Temporal relationships between physical activity and sleep in older women

Physical Activity and Cognition: A Mediating Role of Efficient Sleep

OBJECTIVE

Physical activity benefits executive control, but the mechanism through which this benefit occurs is unclear. Sleep is a candidate mechanism given that it improves with exercise and has restorative effects on the prefrontal cortex. The present cross-sectional study examined the mediating role of sleep in the relationship between physical activity and executive control in young and older adults.

PARTICIPANTS

Young (n = 59) and older (n = 53) community-dwelling adults ages 21-30 and 55-80.

METHODS

Participants wore an accelerometer for one week to assess sleep efficiency, total sleep time, and physical activity, operationalized as metabolic equivalent of task (METs) during time spent awake. Cognition was assessed in the laboratory across multiple measures of executive control, memory recall, and processing speed. Mediation analyses tested the role of sleep efficiency in the cross-sectional relationship between METs and cognitive performance accounting for age, sex, and education.

RESULTS

METs were significantly associated with performance before, but not after accounting for covariates. METs were associated with sleep efficiency but not total sleep time. Sleep efficiency, but not total sleep time, mediated the relationship between METs and working memory, switching, verbal ability and fluency, and recall. Age group did not moderate the mediating role of sleep efficiency in the relationship between METs and performance.

CONCLUSION

Sleep efficiency is one pathway by which physical activity may be associated with executive control across young and older adults.

Analysis of dynamic, bidirectional associations in older adult physical activity and sleep quality

Sleep quality and physical activity (PA) appear to be interrelated; thus, by promoting one behaviour, it may be possible to improve the other in older adults. Examination of the within-person day-to-day variation in PA and sleep quality could potentially elucidate the directionality of the association of these behaviours. We measured sleep quality (i.e. fragmentation, efficiency, duration and latency) and moderate-to-vigorous PA using the MotionWatch8© over 14 consecutive days and nights in community-dwelling adults (n = 152; age range 53-101 years). Multilevel modelling estimated within-subject autoregressive and cross-lagged effects and between-subject associations between PA and sleep quality. On days when individuals engaged in a high amount of PA on one day (relative to their averages), they were more likely to engage in a high amount of PA on the next day (estimate, 0.19; 95% CI, 0.14, 0.24). Nights in which individuals had a long sleep latency were followed by nights in which they also had a long sleep latency (estimate, 0.09; 95% CI, 0.03, 0.14). In contrast, nights in which individuals slept for a long period of time were followed by nights in which they slept relatively less than their averages (estimate, -0.09; 95% CI, -0.13, -0.04). When individuals engaged in a large amount of PA during the day, they tended to sleep longer that following night (estimate, 0.01; 95% CI, 0.001, 0.02). All other associations between PA and sleep quality were not significant. Increasing PA therefore might increase sleep duration in older adults.

Efficacy of Exercise Intervention for Weight Loss in Overweight and Obese Adolescents: Meta-Analysis and Implications

BACKGROUND

The global rise in obesity prevalence among children and adolescents has been linked to modifiable lifestyle factors, including lack of physical activity. However, no known meta-analysis has been conducted on the effects of exercise intervention on body composition and cardiometabolic risk factors in overweight and obese adolescents.

OBJECTIVES

The aim of this study was to (1) estimate whether exercise intervention meaningfully improves body composition and cardiometabolic risk factors in overweight and obese adolescents; and (2) discuss the implications of the findings in terms of primary healthcare provision and public health policy, using New Zealand as an exemplar context.

DATA SOURCES

Electronic databases (PubMed, Web of Science, SPORTDiscus, Google Scholar) from inception to May 2015. The reference lists of eligible articles and relevant reviews were also checked.

STUDY SELECTION

Inclusion criteria were (1) randomized controlled trial; (2) structured exercise intervention, alone or combined with any other kind of intervention; (3) control group received no structured exercise or behavioural modification designed to increase physical activity; (4) participants overweight or obese (body mass index [BMI] ≥85th percentile); and (5) participants aged between 10 and 19 years.

APPRAISAL AND SYNTHESIS METHODS

Initially, 1667 articles were identified. After evaluation of study characteristics, quality and validity, data from 13 articles (15 trials) involving 556 participants (176 male, 193 female, 187 unknown) were extracted for meta-analysis. Meta-analyses were completed on five body composition parameters and ten cardiometabolic parameters. Effect sizes (ESs) were calculated as mean differences, as well as standardized mean differences in order to determine effect magnitude.

