Homes Heat Health protocol: an observational cohort study measuring the effect of summer temperatures on sleep quality.

INTRODUCTION: Quality sleep is essential to our health and well-being. Summertime temperatures in the bedrooms of homes in temperate climates are increasing, especially in city apartments. There is very little empirical evidence of the effect of temperature on sleep when people are sleeping in their own bedroom. The Homes Heat Health project seeks to develop a measurable definition of temperature-related sleep disturbance and the effects on health, and so produce a credible criterion for identifying overheating in new and existing homes. METHODS AND ANALYSIS: A cohort of at least 95 people that live in London apartments and who are free of significant personal and health factors that could affect sleep are being recruited for an ongoing observational cohort study. A baseline questionnaire determines their customary sleep patterns and health. The geometrical form and thermal characteristics of their apartments is being recorded along with temperature, relative humidity and in some apartments CO2 levels, throughout one summer. Actigraphy records nightly sleep disturbance and every morning an app-based diary captures perceived sleep quality. Questionnaires following spells of hot weather capture changes in sleep pattern, sleep quality, and consequential health and well-being. ETHICS AND DISSEMINATION: The study protocol was approved by the Loughborough University ethics committee. The participants will receive both verbal and written information explaining the purpose of the study, what is expected of them, the incentives for participating and the feedback that will be provided. The results will be reported bi-annually to a project advisory board. Presentations will be made at conferences and the methods, intermediary and final results, in academic journals. Informing government bodies, professional organisations, construction industry representatives and housing providers is of particular importance.

Napping behaviour, daytime sleepiness, and arousal in high performance athletes and non-athlete controls.

Napping offers a strategy to manage sleep, aid recovery and enhance performance in elite sport. However, relatively little research attention has focussed on the natural history of athlete napping or tested the widely held assumption that athlete napping is mainly a consequence of degraded night-time sleep. Within a sample of 158 team (n = 76) and individual (n = 80) sport athletes, and 82 non-athlete controls, we analysed napping behaviour in relation to sleep quality, daytime sleepiness, and pre-sleep somatic and cognitive arousal. There was no significant association between athlete/non-athlete status and the prevalence, frequency, or duration of naps. Comparisons of athlete nappers and non-nappers found no significant differences in sleep quantity or quality. While nap propensity was significantly related to higher daytime sleepiness, this influence was moderated or augmented by levels of pre-sleep cognitive arousal. For some nappers, those with higher levels of arousal may need to be sleepier than those with lower levels of arousal in order to successfully initiate daytime sleep. Approximately 50% of athletes did not nap. If the benefits of athlete napping are to be fully exploited, the needs of this substantial group for whom napping may be problematic should be recognised and addressed.

Sleep Variability in UK Long Distance Heavy Goods Vehicle Drivers.

OBJECTIVES: Sleep variability levels are unknown in heavy goods vehicle (HGV) drivers yet are associated with adverse health outcomes and reduced driver vigilance when high. METHODS: Two hundred and thirty-three HGV drivers recruited across 25 UK depots provided sleep variability, sleep duration, and sleep efficiency data via wrist-worn accelerometry (GENEActiv) over 8 days. Sleep variability indicators included social jetlag (the difference in midpoint of the sleep window between work and nonworkdays) and intraindividual variability of sleep window onset time, out-of-bed time, and sleep duration. RESULTS: Fifty-three percent of drivers experienced social jetlag (≥1 hour), and 27% experienced high (>2 hours) social jetlag. Drivers with the highest sleep variability had the shortest sleep duration and lowest sleep efficiency during workdays. CONCLUSIONS: Drivers with high sleep variability may experience more fatigue when driving given the poor sleep outcomes during workdays observed.

Altered Core Temperature and Salivary Melatonin in Athletes with a Cervical Spinal Cord Injury.

Sleep disturbances are common in athletes with a cervical spinal cord injury (cSCI) and may be associated with circadian alterations. Therefore, the purpose of this study was to compare physiological circadian outputs between athletes with a cSCI and non-disabled controls (CON). Eight male wheelchair athletes with a cSCI and eight male CON (30±4 and 30±6 yrs, respectively) had their core body temperature (Tcore), skin temperature (Tskin), and salivary melatonin measured during a 24 h period. In the cSCI group, daytime Tcore was significantly lower (36.5 (0.2) vs 36.9 (0.3)°C; p=0.02) and time of the Tcore sleep minimum was significantly earlier (23:56±00:46 vs 02:39 ± 02:57; p=0.04). The athletes with a cSCI had significantly lower Tcore values during the beginning of the night compared with the CON group, but their Tcore increased at a greater rate, thereafter, indicated by a significant time/group interaction (p=0.04). Moreover, the cSCI group did not display a salivary melatonin response and exhibited significantly lower concentrations at 22:00 (p=0.01) and 07:00 (p=0.01) compared with the CON group. Under natural living conditions, athletes with a cSCI displayed circadian changes in the Tcore rhythm and nocturnal melatonin production.

