly controlled compared with office BP and daytime BP. This finding is understandable, given the challenges in monitoring BP during sleep and the multiplicity of factors related to nocturnal hypertension and BP variability. This review summarizes recent evidence and considers future perspectives for the management of sleep and hypertension.

Mental health, substance use, and a composite of sleep health in adults, 2018 Ohio behavioral risk factor surveillance system

OBJECTIVES

Various factors impact sleep health including mental health and substance use. Mental health issues and substance use continue to rise in the United States. Yet, the association between mental health, substance use and sleep health in adults remains unclear.

METHODS

We used multivariable linear regression models to examine the associations between mental health (poor mental health days in the past 30 days) and substance use (marijuana, tobacco, alcohol) with sleep health (individual dimensions of sleep: alertness, sleep efficiency, duration, and sleep health composite score) in 4333 participants from the 2018 Ohio Behavioral Risk Factor Surveillance System Survey.

RESULTS

Better mental health was associated with higher alertness, higher sleep efficiency, longer sleep duration and a higher sleep health composite score even after controlling for covariates (individual: sex at birth, age, body mass index, race, education, sleep disordered breathing, and area-level: socioeconomic deprivation) (all p < .001). Higher marijuana and tobacco use were associated with lower individual sleep health dimensions (marijuana with sleep efficiency and duration and tobacco use with lower efficiency) and a lower sleep health composite score even after controlling for covariates for tobacco use (p < .001). Contrary to the hypothesis, higher alcohol use was associated with higher alertness and a higher sleep health composite score (p < .001), however after adjusting for covariates these associations were no longer significant.

CONCLUSIONS

The implications of these trends on sleep health are important to address as mental health and substance use are modifiable targets to consider when addressing sleep health.

Sleep Irregularity and the Incidence of Type 2 Diabetes: A Device-Based Prospective Study in Adults

OBJECTIVE

To prospectively examine the association between device-measured sleep regularity and incidence of type 2 diabetes (T2D) in a population-based sample of adults. We also examined if meeting sleep duration recommendations attenuated or eliminated the effects of irregular sleep on T2D.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort study of adults aged 40-79 years participating in the UK Biobank accelerometer substudy. Participants wore wrist-attached accelerometers for a duration of 7 days, which was used to compute the Sleep Regularity Index (SRI). Participants were categorized as irregular (SRI <71.6), moderately irregular (SRI between 71.6 and 87.3), and regular (SRI >87.3) sleepers. T2D diagnosis was obtained through self-reports and health records.

RESULTS

We analyzed data from 73,630 individuals observed for 8 years, without a history of T2D and without an event in the first year of follow-up. Compared with regular sleepers, irregular (hazard ratio [HR] 1.38; 95% CI 1.20-1.59) and moderately irregular sleepers (HR 1.35; 95% CI 1.19-1.53) were at higher risk of T2D incidence. Dose-response analyses treating SRI as a continuous measure showed higher T2D incidence with SRI scores <80. Meeting current sleep duration recommendations did not counteract the adverse effects of irregular (HR 1.35; 95% CI 1.09-1.66) or moderately irregular (HR 1.29; 95% CI 1.08-1.54) sleep on T2D incidence.

CONCLUSIONS

Moderate and high sleep irregularity were deleteriously associated with T2D risk, even in participants who slept ≥7 h per night. Future sleep interventions will need to pay more attention to consistency in bedtimes and wake-up times, in addition to sleep duration and quality.

Sleep disturbances based on patient reported outcomes in patients with breast cancer

PURPOSE

Sleep disturbances are common in patients with breast cancer, but comprehensive evaluations with patient-reported outcomes (PRO) and sleep evaluation with polysomnography (PSG) are lacking. This study describes sleep disruption using PROs and PSG to identify underlying sleep disorders.

METHODS

A retrospective review of patients with breast cancer undergoing formal sleep evaluation from 4/1/2009 to 7/31/2014 was performed. Clinical characteristics, PROs using Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS), and PSG data were reviewed.

