Sleep trajectories and mediators of poor sleep: findings from the longitudinal analysis of 41,094 participants of the UK Biobank cohort

Associations between sleep duration trajectories and risk of cardio-metabolic disease among middle-aged and older Chinese adults

BACKGROUND

The association of a single time-point measure of sleep duration with cardio-metabolic disease has been extensively studied, but few studies have focused on the impact of sleep duration trajectory. This study aims to model the sleep duration trajectory as predictors for the subsequent development of cardio-metabolic disease.

METHODS

This study recruited a notably large population (n = 9883) of subjects aged at least 45 years from the China Health and Retirement Longitudinal Study (CHARLS), who participated in sequential surveys conducted in 2011, 2013, 2015, and 2018. Sleep duration trajectories were plotted using data of night sleep duration recorded at intervals from 2011 to 2015 by latent class trajectory model. The onset of cardio-metabolic diseases from 2015 to 2018 were confirmed and then the risk of different sleep duration trajectories on incident cardio-metabolic disease was examined using cox proportional hazards regression model.

RESULTS

We identified four sleep duration trajectories. Compared to the normal-stable trajectory, the short-stable trajectory was significantly associated with higher risk of incident stroke (hazard ratio [HR], 1.32; 95 % confidence interval [CI], 1.02 to 1.70), dyslipidemia (HR, 1.22; 95%CI, 1.01 to 1.49), and diabetes (HR, 1.42; 95%CI, 1.13 to 1.78) within three years of follow-up, and the short-increasing trajectory predicted a higher risk of incident stroke (HR, 2.38; 95%CI, 1.25 to 4.55).

CONCLUSIONS

Short sleep trajectory could increase the risk of incident stroke, dyslipidemia, and diabetes, and an increasing sleep trajectory was associated with increased risk of incident stroke among middle-aged and older Chinese adults.

Associations of objective sleep duration and physical activity with risk of heart failure: A prospective cohort study

OBJECTIVE

This study aimed to investigate the independent and joint associations of accelerometer-derived sleep duration and physical activity (PA) in different intensities with the risk of incident heart failure (HF).

METHODS

The study included 89,572 participants (mean age 62.2 ± 7.8 years, 42.8% male) from the UK Biobank. Sleep duration (short: <6 h/day; normal: 6-8 h/day; long: >8 h/day) and PA [total PA, light PA (LPA), moderate-to-vigorous PA (MVPA), vigorous PA (VPA)] were measured using accelerometers over 7 days. MVPA and VPA were categorized according to the World Health Organization's recommended levels, while LPA and total PA were categorized based on the median. HF cases were identified through hospital records or death registries.

RESULTS

Over a 7-year follow-up period, 1324 participants (2.1%; incidence rate, 2.1 per 1000 person-years) developed HF. Short, but not long, sleep duration was linked to a 33% increased risk of HF [hazard ratio (HR) 1.33, 95% confidence interval (CI): 1.11-1.59]. This increased risk associated with short sleep could be mitigated by increasing PA, especially to the levels of recommended MVPA or VPA. In joint analyses, compared to participants meeting the recommended MVPA and with normal sleep duration, those not meeting the MVPA recommendation and with short sleep had the highest HF risk (HR 1.78, 95% CI: 1.42-2.25).

CONCLUSIONS

Accelerometer-derived short, but not long, sleep duration was associated with a higher risk of incident HF. Engaging in sufficient PA, especially recommended MVPA or VPA, can partially mitigate this risk.

Association between longitudinal change of sleep patterns and the risk of cardiovascular diseases

STUDY OBJECTIVES

To investigate the role of longitudinal change of sleep patterns in the incidence of cardiovascular diseases (CVD).

METHODS

Based on UK Biobank, a total of 18 172 participants were enrolled. Five dimensions of healthy sleep including early chronotype, sleep 7-8 hours/day, free of insomnia, no snoring, and no frequent excessive daytime sleepiness were used to generate a healthy sleep score (HSS) ranging from 0 to 5. Corresponding to the HSS of 0-1, 2-3, and 4-5, the poor, intermediate, and healthy sleep patterns were defined. Based on changes in HSS across assessments 1 and 2, we calculated the absolute difference of HSS. For the change in sleep patterns, we categorized five profiles (stable healthy, worsening, stable intermediate, optimizing, and stable poor sleep patterns). The outcomes were incidence of CVD including coronary heart disease (CHD) and stroke. We assessed the adjusted hazard ratios and 95% confidence intervals (CIs) by Cox hazard models.

