Sleep quantity, sleep difficulties and their perceived consequences in a representative sample of some 2000 British adults

Sleep problems and sleep restriction are popular topics of discussion, but few representative data are available. We document Britain's sleep based on a nationally representative sample of 1997, 16-93 year olds, who participated in face-to-face interviews. Fifty-eight per cent of respondents reported sleep problems on one or more nights the previous week and 18% reported that the sleep they obtained was insufficient on the majority of nights. Sleep durations were longest in the youngest participants (16-24 years), who slept on average 1 h longer than the 7.04 (SD 1.55) sample average. Sleep duration showed no appreciable change beyond middle age. Men and women reported sleeping similar amounts but women reported more sleep problems. Men reported sleeping less when there were more children in their household. Workers (i.e. employees) reported sleeping less on workdays than on non-workdays, but those based at home and those not employed did not. Inability to switch off from work was related to sleep duration on non-workdays. Across all participants average sleep duration exhibited a non-monotonic association with quality of life (i.e. contribution of sleep to energy, satisfaction and success in work, home and leisure activities). Quality of life was positively associated with sleep duration, for durations up to 9 h, but negatively associated with quality of life beyond this. Comparison of our data with the US national sleep poll revealed that Britain sleeps as little or less, whereas a comparison with data reported 40 years ago revealed no statistically reliable reductions. Although we may not sleep less than four decades ago, when we report sleeping less we also tend to associate that lack of sleep with poor performance and quality of life.     

Rapid changes in overnight blood pressure after transitioning to early-morning shiftwork

Risk for adverse cardiovascular events increases when blood pressure does not decrease at night (“non-dipping,” <10% decrease from daytime blood pressure). Shiftwork alters relationships between behaviors and endogenous circadian rhythms (i.e., circadian disruption along with variable sleep timing), and chronic shiftwork increases cardiovascular disease risk. To determine whether transitioning into shiftwork changes the overnight blood pressure dipping pattern, we leveraged a natural experiment that occurs when newly-hired bus operators transition from a daytime training schedule into an early-morning shiftwork or daywork schedule. Twenty participants were studied in a 90-day protocol upon new employment and underwent cardio-metabolic health assessments, including ambulatory blood pressure monitoring, and weekly sleep-wake diaries. Measurements were repeated after ~30 and 90 days after transitioning to a day or an early-morning shiftwork schedule. Newly-hired shiftworkers displayed dramatic changes in overnight blood pressure, with 62% converting from a healthy dipping blood pressure to the nondipping pattern, resulting in 93% of shiftworkers displaying a nondipping phenotype at 90-days. In contrast, 50% of dayworkers had a nondipping profile at baseline and this decreased to 0% at 90-days, a significant difference from shiftworkers (p = .001). At 90-days, overnight blood pressure dipping was ~7% less in shiftworkers than dayworkers (–6.3% [95%CI –3.7 to –8.8%] vs –13.1% [–10.3 to –15.9%]: p < .01), with changes in dipping associated with changes in sleep timing variability (r² = .28, p = .03). The observed changes in overnight blood pressure dipping in newly-hired early-morning shiftworkers, which were associated with sleep timing variability, may be an early warning sign of increased cardiovascular risk among shiftworkers.     

Sleepiness and shiftwork: individual differences

SUMMARY  On-site studies of shiftwork show considerable differences in sleepiness between workers. Variation between individuals depends on different sleeping, coping and living habits of the workers, on possible sleep disorders, but also on more 'permanent' inter-individual factors that may influence sleepiness by changing either the circadian or homeostatic factors of sleep. The effects of circadian phase, age, sex, physical fitness, domestic and personality factors on shiftworkers' sleepiness and work-related accidents are reviewed. It is concluded that only a minor part of the variation in sleepiness between individuals can be explained. The present knowledge is not sufficient to carry out reliable 'selection' of individuals suitable for shiftwork. However, preventive advice and medical surveillance focusing on individual differences in sleepiness are recommended.     

A field study of age and gender differences in habitual adult sleep

The sleep of 52 healthy paid subjects (23 male) divided into three age-bands (20–34, 35–49 and 50–70 y) were recorded at night in their homes for a total of 190 subject-nights while following their normal daily activities and habitual sleep-wake schedule. There was a shortening in both nocturnal total sleep period and total sleep time (TST) with age, the oldest group sleeping 46 min less than the youngest. Also, the mid-point of sleep occurred 32 min earlier in the oldest group compared with the youngest group. The reduction in TST with age was due, in part, to increased wake periods within sleep. The youngest subjects showed more Movement Time which progressively decreased with age while the amount of stage 1 increased with age. The amount of slow-wave sleep (SWS, stages 3+4) was reduced, stage 4 was more than halved, while REM was slightly reduced with age. There were far fewer significant gender differences in the sleep variables: males, particularly in the middle and oldest age bands, had more stage 1 than females, while females had more SWS, particularly stage 3, than males. In general, despite relatively limited subject selection criteria, there was good agreement with previous laboratory-based normative sleep values for the effect of age and gender.     