RESULTS

404 patients were identified with 43% early, 30% locally advanced and 17% metastatic disease. PSQI revealed poor sleep in 75%, and ESS demonstrated daytime sleepiness in 55%. Sleep aid use was reported by 39%, and pain medication use in 22%. Most patients (50.2%) had multiple sleep disorders. Insomnia (54.5%) was the most frequent sleep disorder, followed closely by obstructive sleep apnea (OSA) (53.7%). PSG was performed in 74%. Multivariate analysis linked poor sleep to use of sleep aids [OR 7.7, 95% CI 3.9 to 15.2], anxiety disorder [OR 4.8, 95% CI 1.7 to 14.0], and metastatic disease [OR 2.8, 95% CI 1.1 to 6.6]. Daytime sleepiness correlated with known diagnosis of OSA [OR 1.9, 95% CI 1.0 to 3.3] and sleep aid use [OR 0.6, 95% CI 0.4 to 0.9].

CONCLUSIONS

Poor sleep was associated with sleep aid use, anxiety disorder and metastatic disease. Insomnia was the most common sleep disorder, followed by OSA (mostly mild). Education about sleep health and proactive screening for sleep symptoms would be beneficial in patients with breast cancer.

Device-measured weekend catch-up sleep, mortality, and cardiovascular disease incidence in adults

STUDY OBJECTIVE

Attempting to recover a sleep debt by extending sleep over the weekend is a common compensatory behavior in the population and is recommended by sleep-focused organizations. However, the purported benefits of catch-up sleep are based on a limited number of cross-sectional studies that relied on self-reported sleep. The objective of this study was to examine the association between accelerometer-derived weekend catch-up sleep and mortality and incident cardiovascular disease (CVD) in adults.

METHODS

A prospective cohort study of UK adults who wore wrist-attached accelerometers was conducted. Weekend catch-up sleep was defined as a longer average sleep duration on weekends compared to weekdays. Participants were categorized into four groups: no weekend catch-up sleep (reference); > 0 to < 1 hour; ≥ 1 to < 2 hours; and ≥ 2 hours difference. Associations between weekend catch-up sleep and mortality and incident CVD were assessed using Cox proportional hazards regression, adjusted for potential confounders.

RESULTS

A total of 73 513 participants (sample for mortality) and 70 518 participants (sample for CVD incidence) were included, with an average (SD) follow-up period of 8.0 (0.9) years. In multivariable-adjusted models, weekend catch-up sleep was not associated with mortality (≥ 2 hours group: hazard ratio [HR], 1.17 [95% CI: 0.97 to 1.41]) or incident CVD (HR, 1.05 [95% CI, 0.94 to 1.18]). Dose-response analyses treating catch-up sleep as a continuous measure or analyses restricted to adults sleeping less than 6 hours on weekdays at baseline were in agreement with these findings.

CONCLUSIONS

Weekend catch-up sleep was not associated with mortality or CVD incidence. These findings do not align with previous evidence and recommendations by sleep authorities suggesting that extending sleep over the weekend may offer protective health benefits.

Sleep disorders and risk of alzheimer's disease: A two-way road

Substantial sleep impairment in patients with Alzheimer's disease (AD) is one of the emerging points for continued efforts to better understand the disease. Individuals without cognitive decline, an important marker of the clinical phase of AD, may show early alterations in the sleep-wake cycle. The objective of this critical narrative review is to explore the bidirectional pathophysiological correlation between sleep disturbances and Alzheimer's Disease. Specifically, it examines how the disruption of sleep homeostasis in individuals without dementia could contribute to the pathogenesis of AD, and conversely, how neurodegeneration in individuals with Alzheimer's Disease might lead to dysregulation of the sleep-wake cycle. Recent scientific results indicate that sleep disturbances, particularly those related to impaired glymphatic clearance, may act as an important mechanism associated with the genesis of Alzheimer's Disease. Additionally, amyloid deposition and tau protein hyperphosphorylation, along with astrocytic hyperactivation, appear to trigger changes in neurotransmission dynamics in areas related to sleep, which may explain the onset of sleep disturbances in individuals with AD. Disruption of sleep homeostasis appears to be a modifiable risk factor in Alzheimer's disease. Whenever possible, the use of non-pharmacological strategies becomes important in this context. From a different perspective, additional research is needed to understand and treat the dysfunction of the sleep-wake cycle in individuals already affected by AD. Early recognition and correction of sleep disturbances in this population could potentially mitigate the progression of dementia and improve the quality of life for those with AD.