Sleep duration and sleep efficiency in UK long-distance heavy goods vehicle drivers.

OBJECTIVES: To profile sleep duration and sleep efficiency in UK long-distance heavy goods vehicle (HGV) drivers and explore demographic, occupational and lifestyle predictors of sleep. METHODS: Cross-sectional analyses were carried out on 329 HGV drivers (98.5% men) recruited across an international logistics company within the midland's region, UK. Sleep duration and efficiency were assessed via wrist-worn accelerometry (GENEActiv) over 8 days. Proportions of drivers with short sleep duration (<6 hour/24 hours and <7 hour/24 hours) and inadequate sleep efficiency (<85%) were calculated. Demographic, occupational and lifestyle data were collected via questionnaires and device-based measures. Logistic regression assessed predictors of short sleep duration and inadequate sleep efficiency. RESULTS: 58% of drivers had a mean sleep duration of <6 hour/24 hours, 91% demonstrated <7-hour sleep/24 hours and 72% achieved <85% sleep efficiency. Sleeping <6 hour/24 hours was less likely in morning (OR 0.45, 95% CI 0.21 to 0.94) and afternoon (OR 0.24, CI 0.10 to 0.60) shift workers (vs night) and if never smoked (vs current smokers) (OR 0.45, CI -0.22 to 0.92). The likelihood of sleeping <7 hour/24 hours reduced with age (OR 0.92, CI 0.87 to 0.98). The likelihood of presenting inadequate sleep efficiency reduced with age (OR 0.96, CI 0.93 to 0.99) and overweight body mass index category (vs obese) (OR 0.47, CI 0.27 to 0.82). CONCLUSIONS: The high prevalence of short sleep duration and insufficient sleep quality (efficiency) rate suggest that many HGV drivers have increased risk of excessive daytime sleepiness, road traffic accidents and chronic disease. Future sleep research in UK HGV cohorts is warranted given the road safety and public health implications.

Sleep extension and metabolic health in male overweight/obese short sleepers: A randomised controlled trial.

While limited evidence suggests that longer sleep durations can improve metabolic health in habitual short sleepers, there is no consensus on how sustained sleep extension can be achieved. A total of 18 men (mean [SD] age 41 [ 9] years), who were overweight/obese (mean [SD] body mass index 30 [3] kg/m2 ) and short sleepers at increased risk of type 2 diabetes were randomised to a 6-week sleep-extension programme based on cognitive behavioural principles (n = 10) or a control (n = 8) group. The primary outcome was 6-week change in actigraphic total sleep time (TST). Fasting plasma insulin, insulin resistance (Homeostatic Model Assessment for Insulin Resistance [HOMA-IR]), blood pressure, appetite-related hormones from a mixed-meal tolerance test, and continuous glucose levels were also measured. Baseline to 6-week change in TST was greater in the sleep-extension group, at 79 (95% confidence interval [CI] 68.90, 88.05) versus 6 (95% CI -4.43, 16.99) min. Change in the sleep-extension and control groups respectively also showed: lower fasting insulin (-11.03 [95% CI -22.70, 0.65] versus 7.07 [95% CI -4.60, 18.74] pmol/L); lower systolic (-11.09 [95% CI -17.49, -4.69] versus 0.76 [95% CI -5.64, 7.15] mmHg) and diastolic blood pressure (-12.16 [95% CI -17.74, -6.59] versus 1.38 [95% CI -4.19, 6.96] mmHg); lower mean amplitude of glucose excursions (0.34 [95% CI -0.57, -0.12] versus 0.05 [95% CI -0.20, 0.30] mmol/L); lower fasting peptide YY levels (-18.25 [95%CI -41.90, 5.41] versus 21.88 [95% CI -1.78, 45.53] pg/ml), and improved HOMA-IR (-0.51 [95% CI -0.98, -0.03] versus 0.28 [95% CI -0.20, 0.76]). Our protocol increased TST and improved markers of metabolic health in male overweight/obese short sleepers.

Sleep Characteristics of Highly Trained Wheelchair Rugby Athletes With and Without a Cervical Spinal Cord Injury During the Competitive Season.