Sleep paralysis episode frequency and number, types, and structure of associated hallucinations

Sleep paralysis (SP) episodes are often accompanied by vivid hallucinoid experiences that have been found to fall into three major categories thought to be organized according to intrinsic rapid eye movement (REM) processes. Prior research has, however, combined data for individuals with varying degrees of experience with SP episodes, rendering interpretations of the source of this structure ambiguous. The present study of 5799 current SP experients compares the nature and structure of the hallucinations of novice SP experients with those reporting varying numbers of episodes. Both qualitative and quantitative differences were found in reported hallucinations as a function of episode frequency, although the underlying three-factor structure of the hallucinoid experiences was highly similar for all groups. Novice experients' reports were, however, characterized by clearer differentiation of factors, likely because of a tendency of experienced SP experients to conflate experiences across episodes. Age and age of onset of SP episodes were associated with differences in the variety and types of hallucinations but not their underlying structure. Earlier onset of SP episodes was also associated with more frequent episodes. The results are consistent with the hypothesis that the basic form and patterning of hallucinatory experiences is a result of intrinsic processes, independent of prior experience, likely associated with underlying REM neurophysiology.     

Sleep disturbances as a predictor of cause-specific work disability and delayed return to work

Study Objective:

To examine sleep disturbances as a predictor of cause-specific work disability and delayed return to work.

Design:

Prospective observational cohort study linking survey data on sleep disturbances with records of work disability (≥ 90 days sickness absence, disability pension, or death) obtained from national registers.

Setting:

Public sector employees in Finland.

Participants:

56,732 participants (mean age 44.4 years, 80% female), who were at work and free of work disability at the study inception.

Measurements and Results:

During a mean follow-up of 3.3 years, incident diagnosis-specific work disability was observed in 4,028 (7%) employees. Of those, 2,347 (60%) returned to work. Sleep disturbances 5-7 nights per week predicted work disability due to mental disorders (hazard ratio [HR] 1.6, 95% confidence interval [CI] 1.3-1.9) and diseases of the circulatory system (HR = 1.6, 95% CI 1.2-2.1), musculoskeletal system (HR = 1.6, 95% CI 1.4-1.8) and nervous system (HR = 1.5, 95% CI 1.0-2.2), and injuries and poisonings (HR = 1.6, 95% CI 1.2-2.1) after controlling for baseline age, sex, socioeconomic status, night/shift work, health behaviors (e.g., smoking, exercise), diagnosed somatic diseases, use of pain killers, depression, and anxiety. In addition, sleep disturbances prior to disability were associated with higher likelihood of not returning to work after work disability from musculoskeletal diseases (HR = 1.2, 95% CI 1.1-1.7) and, in men, after work disability due to mental disorders (HR = 4.4, 95% CI 1.7-11.1).

Conclusions:

Sleep disturbances are associated with increased risk for subsequent disabling mental disorders and various physical illnesses. They also predict the outcome of work disability due to musculoskeletal disorders.

Citation:

Salo P; Oksanen T; Sivertsen B; Hall M; Pentti J; Virtanen M; Vahtera J; Kivimäki M. Sleep disturbances as a predictor of cause-specific work disability and delayed return to work. SLEEP 2010;33(10):1323-1331.     

Shiftworkers report worse sleep than day workers,even in retirement

The aim of this study was to explore how the level of shiftwork exposure during an individual's working life might be related to subjectively reported sleep quality and timing during retirement. Telephone interviews regarding past employment and sleep timing and quality (among other variables) were conducted using a pseudo‐random age‐targeted sampling process. Subjective sleep quality was assessed using a telephone version of the Pittsburgh Sleep Quality Index. Timing of reported habitual bedtimes and rise‐times were assessed using the Sleep Timing Questionnaire. Questions measuring morningness and subjective health were also given. Retired seniors (aged >65 years, n = 1113) were studied. Analysis was by analysis of variance, with shiftwork exposure in three bins [0 (n = 387), 1–15 (n = 371) and >15 years (n = 355)], gender (n = 634 male, 479 female) and former occupation [in two broad categories, ‘managerial’ (n = 437) versus ‘other’ (n = 676)] as factors. In retired shiftworkers, relative to retired day workers, past exposure to shiftwork was associated with higher (worse) PSQI scores by 1.0 units (1–15 years) and 0.6 units (>15 years) (main effect P = 0.005). There were also main effects of gender and former occupation (males and managerials reporting better sleep), but neither variable interacted with shiftwork exposure. The timing of current mean habitual bedtimes and rise‐times (and also the variance around them) were very similar for the three shiftwork exposure groups. The shiftwork exposure effect did not appear to be mediated by either morningness or current health. Prior exposure to shiftwork would appear to be related to currently reported sleep problems during retirement.     