Influence of sleep on physiological systems in atherosclerosis

Sleep is a fundamental requirement of life and is integral to health. Deviation from optimal sleep associates with numerous diseases including those of the cardiovascular system. Studies, spanning animal models to humans, show that insufficient, disrupted or inconsistent sleep contribute to poor cardiovascular health by disrupting body systems. Fundamental experiments have begun to uncover the molecular and cellular links between sleep and heart health while large-scale human studies have associated sleep with cardiovascular outcomes in diverse populations. Here, we review preclinical and clinical findings that demonstrate how sleep influences the autonomic nervous, metabolic and immune systems to affect atherosclerotic cardiovascular disease.

Correlates of sleep variability in a mobile EEG-based volunteer study

Variable sleep patterns are a risk factor for disease, but the reasons some people express greater within-individual variability of sleep characteristics remains poorly understood. In our study, we leverage BSETS, a novel mobile EEG-based dataset in which 1901 nights in total were recorded from 267 extensively phenotyped participants to identify factors related to demographics, mental health, personality, chronotype and sleep characteristics which predict variability in sleep, including detailed sleep macrostructure metrics. Young age, late chronotype, and napping emerged as robust correlates of increased sleep variability. Correlations with other characteristics (such as student status, personality, mental health and co-sleeping) generally disappeared after controlling for age. We critically examine the utility of controlling the correlates of sleep variability for the means of sleep variables. Our research shows that age and sleep habits affecting the amount of sleep pressure at night are the most important factors underlying sleep variability, with a smaller role of other psychosocial variables. The avoidance of daytime naps emerges as the most promising modifiable behavior associated with increased sleep regularity.

Brighter nights and darker days predict higher mortality risk: A prospective analysis of personal light exposure in >88,000 individuals

Light enhances or disrupts circadian rhythms, depending on the timing of exposure. Circadian disruption contributes to poor health outcomes that increase mortality risk. Whether personal light exposure predicts mortality risk has not been established. We therefore investigated whether personal day and night light, and light patterns that disrupt circadian rhythms, predicted mortality risk. UK Biobank participants (N = 88,905, 62.4 ± 7.8 y, 57% female) wore light sensors for 1 wk. Day and night light exposures were defined by factor analysis of 24-h light profiles. A computational model of the human circadian pacemaker was applied to model circadian amplitude and phase from light data. Cause-specific mortality was recorded in 3,750 participants across a mean (±SD) follow-up period of 8.0 ± 1.0 y. Individuals with brighter day light had incrementally lower all-cause mortality risk (adjusted-HR ranges: 0.84 to 0.90 [50 to 70th light exposure percentiles], 0.74 to 0.84 [70 to 90th], and 0.66 to 0.83 [90 to 100th]), and those with brighter night light had incrementally higher all-cause mortality risk (aHR ranges: 1.15 to 1.18 [70 to 90th], and 1.21 to 1.34 [90 to 100th]), compared to individuals in darker environments (0 to 50th percentiles). Individuals with lower circadian amplitude (aHR range: 0.90 to 0.96 per SD), earlier circadian phase (aHR range: 1.16 to 1.30), or later circadian phase (aHR range: 1.13 to 1.20) had higher all-cause mortality risks. Day light, night light, and circadian amplitude predicted cardiometabolic mortality, with larger hazard ratios than for mortality by other causes. Findings were robust to adjustment for age, sex, ethnicity, photoperiod, and sociodemographic and lifestyle factors. Minimizing night light, maximizing day light, and keeping regular light-dark patterns that enhance circadian rhythms may promote cardiometabolic health and longevity.