Sleep behaviors although significantly relevant to exercise recovery are poorly characterized in Para-sport athletes. Therefore, the main aims of this study were to describe sleep quality and quantity of highly trained wheelchair rugby (WR) athletes during the competitive season, and to investigate whether impairment type or attending a training camp influenced sleep outcomes. Eighteen male WR athletes (mean ± SD; age: 30 ± 5 years) with cervical spinal cord injuries (n = 11) (CSCI) and without (n = 7) (NON-SCI) wore an activity monitor over a 16-day period to objectively quantify sleep parameters, while the Pittsburgh Sleep Quality Index (PSQI) and nightly sleep diary entries were used as subjective means. A sub-sample of the athletes (n = 11) had their sleep monitored during a 3-night training camp to assess the impact of environmental change on sleep. Furthermore, as an additional exploratory measure core temperature was measured for a single night-time period using ingestible telemetry capsules. The athletes had total sleep times and sleep efficiency scores of 7.06 (1.30) h.min [median (interquartile range)] and 81 (9)%, respectively. Sleep onset latency and wake after sleep onset were 13 (24) min and 1.11 (0.45) h.min, respectively. No significant differences were found in objective sleep variables between the impairment groups despite the CSCI group being significantly more likely to report a poorer night's sleep (p = 0.04). Furthermore, attending the training camp caused a significant reduction in total sleep time for both groups [Δ38 ± 33 min; (95% CI: 18-60 min) p < 0.01]. This study highlights suboptimal sleep characteristics that are present in both CSCI and NON-SCI wheelchair athletes, as defined by the National Sleep Foundation. Although objective scores did not differ between groups, athletes with a CSCI rated their sleep worse. Furthermore, the disruption of sleep during training camp reflects an additional risk factor that is important to recognize for those working with wheelchair athletes.

Psychomotor Performance Decrements following a Successful Physical Activity Intervention for Insomnia.

Objectives: Evidence supports the view that reductions in cognitive hyperarousal contribute substantially to improved sleep outcomes following cognitive and behavioral interventions for insomnia disorder. Assuming an inverted-u relationship between arousal and performance, a theoretical possibility, supported by limited empirical data, is that the same mediating processes could negatively impact aspects of psychomotor performance, reducing speed on tests of reaction time. Participants: Sedentary participants (mean age = 59.8; SD = 9.46) meeting research diagnostic criteria for insomnia were randomized to either an exercise intervention of ≥150 min of moderate-intensity activity per week (n = 20), or a wait-list control group (n = 21). Of these, n = 17 intervention and n = 18 control participants completed 6-month follow-up assessments. Methods: Digit span, and simple and complex vigilance task performance was assessed using a computerized protocol at baseline and 6-month follow-up. Dependent variables included digit span, simple reaction time (SRT), complex reaction time (CRT), false positive responses, number of lapses, and SRT/CRT ratio (indicative of the magnitude of difference between simple and complex RT performance). The primary clinical outcome was Insomnia Severity Index (ISI) score. Results: In comparisons of baseline to follow-up change, ISI scores showed clinically significant improvement in the intervention group at 6-month follow-up (F (8,26) = 5.16; P = 0.03). Baseline vigilance performance was equivalent in both groups. At 6-month follow-up, however, the intervention group showed significantly slower simple reaction time F(4,30) = 10.25, p < 0.01, and a significantly decreased SRT/CRT ratio (F(4,30) = 13.22, p < 0.01). Conclusions: Among people meeting diagnostic criteria for insomnia, beneficial sleep outcomes following successful behavioral interventions may, under some circumstances, come at the cost of slower psychomotor performance.

Regular physical activity and insomnia: An international perspective.

Both very low and very high levels of regular physical activity have been associated with degraded sleep quality. Cross-national variations in habitual physical activity levels, therefore, may contribute to cross-national differences in insomnia prevalence. The present study assesses and compares the extent to which weekly durations of moderate-intensity physical activity contribute to insomnia risk. Demographic, sleep, physical activity and general health profiles were obtained from a convenience sample of 9,238 adults drawn from five countries (South Africa, Australia, China, South Korea and the UK) using social media. Insomnia prevalence, using DSM-5 criteria, ranged from 4.1% (China) to 14.8% (UK). Evaluating risk using logistic regression adjusted only for age and gender, the lowest level of activity (<10 continuous min per week) was associated with significant insomnia risk (odds ratio = 1.37; 95% confidence interval = 1.05-1.79; p < 0.05). However, when adjusted for all covariates except country, only the highest level of physical activity (>300 min per week) was associated with significantly increased insomnia risk (odds ratio = 1.30; 95% confidence interval = 1.03-2.51; p < 0.05). Risk associated with high activity remained after the addition of "country" to the model (odds ratio = 1.31; 95% confidence interval = 1.02-1.69; p < 0.05). Across all models, female gender, low-rated health, low education and older age consistently increased insomnia risk. These cross-national data indicate that extremes of inactivity/activity can significantly influence insomnia risk independent of country. Insomnia risk associated with very low levels of activity may be mediated by poorer health and disadvantageous social status. However, while very high levels of activity increase insomnia risk independent of health and demographic factors, they may also confound with personally and occupationally demanding lifestyles.