RESULTS

Exercise intervention reduced BMI (mean 2.0 kg/m², 95 % CI 1.5-2.5; ES moderate), body weight (mean 3.7 kg, 95 % CI 1.7-5.8; ES small), body fat percentage (3.1 %, 95 % CI 2.2-4.1; ES small), waist circumference (3.0 cm, 95 % CI 1.3-4.8; ES small), but the increase (improvement) in lean mass was trivial (mean 1.6 kg, 95 % CI 0.5-2.6). The response to an oral glucose tolerance test following exercise intervention was for a decrease in the area under the curve for insulin (mean 162 μU/μl, 95 % CI 93-231; ES large) and blood glucose (mean 39 mg/dl, 95 % CI 9.4-69; ES moderate). Improvements in the homeostatic model assessment were also noted (mean 1.0, 95 % CI 0.7-1.4; ES moderate) and systolic blood pressure (mean 7.1 mmHg, 95 % CI 3.5-10.7; ES moderate). The effects of exercise on total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, fasting insulin and fasting blood glucose were inconclusive.

LIMITATIONS

Most of the included trials were short term (6-36 weeks) and 13 had methodological limitations. Additionally, the meta-analyses for some of the secondary outcomes had a small number of participants or substantial statistical heterogeneity.

CONCLUSIONS

The current evidence suggests that exercise intervention in overweight and obese adolescents improves body composition, particularly by lowering body fat. The limited available evidence further indicates that exercise intervention may improve some cardiometabolic risk factors.

The Temporal Order of Changes in Physical Activity and Subjective Sleep in Depressed Versus Nondepressed Individuals: Findings From the MOOVD Study

Epidemiological studies have shown an association between physical activity and sleep, but it is unclear what the temporal order of this association is and whether it differs for depressed patients and healthy controls. Using a multiple repeated observations design, 27 depressed and 27 pair-matched nondepressed participants completed daily measurements of subjective sleep quality and duration during 30 consecutive days while an accelerometer continuously registered their physical activity. Changes in sleep duration, not quality, predicted next-day changes in physical activity (B = -0.21, p < .001), but not the other way around. Significant heterogeneity between individuals was observed, but the effect was not different for depressed and nondepressed participants. The findings underline the strength of a multiple repeated observations design in observational sleep research.

Improving Cardiometabolic Health with Diet, Physical Activity, and Breaking Up Sitting: What about Sleep?

Cardiometabolic disease poses a serious health and economic burden worldwide and its prevalence is predicted to increase. Prolonged sitting, lack of physical activity, poor diet, and short sleep duration are ubiquitous behaviors in modern society, and all are independent risk factors in the development of cardiometabolic disease. Existing evidence demonstrates that breaking up prolonged periods of sitting is beneficial for cardiometabolic health, however, studies have not controlled for prior sleep duration. This article examines how prolonged sitting and short sleep duration independently contribute to cardiometabolic risk, and how breaking up sitting and obtaining adequate sleep may reduce this risk. We suggest that as prolonged sitting and short sleep duration influence the same cardiometabolic parameters, there is potential for short sleep to attenuate the positive impact of breaking up prolonged sitting with physical activity. Likewise, breaking up prolonged sitting and obtaining adequate sleep together could improve predictors of cardiometabolic disease, i.e., the combined effect may be stronger than either alone. To explore these perspectives, we propose a research agenda to investigate the relationship between breaking up prolonged sitting with physical activity and short sleep duration. This will provide an evidence-base for informing the design of interventions to reduce the burden of cardiometabolic disease on communities worldwide.

The relations between sleep, time of physical activity, and time outdoors among adult women

Physical activity and time spent outdoors may be important non-pharmacological approaches to improve sleep quality and duration (or sleep patterns) but there is little empirical research evaluating the two simultaneously. The current study assesses the role of physical activity and time outdoors in predicting sleep health by using objective measurement of the three variables. A convenience sample of 360 adult women (mean age = 55.38 ±9.89 years; mean body mass index = 27.74 ±6.12) was recruited from different regions of the U.S. Participants wore a Global Positioning System device and ActiGraph GT3X+ accelerometers on the hip for 7 days and on the wrist for 7 days and 7 nights to assess total time and time of day spent outdoors, total minutes in moderate-to-vigorous physical activity per day, and 4 measures of sleep health, respectively. A generalized mixed-effects model was used to assess temporal associations between moderate-to-vigorous physical activity, outdoor time, and sleep at the daily level (days = 1931) within individuals. There was a significant interaction (p = 0.04) between moderate-to-vigorous physical activity and time spent outdoors in predicting total sleep time but not for predicting sleep efficiency. Increasing time outdoors in the afternoon (versus morning) predicted lower sleep efficiency, but had no effect on total sleep time. Time spent outdoors and the time of day spent outdoors may be important moderators in assessing the relation between physical activity and sleep. More research is needed in larger populations using experimental designs.