RESULTS

Compared with participants with stable poor patterns, those who improved their sleep patterns or maintained healthy sleep patterns had a 26% and 32% lower risk of CVD, respectively. Stable healthy sleep pattern was associated with a 29% and 44% reduced risk of CHD and stroke. Per unit, longitudinal increment of the HSS was related to an 8% lower risk of CVD and CHD. Compared with individuals with constant HSS, those with decreased HSS had a 13% higher risk of developing CVD.

CONCLUSIONS

Optimizing sleep patterns and maintaining a healthy sleep pattern may reduce the risk of CVD.

Parents' Sleep Multi-Trajectory Modelling from 3 to 36 Months Postpartum in the SEPAGES Cohort

Objective

We investigated maternal and paternal sleep evolution from 3 to 36 months postpartum, their interrelations and predictors in the SEPAGES cohort.

Methods

Sleep information (night sleep duration [NSD], weekend daytime sleep duration [DSD] and subjective sleep loss [SSL]) was collected by self-administered questionnaires at 3, 18, 24 and 36 months postpartum in the SEPAGES French cohort that included 484 mothers and 410 fathers. Group-based multi-trajectory modelling was used to identify maternal, paternal and couple sleep multi-trajectory groups among 188 couples reporting sleep data for at least 2 time points. Multinomial logistic regression was used to assess associations between parental sleep multi-trajectories and early characteristics such as sociodemographic, chronotypes, child sex, birth seasonality or breastfeeding duration.

Results

We identified three maternal (M1-M3), paternal (F1-F3) and couple (C1-C3) sleep multi-trajectory groups with similar characteristics: a group with short NSD and high SSL prevalence (M1, F2, C2), a group with long NSD but medium SSL prevalence (M2, F3, C3) and a group with long NSD and low SSL prevalence (M3, F1, C1). Mothers with the shortest NSD (M1) were less likely to have a partner with long NSD (F2). As compared with long NSD and low SSL prevalence (C1), couples with short NSD and high SSL prevalence (C2) were less likely to have had a first child born in the autumn and fathers in C2 had a later chronotype.

Conclusion

We identified distinct sleep multi-trajectory groups for mothers, fathers and couples from 3- to 36-month postpartum. Sleep patterns within couples were homogeneous.

Association of accelerometer-measured sleep duration and different intensities of physical activity with incident type 2 diabetes in a population-based cohort study

PURPOSE

The aim of the current study was to investigate the association of accelerometer-measured sleep duration and different intensities of physical activity (PA) with the risk of incident type 2 diabetes in a population-based prospective cohort study.

METHODS

Altogether, 88,000 participants (mean age = 62.2 ± 7.9 years, mean ± SD) were included from the UK Biobank. Sleep duration (short: <6 h/day; normal: 6-8 h/day; long: >8 h/day) and PA of different intensities were measured using a wrist-worn accelerometer over a 7-day period between 2013 and 2015. PA was classified according to the median or World Health Organization-recommendation: total volume of PA (high, low), moderate-to-vigorous PA (MVPA) (recommended, not recommended), and light-intensity PA (high, low). Incidence of type 2 diabetes was ascertained using hospital records or death registries.

RESULTS

During a median follow-up of 7.0 years, 1615 incident type 2 diabetes cases were documented. Compared with normal sleep duration, short (hazard ratio (HR) = 1.21, 95% confidence interval (95%CI): 1.03-1.41) but not long sleep duration (HR = 1.01, 95%CI: 0.89-1.15) was associated with excessive type 2 diabetes risk. This increased risk among short sleepers seems to be protected against by PA. Compared with normal sleepers with high or recommended PA, short sleepers with low volume of PA (HR = 1.81, 95%CI: 1.46-2.25), not recommended (below the World Health Organization-recommended level of) MVPA (HR = 1.92, 95%CI: 1.55-2.36), or low light-intensity PA (HR = 1.49, 95%CI: 1.13-1.90) had a higher risk of type 2 diabetes, while short sleepers with a high volume of PA (HR = 1.14, 95%CI: 0.88-1.49), recommended MVPA (HR = 1.02, 95%CI: 0.71-1.48), or high light-intensity PA (HR = 1.14, 95%CI: 0.92-1.41) did not.