Diurnal patterns of accelerometer-measured physical activity and sleep and risk of all-cause mortality: a follow-up of the National Health and Nutrition Examination Surveys (NHANES)

BACKGROUND

Physical activity and sleep are established modifiable lifestyle factors, but the optimal time of the day of these behaviours for health is unknown. This study examined the independent and joint associations of diurnal patterns of physical activity and sleep with all-cause mortality.

METHODS

This prospective cohort study included 6,673 participants who have attended the accelerometer assessment in the 2011-2014 National Health and Nutrition Examination Surveys (NHANES). Diurnal patterns of accelerometer-measured physical activity and sleep were identified using K-means clustering analysis. All-cause mortality was ascertained from the accelerometer measurement to December 31, 2019 (median follow-up 6.8 years). Survey-weighted Cox proportional hazard models were performed to estimate the independent and joint associations of diurnal patterns of physical activity and sleep with all-cause mortality.

RESULTS

Diurnal patterns identified were: early-morning (32.4%), midday (42.5%), and late-afternoon (25.1%) for physical activity; and irregular sleep (37.4%), morning lark (33.6%), and night owl (29.0%) for sleep. After adjusting for volume of physical activity, sleep duration and other potential covariates, the early-morning physical activity pattern (hazard ratio 1.36, 95% confidence interval 1.13-1.64) and irregular sleep pattern (1.42, 1.01-1.99) were independently associated with higher risk of all-cause mortality, compared with midday physical activity and morning lark sleep patterns, respectively. In addition, participants with the combined pattern of early-morning physical activity and irregular sleep had higher risk of all-cause mortality compared to those with midday physical activity combined with a morning lark sleep pattern (1.92, 1.33-2.78). Several sociodemographic differences were observed in the strength of these associations.

CONCLUSIONS

Wearable activity-rest monitoring data showed that peak physical activity in the early morning and irregular sleep diurnal patterns are associated with increased mortality risk, and the combination of these patterns further exaggerated the risk. Public health program should acknowledge that the diurnal patterns of physical activity and sleep, in addition to their duration and frequency, may play a crucial role in lifestyle-based health promotion and management strategies.

Sleep, Well-Being, and Cognition in Medical Interns on a Float or Overnight Call Schedule

Importance

Extended work hours and night shifts are essential in health care, but negatively affect physician sleep, well-being, and patient care. Alternative schedules with shorter work hours and/or reduced irregularity might mitigate these issues.

Objective

To compare sleep, well-being, and cognition between interns working irregular, extended shifts (call schedule), and those working a more regular schedule with restricted hours (float schedule).

Design, Setting, and Participants

In this observational longitudinal cohort study, interns in a Singapore-based teaching hospital were studied for 8 weeks from January 2022 to July 2023. Data were analyzed from July 2023 to July 2024.

Exposure

Participants worked either regular approximately 10-hour workdays, interspersed with 24 hour or more overnight calls 4 to 5 times a month, or a float schedule, which included regular approximately 10-hour workdays, and 5 to 7 consecutive approximately 12-hour night shifts every 2 months. Exposure was based on departmental training and operational needs.

Main Outcomes and Measures

Sleep was measured with wearable sleep trackers and an electronic diary. Day-to-day well-being and cognitive assessments were collected through a smartphone application. Assessments included the Sleep Regularity Index (SRI; determines the probability of an individual being in the same state [sleep or wake] at any 2 time points 24 hours apart, with 0 indicating highly random sleep patterns and 100 denoting perfect regularity) and Pittsburgh Sleep Quality Inventory (PSQI; scores ranges from 0 to 21, with higher scores indicating poorer sleep; a score greater than 5 suggests significant sleep difficulties).