Replacing sedentary time with sleep, light, or moderate-to-vigorous physical activity: effects on self-regulation and executive functioning

Recent attention has highlighted the importance of reducing sedentary time for maintaining health and quality of life. However, it is unclear how changing sedentary behavior may influence executive functions and self-regulatory strategy use, which are vital for the long-term maintenance of a health behavior regimen. The purpose of this cross-sectional study is to examine the estimated self-regulatory and executive functioning effects of substituting 30 min of sedentary behavior with 30 min of light activity, moderate-to-vigorous physical activity (MVPA), or sleep in a sample of older adults. This study reports baseline data collected from low-active healthy older adults (N = 247, mean age 65.4 ± 4.6 years) recruited to participate in a 6 month randomized controlled exercise trial examining the effects of various modes of exercise on brain health and function. Each participant completed assessments of physical activity self-regulatory strategy use (i.e., self-monitoring, goal-setting, social support, reinforcement, time management, and relapse prevention) and executive functioning. Physical activity and sedentary behaviors were measured using accelerometers during waking hours for seven consecutive days at each time point. Isotemporal substitution analyses were conducted to examine the effect on self-regulation and executive functioning should an individual substitute sedentary time with light activity, MVPA, or sleep. The substitution of sedentary time with both sleep and MVPA influenced both self-regulatory strategy use and executive functioning. Sleep was associated with greater self-monitoring (B = .23, p = .02), goal-setting (B = .32, p < .01), and social support (B = .18, p = .01) behaviors. Substitution of sedentary time with MVPA was associated with higher accuracy on 2-item (B = .03, p = .01) and 3-item (B = .02, p = .04) spatial working memory tasks, and with faster reaction times on single (B = -23.12, p = .03) and mixed-repeated task-switching blocks (B = -27.06, p = .04). Substitution of sedentary time with sleep was associated with marginally faster reaction time on mixed-repeated task-switching blocks (B = -12.20, p = .07) and faster reaction time on mixed-switch blocks (B = 17.21, p = .05), as well as reduced global reaction time switch cost (B = -16.86, p = .01). Substitution for light intensity physical activity did not produce significant effects. By replacing sedentary time with sleep and MVPA, individuals may bolster several important domains of self-regulatory behavior and executive functioning. This has important implications for the design of long-lasting health behavior interventions. Trial Registration clinicaltrials.gov identifier NCT00438347.

Associations of domain-specific physical activities with insomnia symptoms among 0.5 million Chinese adults

Previous studies have demonstrated the association between physical activity and sleep quality. However, there is little evidence regarding different domains of physical activity. This study aimed to examine the associations between domain‐specific physical activities and insomnia symptoms among Chinese men and women. Data of 452 024 Chinese adults aged 30–79 years from the China Kadoorie Biobank Study were analysed. Insomnia symptoms were assessed with self‐reported difficulties in initiating or maintaining sleep, early morning awakening, daytime dysfunction and any insomnia symptoms. Physical activity assessed by questionnaire consisted of four domains, including occupational, commuting‐related, household and leisure‐time activities. Gender‐specific multiple logistic regression models were employed to estimate independent associations of overall and domain‐specific physical activities with insomnia symptoms. Overall, 12.9% of men and 17.8% of women participants reported having insomnia symptoms. After adjustment for potential confounders, a moderate to high level of overall activity was associated with reduced risks of difficulties in initiating or maintaining sleep and daytime dysfunction in both sexes (odds ratios range: 0.87–0.94, P < 0.05). As to each domain of physical activity, similar associations were identified for occupational, household and leisure‐time activities in women but not men (odds ratios range: 0.84–0.94, P < 0.05). Commuting‐related activity, however, was associated with increased risks of difficulties in initiating or maintaining sleep and any insomnia symptoms in both sexes (odds ratios range: 1.07–1.17, P < 0.05). In conclusion, a moderate to high level of physical activity was associated with lower risks of insomnia symptoms among Chinese adults. However, such associations varied hugely in different domains of physical activity and with gender differences, which could help with better policy‐making and clinical practice.

Bidirectional associations of accelerometer-determined sedentary behavior and physical activity with reported time in bed: Women's Health Study

OBJECTIVE

To examine the day-to-day, bidirectional associations of accelerometer-derived sedentary behavior and physical activity (PA) with reported time in bed in a large cohort of older women.