CONCLUSION

Accelerometer-measured short but not long sleep duration was associated with a higher risk of incident type 2 diabetes. A higher level of PA, regardless of intensity, potentially ameliorates this excessive risk.

The association between proportion of night shifts and musculoskeletal pain and headaches in nurses: a cross-sectional study

BACKGROUND AND PURPOSE

Shift work is associated with musculoskeletal pain and headaches, but little is known about how the intensity of shift work exposure is related to musculoskeletal pain and headaches. This study aimed to investigate whether a higher proportion of night shifts is associated with a higher occurrence of musculoskeletal pain and headaches. Furthermore, to investigate whether sleep duration can mediate this potential association.

METHOD

The study included 684 nurses in rotating shift work who responded to a daily questionnaire about working hours, sleep, and pain for 28 consecutive days. The data were treated cross-sectionally.

RESULTS

A negative binomial regression analysis adjusted for age and BMI revealed that working a higher proportion of night shifts is not associated with a higher occurrence of musculoskeletal pain and headaches. On the contrary, those working ≥ 50% night shifts had a significantly lower occurrence of pain in the lower extremities than those who worked < 25% night shifts (IRR 0.69 95% CI 0.51, 0.94). There was no indication of a mediation effect with total sleep time (TST).

CONCLUSION

The results of this study indicate that working a higher proportion of night shifts is not associated with a higher occurrence of musculoskeletal pain and headaches.

The Impact of Weighted Blanket Use on Adults with Sensory Sensitivity and Insomnia

Purpose

This study's purpose was to determine the impact of weighted blanket use on moderate to severe insomnia in adults with sensory sensitivity greater than the average population.

Methods

For this study, a four-week, single-case, multiple-participant ABA study design was used. Through convenience sampling, four participants scoring 15 or greater on the Insomnia Severity Index (ISI), which categorizes them as having moderate to severe insomnia, and much more than most people in sensory sensitivity on the Adolescent/Adult Sensory Profile were recruited. First, seven-day baseline sleep data was gathered, followed by two weeks of weighted blanket use, concluding with a seven-day withdrawal phase. Additional outcome measures included: Tuck and Snooze Survey, Consensus Sleep Diary Morning, and Additional Sleep Diary Questions. Data analysis included visual analysis, mean comparisons, Tau-U calculations, and pre- to post-ISI category comparisons.

Results

All participants' ISI scores were categorized as one level less severe postintervention. All participants demonstrated increased sleep quality, and three participants showed an increase in sleep duration based on individual mean comparisons between baseline and intervention phases.

Conclusion

Weighted blankets appear beneficial in reducing insomnia severity in adults with much more than the average population sensory sensitivity. In addition, those with self-reported anxiety may have increased benefit from this intervention.

Combined Use of Sleep Quality and Duration Is More Closely Associated With Mortality Risk Among Older Adults: A Population-based Kyoto-Kameoka Prospective Cohort Study

BACKGROUND

Whether sleep quality and duration assessed from multiple domains, either individually or in combination, are strongly associated with mortality risk in older adults remains unelucidated. We aimed to clarify these relationships.

METHODS

We enrolled 7,668 older (age ≥65 years) Japanese adults in the Kyoto-Kameoka prospective cohort study who provided valid responses to the Pittsburgh Sleep Quality Index (PSQI) in a mail-in survey. Sleep quality and duration were classified into six groups using the previously validated PSQI: short sleep duration (SSD: <360 min/day)/sleep disturbance (SD: ≥5.5 PSQI points), n = 701; SSD/non-sleep disturbance (NSD: <5.5 PSQI points), n = 100; optimal sleep duration (OSD: 360-480 min/day)/NSD, n = 1,863; OSD/SD, n = 2,113; long sleep duration (LSD: >480 min/day)/NSD, n = 1,972; LSD/SD, n = 919. Mortality data were collected from February 15, 2012, to November 30, 2016. We evaluated the relationship between all-cause mortality risk and sleep quality and duration (and their combinations) using a multivariable Cox proportional hazards model that included baseline covariates.