Sleep duration and all-cause mortality: links to physical activity and prefrailty in a 27-year follow up of older adults in the UK.

OBJECTIVES: To assess sleep duration-mortality relationships across a 27-year follow-up period in a well characterized random sample of older people, and to test the hypothesis that mortality risks associated with long sleep duration confound with, and can be explained by, low levels of functional capacity indicative of frailty. METHODS: Face-to-face interviews conducted among 1002 randomly sampled older (65+) people in 1985 provided baseline profiles of health, functional capacity, physical activity, and sleep quality and duration. Health and functional status in each of 6 sleep duration categories (≤4, 5, 6, 7, 8, ≥9 h) was examined. At censorship in 2012, 927 deaths were recorded. Relationships between sleep duration and 27-year all-cause mortality were then examined in a series of incrementally adjusted Cox regression models. RESULTS: Associations between sleep duration and measures of sleep quality were predominantly linear, with longer sleep times indicating superior sleep quality. Relationships between sleep duration and functional capacity, on the other hand, were predominantly quadratic, with most approximating a U-shaped function. Adjusted for age, gender, social class, insomnia symptoms, physical health, depression, BMI and smoking status, long sleep duration and continuous hypnotic drug use at baseline were significantly and independently associated with elevated mortality risk (HR: 1.37; 95% CI: 1.05-1.78; HR: 1.24; 95% CI: 1.01-1.51). When indices of frailty were added to the model, hazard ratios for long sleep duration and hypnotic drug became non-significant, while the lowest physical activity quintile and very slow walking speed significantly increased mortality risk (HR: 1.79; 95% CI: 1.40-2.30; HR: 1.41; 95% CI: 1.15-1.73 respectively). CONCLUSIONS: In analyses of sleep-related mortality outcomes long sleep durations confound with, and may be indicative of, incipient frailty among older participants.

Sleep Quality and Recommended Levels of Physical Activity in Older People.

A minimum level of activity likely to improve sleep outcomes among older people has not previously been explored. In a representative UK sample aged 65+ (n = 926), cross-sectional regressions controlling for appropriate confounders showed that walking at or above the internationally recommended threshold of ≥ 150 min per week was significantly associated with a lower likelihood of reporting insomnia symptoms (OR = 0.67, 95% CI = 0.45-0.91, p < .05). At a 4-year follow-up (n = 577), higher walking levels at baseline significantly predicted a lower likelihood of reporting sleep onset (OR = 0.64, 95% CI = 0.42-0.97, p < .05) or sleep maintenance (OR = 0.63, 95% CI = 0.41-0.95, p < .05) problems. These results are consistent with the conclusion that current physical activity guidelines can support sleep quality in older adults.

Increased physical activity improves sleep and mood outcomes in inactive people with insomnia: a randomized controlled trial.

While high levels of activity and exercise training have been associated with improvements in sleep quality, minimum levels of activity likely to improve sleep outcomes have not been explored. A two-armed parallel randomized controlled trial (N=41; 30 females) was designed to assess whether increasing physical activity to the level recommended in public health guidelines can improve sleep quality among inactive adults meeting research diagnostic criteria for insomnia. The intervention consisted of a monitored program of ≥150 min of moderate- to vigorous-intensity physical activity per week, for 6 months. The principal end-point was the Insomnia Severity Index at 6 months post-baseline. Secondary outcomes included measures of mood, fatigue and daytime sleepiness. Activity and light exposure were monitored throughout the trial using accelerometry and actigraphy. At 6 months post-baseline, the physical activity group showed significantly reduced insomnia symptom severity (F(8,26) = 5.16, P = 0.03), with an average reduction of four points on the Insomnia Severity Index; and significantly reduced depression and anxiety scores (F(6,28) = 5.61, P = 0.02; and F(6,28) = 4.41, P = 0.05, respectively). All of the changes were independent of daily light exposure. Daytime fatigue showed no significant effect of the intervention (F(8,26) = 1.84, P = 0.18). Adherence and retention were high. Internationally recommended minimum levels of physical activity improve daytime and night-time symptoms of chronic insomnia independent of daily light exposure levels.