METHODS

Data are from 10086 Women's Health Study participants (aged 71.6 years; SD, 5.7) who agreed to wear an accelerometer and complete a diary for 7 consecutive days. Generalized linear (multilevel) models with repeated measures were used to examine the adjusted associations of the following: (1) reported time in bed with next-day accelerometer-determined counts and time spent sedentary and in light- and moderate-to-vigorous-intensity PA (MVPA) and (2) accelerometer estimates with reported time in bed that night, expressed as short (<7 hours), optimal (7-9 hours), and long (>9 hours) sleep.

RESULTS

Across days, short sleep was associated with an average of 5500 (SE, 1352) higher accelerometer counts the following day but was also related to higher average sedentary (46.5 [SE, 1.5] minutes) and light-intensity PA (11.9 [SE, 1.2] minutes) than optimal sleep (all P<.001). Long sleep was associated with lower accelerometer counts, time spent sedentary and in light-intensity PA, and a reduced likelihood of engaging in ≥20 minutes of MVPA (all P<.001) than optimal sleep. Higher PA during the day (higher accelerometer counts and ≥20 minutes of accumulated MVPA) was associated with a reduced likelihood of reporting short or long sleep that night (all P<.001).

CONCLUSIONS

Findings support the bidirectional associations of accelerometer-determined sedentary behavior and PA with reported time in bed in older women. Future studies are needed to confirm findings with sleep actigraphy in older women.

Analysis of nocturnal actigraphic sleep measures in patients with COPD and their association with daytime physical activity

BACKGROUND

Sleep disturbances are common in patients with chronic obstructive pulmonary disease (COPD) with a considerable negative impact on their quality of life. However, factors associated with measures of sleep in daily life have not been investigated before nor has the association between sleep and the ability to engage in physical activity on a day-to-day basis been studied.

AIMS

To provide insight into the relationship between actigraphic sleep measures and disease severity, exertional dyspnoea, gender and parts of the week; and to investigate the association between sleep measures and next day physical activity.

METHODS

Data were analysed from 932 patients with COPD (66% male, 66.4±8.3 years, FEV₁% predicted=50.8±20.5). Participants had sleep and physical activity continuously monitored using a multisensor activity monitor for a median of 6 days. Linear mixed effects models were applied to investigate the factors associated with sleep impairment and the association between nocturnal sleep and patients' subsequent daytime physical activity.

RESULTS

Actigraphic estimates of sleep impairment were greater in patients with worse airflow limitation and worse exertional dyspnoea. Patients with better sleep measures (ie, non-fragmented sleep, sleeping bouts ≥225 min, sleep efficiency ≥91% and time spent awake after sleep onset <57 min) spent significantly more time in light (p<0.01) and moderate-to-vigorous physical activity (p<0.01).

CONCLUSIONS

There is a relationship between measures of sleep in patients with COPD and the amount of activity they undertake during the waking day. Identifying groups with specific sleep characteristics may be useful information when designing physical activity-enhancing interventions.

Influence of Day Length and Physical Activity on Sleep Patterns in Older Icelandic Men and Women

STUDY OBJECTIVES

To identify cross-sectional and seasonal patterns of sleep and physical activity (PA) in community-dwelling, older Icelandic adults using accelerometers.

METHODS

A seven-day free-living protocol of 244 (110 female) adults aged 79.7 ± 4.9 years was conducted as part of a larger population-based longitudinal observational-cohort study in the greater Reykjavik area of Iceland. A subpopulation (n = 72) repeated the 7-day measurement during seasonal periods with greater (13.4 ± 1.4 h) and lesser (7.7 ± 1.8 h) daylight.

RESULTS

Cross-sectional analyses using multiple linear regression models revealed that day length was a significant independent predictor of sleep duration, mid-sleep, and rise time (all p < 0.05). However, the actual within-individual differences in sleep patterns of the repeaters were rather subtle between periods of longer and shorter day-lengths. Compared to women, men had a shorter sleep duration (462 ± 80 vs. 487 ± 68 minutes, p = 0.008), earlier rise time, and a greater number of awakenings per night (46.5 ± 18.3 vs. 40.2 ± 15.7, p = 0.007), but sleep efficiency and onset latency were similar between the two sexes. Daily PA was also similar between men and women and between periods of longer and shorter day-lengths. BMI, age, gender, and overall PA all contributed to the variations in sleep parameters using multiple regression analysis.

CONCLUSIONS

The sleep and PA characteristics of this unique population revealed some gender differences, but there was limited variation in response to significant daylight changes which may be due to long-term adaptation.