Results

Participants (mean [SD] age, 24.7 [1.1] years; 57 female participants [59.4%]; 41 on call schedule [42.7%]; 55 on float schedule [57.3%]) provided 4808 nights of sleep (84.2%) and 3390 days (59.3%) of well-being and cognition assessments. Participants on a float schedule had higher SRI scores (mean [SD] score, 69.4 [6.16]) and had better quality sleep (PSQI mean [SD] score, 5.4 [2.3]), than participants on call schedules (SRI mean [SD] score, 56.1 [11.3]; t91 = 6.81; mean difference, 13.3; 95% CI, 9.40 to 17.22; P < .001; PSQI mean [SD] score, 6.5 [2.3]; t79 = 2.16; 95% CI, 0.09 to 2.15; P = .03). Overnight call shifts, but not night float shifts, were associated with poorer mood (-13%; β = -6.79; 95% CI, -9.32 to -4.27; P < .001), motivation (-21%; β = -10.09; 95% CI, -12.55 to -7.63; P < .001), and sleepiness ratings (29%; β = 15.96; 95% CI, 13.01 to 18.90; P < .001) and impaired vigilance (21 ms slower; β = 20.68; 95% CI, 15.89 to 25.47; P < .001) compared with regular day shifts. Night shifts with naps were associated with better vigilance (16 ms faster; β = -15.72; 95% CI, -28.27 to -3.17; P = .01) than nights without naps.

Conclusions and relevance

In this cohort study, 24-hour call schedules were associated with poorer sleep, well-being, and cognition outcomes than float schedules. Naps during night shifts benefited vigilance in both schedules.

Sleep, Sleep Apnea, and Fatigue in People Living With HIV

BACKGROUND

People living with HIV (PLWH) often report fatigue even when viral load is suppressed. Obstructive sleep apnea (OSA), which is often associated with fatigue, is common in PLWH, but whether OSA explains fatigue in this population is unknown.

SETTING

Academic university-affiliated HIV and Sleep Medicine Clinics.

METHODS

PLWH, aged 18-65 years, with a body mass index of 20-35 kg/m2 and viral suppression (RNA <200 copies per mL), were recruited to undergo daytime questionnaires, including the Functional Assessment of Chronic Illness Therapy Fatigue Scale and Epworth Sleepiness Scale, 7 days of actigraphy (to determine daily sleep duration and activity amplitude and rhythms), and an in-laboratory polysomnography to assess for the presence and severity of OSA.

RESULTS

Of 120 subjects with evaluable data, 90 (75%) had OSA using the American Academy of Sleep Medicine 3% desaturation or arousal criteria, with an apnea-hypopnea index >5/h. There was no difference in Functional Assessment of Chronic Illness Therapy scores between those with and without OSA, although those with OSA did report more daytime sleepiness as measured using the Epworth Sleepiness Scale. In a multivariable model, predictors of fatigue included more variable daily sleep durations and decreased mean activity counts. Sleepiness was predicted by the presence of OSA.

CONCLUSION

OSA was very common in our cohort of PLWH, with those with OSA reporting more sleepiness but not more fatigue. Variability in sleep duration was associated with increased fatigue. Further study is needed to determine if treatment of OSA, or an emphasis on sleep consistency and timing, improves symptoms of fatigue in PLWH.

Association between sleep regularity and arterial stiffness among middle-age adults in Southwestern China

BACKGROUND

Sleep regularity has been linked to a risk of arterial stiffness (AS). However, the association between sleep regularity indicators, which reflect 24-hour sleep variability, and AS has not yet been examined.

METHODS

We analyzed data from 516 adults, aged 40-65 years (the median age of 51 years), from the 'Follow-up Study of Sleep Characteristics and Chronic Diseases in the Middle-aged and Elderly Population in Guizhou Province'. Participants underwent assessments of AS (OMRON HBP-8000, baPWV ≥ 1400 cm/s) and sleep (wrist smart band (Honor band 5i) for ≥ 7 days). Logistic regression was utilized to evaluate the odds ratio (OR) and 95% confidence interval (CI) of the association between sleep regularity and AS.