RESULTS

The median follow-up period was 4.75 years (34,826 person-years), with a total of 616 deaths. After adjusting for confounders, compared with other groups, SSD/SD and LSD/SD had the highest hazard ratio (HR) of mortality (SSD/SD: HR 1.56; 95% confidence interval [CI], 1.10-2.19; SSD/NSD: HR 1.27; 95% CI, 0.47-3.48; OSD/NSD: reference; OSD/SD: HR 1.20; 95% CI, 0.91-1.59; LSD/NSD: HR 1.35; 95% CI, 1.03-1.77; LSD/SD: HR 1.83; 95% CI, 1.37-2.45). However, mortality risk was not associated with the interaction between sleep quality and duration.

CONCLUSION

Older adults with sleep disturbances involving SSD and LSD have a strong positive association with mortality risk, suggesting an additive effect between sleep quality and duration.

Association between sleep change patterns and mental health among preschoolers: The mediating role of resilience

Sleep disturbance has been recognized as an important factor influencing mental health problems in preschool children. However, no longitudinal studies have investigated the association between sleep change patterns and mental health in preschoolers or the mediating role of resilience. Here, data were collected from 1595 preschool children in 26 kindergartens in four counties in Anhui Province, China, who were followed up (T2) 1 year apart based on baseline surveys (T1). The primary caregivers of the children were asked to complete a structured questionnaire through face-to-face interviews or by completing it themselves. Pearson's correlation and linear regression were used to analyze the relationships among sleep patterns, mental health, and resilience in preschoolers. A structural equation model was used for the mediation analysis. Four patterns of sleep change were identified: persistent-low pattern (1.7%), decreasing pattern (9.8%), increasing pattern (7.3%), and persistent-high pattern (81.3%). Compared to the persistent-low pattern, the increasing pattern and persistent-high pattern were associated with emotional behavioral problems (EBPs) and anxiety. Resilience played a fully mediating role in the relationship between increasing pattern, persistent-high pattern, and EBPs. Resilience partially mediated the effects of increasing and persistent-high pattern on anxiety. More attention should be paid to sleep problems in children with increasing and persistent-high sleep patterns. Resilience is important for understanding the mechanism underlying the correlation between sleep patterns, EBPs, and anxiety. Considering the EBPs and anxiety of preschool children, early intervention for resilience should be considered.

Subjective and objective sleep and circadian parameters as predictors of depression-related outcomes: A machine learning approach in UK Biobank

BACKGROUND

Sleep and circadian disruption are associated with depression onset and severity, but it is unclear which features (e.g., sleep duration, chronotype) are important and whether they can identify individuals showing poorer outcomes.

METHODS

Within a subset of the UK Biobank with actigraphy and mental health data (n = 64,353), penalised regression identified the most useful of 51 sleep/rest-activity predictors of depression-related outcomes; including case-control (Major Depression (MD) vs. controls; postnatal depression vs. controls) and within-case comparisons (severe vs. moderate MD; early vs. later onset, atypical vs. typical symptoms; comorbid anxiety; suicidality). Best models (of lasso, ridge, and elastic net) were selected based on Area Under the Curve (AUC).

RESULTS

For MD vs. controls (n_(MD) = 24,229; n_(control) = 40,124), lasso AUC was 0.68, 95 % confidence interval (CI) 0.67-0.69. Discrimination was reasonable for atypical vs. typical symptoms (n_(atypical) = 958; n_(typical) = 18,722; ridge: AUC 0.74, 95 % CI 0.71-0.77) but poor for remaining models (AUCs 0.59-0.67). Key predictors across most models included: difficulty getting up, insomnia symptoms, snoring, actigraphy-measured daytime inactivity and lower morning activity (~8 am). In a distinct subset (n = 310,718), the number of these factors shown was associated with all depression outcomes.

LIMITATIONS

Analyses were cross-sectional and in middle-/older aged adults: comparison with longitudinal investigations and younger cohorts is necessary.

DISCUSSION

Sleep and circadian measures alone provided poor to moderate discrimination of depression outcomes, but several characteristics were identified that may be clinically useful. Future work should assess these features alongside broader sociodemographic, lifestyle and genetic features.

Short sleep and social jetlag are associated with higher intakes of non-milk extrinsic sugars, and social jetlag is associated with lower fibre intakes in those with adequate sleep duration: a cross-sectional analysis from the National Diet and Nutrition Survey Rolling Programme (Years 1-9)

OBJECTIVE

To investigate associations and interactions between sleep duration and social jetlag status with nutrient intake, nutrient status, body composition and cardio-metabolic risk factors in a nationally representative UK adult population.