Longitudinal functional additive model with continuous proportional outcomes for physical activity data

Motivated by physical activity data obtained from the BodyMedia FIT device (www.bodymedia.com), we take a functional data approach for longitudinal studies with continuous proportional outcomes. The functional structure depends on three factors. In our three-factor model, the regression structures are specified as curves measured at various factor-points with random effects that have a correlation structure. The random curve for the continuous factor is summarized using a few important principal components. The difficulties in handling the continuous proportion variables are solved by using a quasilikelihood type approximation. We develop an efficient algorithm to fit the model, which involves the selection of the number of principal components. The method is evaluated empirically by a simulation study. This approach is applied to the BodyMedia data with 935 males and 84 consecutive days of observation, for a total of 78, 540 observations. We show that sleep efficiency increases with increasing physical activity, while its variance decreases at the same time.

No Evidence of Reciprocal Associations between Daily Sleep and Physical Activity

PURPOSE

This study aimed to determine whether physical activity patterns are associated with sleep later at night and if nighttime sleep is associated with physical activity patterns the next day among adult women.

METHODS

Women (N = 353) living throughout the United States wore a wrist and a hip accelerometer for 7 d. Total sleep time (TST, hours per night) and sleep efficiency (SE, %) were estimated from the wrist accelerometer, and moderate to vigorous physical activity (MVPA, >1040 counts per minute, h·d) and sedentary behavior (SB, <100 counts per minute, h·d) were estimated from the hip accelerometer. Mixed-effects models adjusted for age, race, body mass index, education, employment, marital status, health status, and hip accelerometer wear time were used to analyze the data. Follow-up analyses using quantile regression were used to investigate associations among women with below average TST and MVPA and above average SB.

RESULTS

The average age of our sample was 55.5 yr (SD = 10.2 yr). The majority of participants were White (79%) and married (72%), and half were employed full time (49%). The participants spent on average 8.9 and 1.1 h·d in SB and MVPA, respectively, and 6.8 h per night asleep. No associations were observed between MVPA and SB with nighttime TST or SE. There were no associations between nighttime TST and SE with MVPA or SB the next day. The findings were the same in the quantile regression analyses.

CONCLUSION

In free-living adult women, accelerometry-estimated nighttime sleep and physical activity patterns were not associated with one another. On the basis of our observational study involving a sample of adult women, higher physical activity will not necessarily improve sleep at night on a day-to-day basis (and vice versa).

The convergent validity of Actiwatch 2 and ActiGraph Link accelerometers in measuring total sleeping period, wake after sleep onset, and sleep efficiency in free-living condition

PURPOSE

Physical activity (PA) and sleep are important to health; thus, it is important for researchers to have valid tools to measure them. Accelerometers have been proven valid for measuring PA and sleep, but only one device does this simultaneously: the ActiGraph Link (ActiGraph, LLC); however, the sleep-monitoring function has not been validated. This study aimed to evaluate the predictive power of ActiGraph Link sleep parameters against a validated accelerometer (Actiwatch 2, Phillips Respironics Mini-Mitter).

METHODS

A total of 49 Hong Kong adults aged 18-64 provided valid data on both accelerometers on their non-dominant wrist for seven consecutive days. Epochs from both accelerometers were classified as either sleep or awake using seven established algorithms (Cole-Kripke, Sadeh, Sazonov, high sensitivity threshold, medium sensitivity threshold, low sensitivity threshold, and neural network model), and these data were transformed to total sleeping period, wake after sleep onset, and sleep efficiency.

RESULTS

The non-zero count data for both accelerometers (331,103 observations) were strongly correlated with a Spearman correlation of 0.83 (p < 0.001). The total sleeping period was highly correlated (Spearman correlation ranged from 0.74 to 0.90) regardless of the algorithms used. All algorithms yielded insignificant difference in total sleep time measured by the two accelerometers (p > 0.05) with a negligible effect size of d < 0.2. The agreement of sleep/wake status was high for all algorithms, with accuracy ranging from 93.05 % (Sadeh's algorithm) to 96.13 % (Cole-Kripke's algorithm).

CONCLUSIONS

Results showed that the sleep function of the ActiGraph Link performs similar to a validated accelerometer (Actiwatch 2) and provides an opportunity to measure both sleep and PA simultaneously.

Physical Activity, Mind Wandering, Affect, and Sleep: An Ecological Momentary Assessment

BACKGROUND

A considerable portion of daily thought is spent in mind wandering. This behavior has been related to positive (eg, future planning, problem solving) and negative (eg, unhappiness, impaired cognitive performance) outcomes.