RESULTS

A total of 516 people were included in this study, of which 279 (54.07%) were in the AS group. The univariate results showed that the AS group (Median 71.18) had lower SRI compared to the No-AS group (Median 75.00) (p < 0.001). The multifactorial results showed participants with higher SRI scores were more likely to have a lower risk of AS compared to those with lower SRI scores (ORQ4 VS. Q1=0.46, 95%CI: 0.25-0.85, p = 0.013). The SRI effect was more pronounced in male (ORQ4 VS. Q1=0.28, 95%CI: 0.12-0.69, p = 0.005), snoring populations (ORQ4 VS. Q1=0.13, 95%CI: 0.04-0.48, p = 0.002), and non-retired populations (ORQ4 VS. Q1=0.45, 95%CI: 0.22-0.92, p = 0.028).

CONCLUSIONS

The present findings indicated that the effect between SRI and AS may be more sensitive than the standard deviation of sleep duration as well as the standard deviation of sleep onset.

Re-Evaluating Recommended Optimal Sleep Duration: A Perspective on Sleep Literacy

A significant number of adolescents experience sleepiness, primarily due to sleep deprivation. The detrimental effects of inadequate sleep on both physical and mental health are well documented, particularly during adolescence-a critical developmental stage that has far-reaching implications for later life outcomes. The International Classification of Diseases 11th Revision recently introduced the disorder termed 'insufficient sleep syndrome,' characterized by a persistent reduction in sleep quantity. However, diagnosing this condition based solely on sleep duration is challenging due to significant individual variation in what constitutes optimal sleep. Despite this, managing sleep debt remains difficult without a clear understanding of individual optimal sleep needs. This review aims to reassess recommended sleep durations, with a focus on enhancing sleep literacy. Beginning with an exploration of insufficient sleep syndrome, this review delves into research on optimal sleep duration and examines foundational studies on sleep debt's impact on the developing brain. Finally, it addresses the challenges inherent in sleep education programs from the perspective of sleep literacy. By doing so, this review seeks to contribute to a deeper understanding of the chronic sleep debt issues faced by adolescents, particularly those affected by insufficient sleep syndrome.

Sleep duration irregularity and risk for incident cardiovascular disease in the UK Biobank

Background

Emerging evidence supports a link between circadian disruption as measured by higher night-to-night variation in sleep duration and increased risk of cardiovascular disease (CVD). It remains unclear whether this association varies by CVD types or may be modified by average sleep duration and genetic risk for CVD.

Methods

Our prospective analysis included 86,219 UK Biobank participants who were free from CVD when completing 7 days of accelerometer measurement in 2013-2016. Sleep irregularity was evaluated by the standard deviation (SD) of accelerometer-measured sleep duration over 7 days. Incident major CVD events, defined as fatal or nonfatal myocardial infarction (MI) and stroke, were identified through linkage to Hospital Episode Statistics data until May 31, 2022. Multivariable-adjusted Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% CIs for associations of sleep duration SD with risk for major CVD events overall and for MI and stroke separately.

Results

We documented 2,310 incident cases of major CVD events (MI: 1,183, stroke: 1,175) over 636,258 person-years of follow-up. After adjusting for sociodemographic factors and family history of CVD, the HR (95% CI) associated with a 1-hour increase in sleep duration SD was 1.19 (1.10, 1.27) for CVD (p-trend<0.0001), 1.23 (1.11, 1.35) for MI (p-trend<0.0001), and 1.17 (1.05, 1.29) for stroke (p-trend=0.003). Additional adjustment for lifestyle factors, co-morbidities and sleep-related factors modestly attenuated these associations. Higher sleep irregularity was associated with higher CVD risk irrespective of genetic risk (p-interaction=0.43), but this association was stronger among individuals with longer average sleep duration >8 hours (p-interaction=0.006).

Conclusions

Higher night-to-night variation in accelerometer-measured sleep duration was associated with consistently higher risks for major CVD events. The association did not seem to be modified by genetic risk for CVD and was more pronounced in long sleepers.

The Bitemporal Lens Model-toward a holistic approach to chronic disease prevention with digital biomarkers

Objectives

We introduce the Bitemporal Lens Model, a comprehensive methodology for chronic disease prevention using digital biomarkers.

Materials and Methods

The Bitemporal Lens Model integrates the change-point model, focusing on critical disease-specific parameters, and the recurrent-pattern model, emphasizing lifestyle and behavioral patterns, for early risk identification.