DESIGN

A cross-sectional study using 4-d food diary and self-reported sleep data from the UK National Diet and Nutrition Survey Rolling Programme 2008-2017.

SETTING

UK free-living population.

SUBJECTS

Totally, 5015 adults aged 19-64 years.

RESULTS

Thirty-four per cent were short sleepers (< 7 h); 7 % slept ≥ 9 h; 14 % had > 2 h difference in average sleep duration between weeknights and weekend nights (social jetlag). Compared to those reporting optimal sleep duration (≥ 7-< 9 h), short sleep was associated with higher intakes of non-milk extrinsic sugars (NMES) (0·9 % energy, 95 % CI: 0·4, 1·4), total carbohydrate (0·8 % energy, 95 % CI: 0·2, 1·4) and a lower non-starch polysaccharides fibre intake (-0·5 g/d, 95 % CI -0·8, -0·2). There was a significant interaction between short sleep and social jetlag for fibre intakes, where adequate sleepers with social jetlag as well as all short sleepers (regardless of social jetlag) had lower fibre intakes than adequate sleepers with no social jetlag. Short sleep, but not social jetlag, was associated with greater adiposity, but there were no differences in other markers of cardiometabolic disease risk.

CONCLUSIONS

The present study reports that both short sleep and social jetlag are associated with higher intakes of NMES, but only sleep duration is associated with markers of adiposity. Social jetlag was associated with lower fibre intakes even in individuals with adequate weekly sleep duration, suggesting catch-up sleep does not prevent the adverse impact of irregular sleep habits on food choices.

The contribution of daytime sleepiness to impaired quality of life in NAFLD in an ethnically diverse population

Health-related quality of life (HRQoL) is lower in people with NAFLD compared to the general population. Sleep disturbance resulting in daytime sleepiness is common in patients with NAFLD, but the effect of daytime sleepiness on HRQoL in NAFLD is unclear. The prevalence and natural history of NAFLD vary in different ethnic groups, but there has been limited ethnic diversity in HrQoL studies to date. We aimed to assess whether daytime sleepiness is independently associated with reduced HRQoL in an ethnically diverse UK population. We conducted HRQoL assessments using SF-36 version 2 and Epworth Sleepiness Scale (ESS) questionnaires in 192 people with NAFLD. Multivariate linear regression was used to identify factors independently affecting HRQoL scales. People with NAFLD reported significantly reduced physical health-related SF-36 scores compared to the general UK population. South Asian NAFLD patients reported impairment in physical health, but not mental health, approximately a decade before White NAFLD patients. In multivariate linear regression, daytime sleepiness (ESS score > 10), was the most significant independent predictor of reduced physical health. Age, BMI and liver stiffness score were also significantly associated. HRQoL is impaired earlier in patients of South Asian ethnicity. ESS score > 10, indicative of excessive daytime sleepiness, is an independent predictor of reduced HRQoL in people with NAFLD regardless of ethnicity. Daytime sleepiness should be considered as a contributing factor to reduced HRQoL in clinical practice and when evaluating patient-related outcomes in clinical trials.

Emotional Regulation Activities Moderates the Risk of Depression in People With Sleep Disturbance: Evidence From a Community Health Survey

Background and Objective It is widely known that poor sleep quality is closely related to depression, but there are limited studies on the mediating factors.Methods Based on national health survey data, the relationship between sleep quality and depressive symptoms was explored, and structural equations were drawn to determine whether emotional regulation activities, such as regular breakfast, regular exercise, smoking, and drinking contribute to poor sleep quality-induced depression.Results There was a significant correlation between poor sleep quality and depressive symptoms. Regular breakfast tended to mediate between poor sleep quality and depression the most, followed by smoking, drinking, and regular exercise.Conclusions Several emotional regulation activities including regular breakfast, can play a protective role in the process leading to poor sleep quality-induced depression. A follow-up study is required to examine the clinical aspect of how regular breakfast can prevent the process of poor sleep quality to depression.