OBJECTIVE

Based on previous research suggesting future-oriented (ie, prospective) mind wandering may support autobiographical planning and self-regulation, this study examined associations between hourly mind wandering and moderate-to-vigorous physical activity (MVPA), and the impact of affect and daily sleep on these relations.

METHODS

College-aged adults (N=33) participated in a mobile phone-delivered ecological momentary assessment study for 1 week. Sixteen hourly prompts assessing mind wandering and affect were delivered daily via participants' mobile phones. Perceived sleep quality and duration was assessed during the first prompt each day, and participants wore an ActiGraph accelerometer during waking hours throughout the study week.

RESULTS

Study findings suggest present-moment mind wandering was positively associated with future MVPA (P=.03), and this relationship was moderated by affective state (P=.04). Moreover, excessive sleep the previous evening was related to less MVPA across the following day (P=.007). Further, mind wandering was positively related to activity only among those who did not oversleep (P=.007).

CONCLUSIONS

Together, these results have implications for multiple health behavior interventions targeting physical activity, affect, and sleep. Researchers may also build on this work by studying these relationships in the context of other important behaviors and psychosocial factors (eg, tobacco use, depression, loneliness).

Balanced: a randomised trial examining the efficacy of two self-monitoring methods for an app-based multi-behaviour intervention to improve physical activity, sitting and sleep in adults

BACKGROUND

Many adults are insufficiently physically active, have prolonged sedentary behaviour and report poor sleep. These behaviours can be improved by interventions that include education, goal setting, self-monitoring, and feedback strategies. Few interventions have explicitly targeted these behaviours simultaneously or examined the relative efficacy of different self-monitoring methods.

METHODS/DESIGN

This study aims to compare the efficacy of two self-monitoring methods in an app-based multi-behaviour intervention to improve objectively measured physical activity, sedentary, and sleep behaviours, in a 9 week 2-arm randomised trial. Participants will be adults (n = 64) who report being physically inactive, sitting >8 h/day and frequent insufficient sleep (≥14 days out of last 30). The "Balanced" intervention is delivered via a smartphone 'app', and includes education materials (guidelines, strategies to promote change in behaviour), goal setting, self-monitoring and feedback support. Participants will be randomly allocated to either a device-entered or user-entered self-monitoring method. The device-entered group will be provided with a activity tracker to self-monitor behaviours. The user-entered group will recall and manually record behaviours. Assessments will be conducted at 0, 3, 6, and 9 weeks. Physical activity, sedentary behaviour and sleep-wake behaviours will be measured using the wrist worn Geneactiv accelerometer. Linear mixed models will be used to examine differences between groups and over time using an alpha of 0.01.

DISCUSSION

This study will evaluate an app-based multi-behavioural intervention to improve physical activity, sedentary behaviour and sleep; and the relative efficacy of two different approaches to self-monitoring these behaviours. Outcomes will provide information to inform future interventions and self-monitoring targeting these behaviours.

TRIAL REGISTRATION

ACTRN12615000182594 (Australian New Zealand Clinical Trials Registry. Registry URL: www.anzctr.org.au ; registered prospectively on 25 February 2015).

Genotype vs. Phenotype and the Rise of Non-Communicable Diseases: The Importance of Lifestyle Behaviors During Childhood

Despite continued research and growing public awareness, the incidence of non-communicable diseases (NCD) continues to accelerate. While a person may have a genetic predisposition to certain NCDs, the rapidly changing epidemiology of NCDs points to the importance of environmental, social, and behavioural determinants of health. Specifically, three lifestyle behaviours expose children to important environmental cues and stressors: physical activity, nutritional intake, and sleep behaviour. Failure to expose children to proper gene-environment interactions, through the aforementioned lifestyle behaviours, can and will predispose children to the development of NCDs. Reengineering the environments of children can induce a paradigm shift, from a predominantly biomedical health model of treating symptomology, to a more holistic model based on encouraging appropriate behavioral decisions and optimal health.

Greater bed- and wake-time variability is associated with less healthy lifestyle behaviors: a cross-sectional study

AIM

This study examines associations between the variability in bed/rise times, usual bed/rise time and dietary quality, physical activity, alcohol consumption, sitting time, sleep insufficiency and a composite index of behaviors.

SUBJECT AND METHODS

A random sample of Australian adults drawn from an online Panel cohort in 2013 completed a cross-sectional online survey. A total of 1,317 participants, median age 57 (IQR=20) completed the survey. Bed- and wake times, variability in bed- and wake-times, dietary quality, physical activity, alcohol consumption, sitting time, sleep insufficiency and socio-demographics were assessed using a questionnaire. Associations were examined with generalized linear models.