Results

By incorporating both the change-point and recurrent-pattern models, the Bitemporal Lens Model offers a comprehensive approach to preventive healthcare, enabling a more nuanced understanding of individual health trajectories, demonstrated through its application in cardiovascular disease prevention.

Discussion

We explore the benefits of the Bitemporal Lens Model, highlighting its capacity for personalized risk assessment through the integration of two distinct lenses. We also acknowledge challenges associated with handling intricate data across dual temporal dimensions, maintaining data integrity, and addressing ethical concerns pertaining to privacy and data protection.

Conclusion

The Bitemporal Lens Model presents a novel approach to enhancing preventive healthcare effectiveness.

The Emerging Importance of Sleep Regularity on Cardiovascular Health and Cognitive Impairment in Older Adults: A Review of the Literature

The regularity of sleep/wake patterns across multiple days is emerging as an important determinant of health. However, the association between sleep regularity and health outcomes in the aging population is not well understood. The current systematic review identified 22 publications that examined the relationship between sleep regularity and selected health outcomes: cardiovascular risk, cognitive impairment, and mortality. All studies were published after 2010, reflecting a growing research interest in daily sleep regularity. Low sleep regularity was consistently associated with higher cardiovascular risk and elevated risk of all-cause mortality. Results on cognitive impairment are mixed, with inconsistency likely attributed to small sample sizes and differences in sleep regularity assessment. Overall, regularity in sleep carries important information about health and should be included in future studies that collect daily sleep measures. Gaps in literature and methodological shortcomings are discussed.

Regularity of bedtime, wake-up time, and time in bed in mid-life: associations with cardiometabolic health markers with adjustment for physical activity and sedentary time

BACKGROUND

Insufficient sleep has been linked to the accumulation of cardiometabolic risks while physical activity acts as a protective factor. Also, sleep regularity may play a critical role in maintaining optimal cardiometabolic health. This cross-sectional study examined the association between device-based sleep regularity, waking activity behaviors, and cardiometabolic health markers, including blood pressure level; abdominal adiposity level; and blood glucose, insulin, and cholesterol.

METHODS

We included 3698 members of the Northern Finland Birth cohort 1966 who participated in the follow-up study at the age of 46 years between 2012 and 2014 (women 61%). We used seven-day standard deviations of device-based bedtime, wake-up time, and time in bed to reflect sleep regularities. As covariates in linear regression models, we used commonly known potential risk factors in (gender, education, marital status, work schedule, smoking status, alcohol risk use, seven-day time in bed mean, chronotype). In addition to the previous, we used either sedentary time or total physical activity as a covariate (B coefficients with 95% confidence intervals CI).

RESULTS

When we considered sedentary time with other covariates, irregularities in bedtime, wake-up time, and time in bed were associated with unfavorable cardiometabolic health markers, such as higher body mass index (bedtime regularity: 0.194, 95% CI [0.072, 0.316], p = 0.002); higher diastolic blood pressure levels (time in bed regularity: 0.175, 95% CI [0.044, 0.306], p = 0.009); and higher 2-h glucose levels (wake-up time regularity: 0.107, 95% CI [0.030, 0.184], p = 0.006). When we considered total physical activity with other covariates, only irregular bedtime was associated with higher waist circumference (B 0.199, 95% CI [0.042, 0.356], p = 0.013). Irregularities in bedtime and wake-up time were not associated with higher diastolic blood pressure, higher visceral fat area or higher fasting insulin level after considering sedentary time or total physical activity with other covariates (in all, p > 0.05).

CONCLUSIONS

In middle-aged, physical activity appears to weaken the adverse relationship between irregular sleep and cardiometabolic health markers, although the interpretation of the impact of sedentary time remains less conclusive. The clinical significance and extent of the observed associations warrant further investigation.

Another benefit of regular sleep

A large observational study has found that irregular sleep-wake patterns are associated with a higher risk of overall mortality, and also mortality from cancers and cardiovascular disease.