Understanding the Impact of the COVID-19 Pandemic, Lockdowns and Social Isolation on Sleep Quality

The uncertain, ever-changing and an ongoing nature of the COVID-19 pandemic means that it may take some time before we can fully appreciate the negative effect of the pandemic and lockdown on our sleep and mental health. It is increasingly recognised that in the aftermath of pandemic, several persistent sleep, neuropsychiatric and physical sequelae may continue long after the pandemic is over. A body of evidence to date also highlights a significant disparity in sleep and mental health difficulties in specific vulnerable groups in the community, with different temporal profiles and sleep issues that are reported. In this perspective, we argue for a possible mechanistic impact of the COVID-19 pandemic, with its imposed restrictions and social isolation on sleep quality. We similarly discuss some of the potential international differences, as well as similarities, behind reported idiosyncratic biological vulnerabilities that may have contributed to the genesis of sleep issues. Lastly, we propose some possible implementations and innovations that may be needed in restructuring of sleep disorders services in order to benefit recovering COVID-19 patients.

The Role of Patient-Reported Outcomes in Sleep Measurements

Several questionnaires aka patient-reported outcome measures (PROMs) have been developed for specific use in sleep medicine. Some PROMS are "disease-specific," that is, related to a specific sleep disorder, whereas others are generic. These PROMS constitute a valuable add-on to the conventional history taking. They can be used in the areas of research, clinical practice, and quality of health care appraisal. Still, these instruments have inherent limitations, requiring proficient application in the various areas of interest. Disease-specificity includes a risk for nosologic bias that may confound diagnostic and therapeutic results. Future research should provide solutions for shortcomings of presently available questionnaires.

Association of changes in lifestyle with changes in sleep difficulties: an analysis of 38 400 participants over a 16-year follow-up

OBJECTIVES

To investigate the association between changes in lifestyle risk factors and changes is sleep difficulties.

DESIGN

Longitudinal repeated measures cohort study.

SETTING

University and national institute of occupational health.

PARTICIPANTS

Participants of the Finnish Public Sector study with information on sleep and lifestyle-related risk factors collected in five repeat surveys with 4-year intervals from 2000 to 2017. The participants were those, who had responded at least twice and had a change in sleep difficulties (having sleep difficulties vs not) (142 969 observations from 38 400 respondents (mean age 45.5 (SD 9.2) years, 83% women).

PRIMARY AND SECONDARY OUTCOME MEASURES

Changes in sleep quality over time. Longitudinal fixed effects analysis, a method that accounts for time-invariant confounders by design, was used.

RESULTS

At first available response, sleep difficulties were experienced by 13 998 (36%) of the respondents. Respectively, the mean age was 44.3 (10.0) years, 7526 (20%) were obese, 13 487 (35%) reported low physical activity, 3338 (9%) extensively drinking and 6547 (17%) were smoking. Except for smoking, the changes in the studied modifiable risks were associated with changes in sleep difficulties. The ORs for having sleep difficulties were 1.41 (95% CI 1.35 to 1.48) for obesity, 1.10 (95% CI 1.06 to 1.13) for low physical activity and 1.43 (95% CI 1.35 to 1.51) for heavy drinking. For smoking, the association was negative with OR 0.81 (95% CI 0.76 to 0.86). Including all four modifiable risks into model changed the estimates only little.

CONCLUSIONS

The results of this longitudinal study suggest that changes in sleep quality are interconnected with changes in lifestyle.

Exploration of Sleep as a Specific Risk Factor for Poor Metabolic and Mental Health: A UK Biobank Study of 84,404 Participants

PURPOSE

Short and long sleep durations have adverse effects on physical and mental health. However, most studies are based on self-reported sleep duration and health status. Therefore, this longitudinal study aims to investigate objectively measured sleep duration and subsequent primary health care records in older adults to investigate the impact of sleep duration and fragmentation on physical and mental health.

METHODS

Data on objective sleep duration were measured using accelerometry. Primary care health records were then obtained from the UK Biobank (n=84,404). Participants (mean age, 62.4 years) were divided into five groups according to their sleep duration derived from the accelerometry data: <5 hours, 5-6 hours, 6-7 hours, 7-8 hours and >8 hours. ICD-10 codes were used for the analysis of primary care data. Wake after sleep onset, activity level during the least active 5 hours and episodes of movement during sleep were analysed as an indication for sleep fragmentation. Binary regression models were adjusted for age, gender and Townsend deprivation score.

RESULTS

A "U-shaped" relationship was found between sleep duration and diseases including diabetes, hypertension and heart disease and depression. Short and long sleep durations and fragmented sleep were associated with increased odds of disease.

CONCLUSION

Six to eight hours of sleep, as well as less fragmented sleep, predicted better long-term metabolic and mental health.