RESULTS

Having bed - times that varied by >30 min were associated with lower dietary quality, higher alcohol consumption, higher sitting time, more frequent insufficient sleep and poorer overall pattern of lifestyle behaviors. Greater variability in wake times, usual bed times and usual wake times were inconsistently associated with lifestyle behaviours.

CONCLUSIONS

Greater bed-time variability is associated with a less healthy pattern of lifestyle behaviors. Greater consistency in sleep timing may contribute to, or be reflective of, a healthier lifestyle.

Decline in cardiorespiratory fitness and odds of incident sleep complaints

PURPOSE

To examine longitudinal change in cardiorespiratory fitness and odds of incident sleep problems.

METHODS

A cohort of 7368 men and 1155 women, age 20-85 yr, was recruited from the Aerobics Center Longitudinal Study. The cohort did not complain of sleep problems, depression, or anxiety at their first clinic visit. Cardiorespiratory fitness assessed at four clinic visits between 1971 and 2006, each separated by an average of 2-3 yr, was used as a proxy measure of cumulative physical activity exposure. Sleep complaints were made to a physician during follow-up.

RESULTS

Across visits, there were 784 incident cases of sleep complaints in men and 207 cases in women. After adjusting for age, time between visits, body mass index, smoking, alcohol use, chronic medical conditions, complaints of depression or anxiety at each visit, and fitness at visit 1, each minute of decline in treadmill endurance (i.e., a decline in cardiorespiratory fitness of approximately 0.5 MET) between the ages of 51 and 56 yr increased the odds of incident sleep complaints by 1.7% (range = 1.0%-2.4%) in men and by 1.3% (range = 0.0%-2.8%) in women. Odds were ∼8% higher per minute decline in people with sleep complaints at visits 2 and 3.

CONCLUSIONS

The results indicate that maintenance of cardiorespiratory fitness during middle age, when decline in fitness typically accelerates and risk of sleep problems is elevated, helps protect against the onset of sleep complaints made to a physician.

Sedentary behavior and sleep efficiency in active community-dwelling older adults

OBJECTIVES

Previous studies have demonstrated that aerobic exercise interventions have a positive impact on sleep efficiency in older adults. However, little work has been done on the impact of sedentary behavior (sitting, watching television, etc.) on sleep efficiency.

METHODS

54 Community-dwelling men and women >65 years of age living in Whistler, British Columbia (mean 71.5 years) were enrolled in this cross-sectional observational study. Measures of sleep efficiency as well as average waking sedentary (ST), light (LT), and moderate (MT) activity were recorded with Sensewear accelerometers worn continuously for 7 days.

RESULTS

From the univariate regression analysis, there was no association between sleep efficiency and the predictors LT and MT. There was a small negative association between ST and sleep efficiency that remained significant in our multivariate regression model containing alcohol consumption, age and gender as covariates. (standardized β correlation coefficient -0.322, p=0.019). Although significant, this effect was small (an increase in sedentary time of 3 hours per day was associated with an approximately 5% reduction in sleep efficiency).

CONCLUSIONS

This study found a small significant association between the time spent sedentary and sleep efficiency, despite high levels of activity in this older adult group.

Associations between physical activity, sedentary time, sleep duration and daytime sleepiness in US adults

OBJECTIVE

To examine the associations between objectively measured physical activity (PA) or sedentary behavior and self-reported sleep duration or daytime sleepiness in a nationally representative sample of healthy US adults (N=2128).

METHODS

We report analyses of four aspects of sedentary behavior and PA derived from accelerometry data (minutes of sedentary time, activity counts/minute, Minutes of Moderate and Vigorous PA [MVPA], and MVPA in 10-minute bouts) versus self-report of sleep duration and frequency of daytime sleepiness from the 2005-2006 National Health and Nutrition Examination Survey.

RESULTS

Age and sex dependence of associations between PA and sleep were observed. Aspects of PA were significantly lower in adults reporting more frequent daytime sleepiness in younger (20-39) and older (≥ 60) age groups, but not in middle-aged (40-59), respondents. In younger respondents, PA increased with sleep duration, but in middle aged and older respondents PA was either unrelated to sleep duration or lower in those reporting ≥ 8 h of sleep. Objectively measured sedentary time showed limited evidence of associations with sleep duration.

CONCLUSIONS

Further research delineating the relationships between sleep and PA is important because both activities have been implicated in diverse health outcomes as well as in the etiology of obesity.

The bidirectional relationship between exercise and sleep: Implications for exercise adherence and sleep improvement

Exercise has long been associated with better sleep, and evidence is accumulating on the efficacy of exercise as a nonpharmacologic treatment option for disturbed sleep. Recent research, however, has noted that poor sleep may contribute to low physical activity levels, emphasizing a robust bidirectional relationship between exercise and sleep. This article will briefly review the evidence supporting the use of exercise as a nonpharmacologic treatment for sleep disturbance, outline future research that is needed to establish the viability of exercise as a behavioral sleep treatment, describe recent research that has emphasized the potential influence of poor sleep on daytime activity levels, and discuss whether improving sleep may facilitate adoption and/or better adherence to a physically active lifestyle. With poor sleep and physical inactivity each recognized as key public health priorities, additional research into the bidirectional relationship between exercise and sleep has significant implications for facilitating greater exercise adherence and improving sleep in society.

Exercise and sleep in aging: emphasis on serotonin

Reductions in central serotonin activity with aging might be involved in sleep-related disorders in later life. Although the beneficial effects of aerobic exercise on sleep are not new, sleep represents a complex recurring state of unconsciousness involving many lines of transmitters which remains only partly clear despite intense ongoing research. It is known that serotonin released into diencephalon and cerebrum might play a key inhibitory role to help promote sleep, likely through an active inhibition of supraspinal neural networks. Several lines of evidence support the stimulatory effects of exercise on higher serotonergic pathways. Hence, exercise has proved to elicit acute elevations in forebrain serotonin concentrations, an effect that waned upon cessation of exercise. While adequate exercise training might lead to adaptations in higher serotonergic networks (desensitization of forebrain receptors), excessive training has been linked to serious brain serotonergic maladaptations accompanied by insomnia. Dietary supplementation of tryptophan (the only serotonin precursor) is known to stimulate serotonergic activity and promote sleep, whereas acute tryptophan depletion causes deleterious effects on sleep. Regarding sleep-wake regulation, exercise has proved to accelerate resynchronization of the biological clock to new light-dark cycles following imposition of phase shifts in laboratory animals. Noteworthy, the effect of increased serotonergic transmission on wake state appears to be biphasic, i.e. promote wake and thereafter drowsiness. Therefore, it might be possible that acute aerobic exercise would act on sleep by increasing activity of ascending brain serotonergic projections, though additional work is warranted to better understand the implication of serotonin in the exercise-sleep axis.

Sleep in older adults: normative changes, sleep disorders, and treatment options

Approximately 5% of older adults meet criteria for clinically significant insomnia disorders and 20% for sleep apnea syndromes. It is important to distinguish age-appropriate changes in sleep from clinically significant insomnia, with the latter having associated daytime impairments. Non-pharmacologic therapies, such as cognitive-behavioral therapy for insomnia, can be highly effective with sustained benefit. Pharmacologic therapies are also available, but may be associated with psychomotor effects. A high index of suspicion is crucial for effective diagnosis of sleep apnea because symptoms commonly noted in younger patients, such as obesity or loud snoring, may not be present in older patients.

Daytime sleepiness and risk of coronary heart disease and stroke: results from the Nurses' Health Study II

OBJECTIVE

The objective of this study was to determine whether daytime sleepiness is independently associated with coronary heart disease (CHD) and stroke or whether the positive association is explained by short sleep duration, disturbed sleep, and circadian disruption, conditions that are associated with cardiometabolic risk factors for vascular events.

METHODS

Longitudinal analyses of data from the Nurses' Health Study II comprising 84,003 female registered nurses aged 37-54 at baseline were conducted in 2001 with follow-up until 2009. Multivariate Cox regression was used to explore the relationship between reported daytime sleepiness and the incidence of either CHD or stroke (n=500 cases).

RESULTS

Women who reported daytime sleepiness almost every day, compared with rarely/never, had an elevated adjusted risk of cardiovascular disease (CVD) (hazard ratio (HR)=1.58, 95% confidence interval (CI) 1.15-2.17). Controlling for sleep variables (sleep duration, snoring, shift work, and sleep adequacy) or potential metabolic biological mediators of disrupted sleep (diabetes, hypercholesterolemia, and hypertension) appreciably attenuated the relationship (HR=1.17, 95% CI 0.84-1.65; and HR=1.34, 95% CI 0.97-1.85, respectively). Controlling for both sleep variables and metabolic risk factors eliminated an independent association (HR=1.09, 95% CI 0.77-1.53). A similar pattern was observed for CHD and stroke individually.

CONCLUSIONS

Daytime sleepiness was not an independent risk factor for CVD in this cohort of women, but rather, was associated with sleep characteristics and metabolic abnormalities that are risk factors for CVD.