Season of Birth,Gender, and Social-Cultural Effects on Sleep Timing Preferences in Humans

Study Objective:

The present study aimed to analyze season of birth effects on preferred sleep-wake cycle timing as assessed by Morningness-Eveningness Questionnaire (MEQ).

Participants and Measurements:

The MEQ was administered to a sample of 5,720 university students (3,851 Italians and 1,869 Spaniards; 3,877 female and 1,843 male; mean age 22.23 ± 2.98 years).

Results:

Females preferred to go to bed significantly earlier and sleep longer than males, regardless of season of birth and nationality. Subjects born in spring and summer went to bed and reached midpoint of sleep later than subjects born in fall and winter. Nationality significantly affected all the sleep parameters considered except duration.

Conclusion:

Overall, the effect of the season of birth on sleep preference timing was significant but quantitatively small. We suggest an evolutionary context for the different contributions of genetic and environmental factors in modulating sleep-wake cycles in humans.

Citation:

Natale V; Adan A; Fabbri M. Season of birth, gender, and social-cultural effects on sleep timing preferences in humans. SLEEP 2009;32(3):423–426.     

Moroccan lymphocyte subsets reference ranges: age,gender, ethnicity,and socio-economic factors dependent differences

ABSTRACT

Lymphocyte subsets reference ranges are helpful for a precise diagnosis and therapy of various diseases. We attempted in the current study to establish Moroccan lymphocyte reference range and reveal age, gender, ethnicity, income, and instructional levels dependent differences. Lymphocyte subsets percentage and absolute count were determined by 4-color flow cytometry in a population study of 145 adults Moroccan healthy volunteers. Analysis showed significant age-dependent changes. Age was associated with a decrease of naïve CD4+ and CD8+ T cells and an increase of memory CD4+ or CD8+ T cells. Activated CD4+ CD38+ and CD8+ CD38+ T cells, Treg as well as NK cell showed age-dependent alterations. In contrast, B cells remained unchanged. A higher percentage of CD3+ and CD4+ T cells was observed in females while CD8+, B and NK cells count were higher in men. Ethnicity, instructional levels, and personal income seem to not influence lymphocyte subsets reference values. This study provides reference ranges for lymphocyte subsets of healthy Moroccan adults. These results can be used for other North African (Maghrebian) countries considering their geographic, ethnic, economic, and cultural similarities.     

Adjustment of Circadian Rhythms and EEG Sleep Functions to Day and Night Sleep Among Permanent Nightworkers and Rotating Shiftworkers

Six workers on a permanent night work schedule and 6 workers on a weekly rotating day-night shift schedule were compared with regard to the quantity and quality of sleep as measured by EEG recordings, sleep diaries, and subjective ratings of sleep. They were also compared regarding the degree of adjustment of the body temperature rhythm and self-rated activation. The observations for all variables were made at the beginning, end, and after the end of the night shift period, and also in connection with free days. It was shown that compared to rotating shiftworkers the permanent nightworkers exhibited a better adjustment of the body temperature rhythm to night work and day sleep and also had fewer disturbances in sleep functions during day sleep. The rotating shiftworkers showed the poorest adjustment of the body temperature rhythm and sleep functions during day sleep at the beginning of the night shift week, whereas for permanent nightworkers corresponding, albeit less pronounced, disturbances were present in connection with night sleep. It was concluded that there was a close relationship between the degree of adjustment of the body temperature rhythm and EEG sleep functions, with a permanent night work schedule facilitating the adjustment to night work.     

Meta-analysis of age and actigraphy-assessed sleep characteristics across the lifespan

Study ObjectivesSleep quantity and continuity vary across the lifespan. Actigraphy is a reliable and widely used behavioral measure of sleep in research and personal health monitoring. This meta-analysis provides a novel examination of whether age (in years) is associated with actigraphy-assessed sleep across the lifespan.MethodsA systematic search of PubMed, Embase.com, Cochrane CENTRAL, and PsycINFO using “actigraphy” and “sleep” terms provided 7079 titles/abstracts; studies of individuals with known psychiatric or medical comorbidities were excluded. Ninety-one articles (N = 23 365) provided data for six meta-analyses examining sleep duration (k = 89), sleep efficiency (k = 58), bedtime (k = 19) and waketime (k = 9) for individuals ages 6–21, and bedtime (k = 7) and waketime (k = 7) for individuals ages 22 and older.ResultsAt older ages, sleep duration was shorter (r = −0.12) and sleep efficiency was lower (r = −0.05). Older age was associated with later bedtime (r = 0.37) and wake-up time (r = 0.24) from ages 6–21, whereas older age was associated with earlier bedtime (r = −0.66) and wake-up time (r = −0.59) for ages 22 and above. The strength of these associations was modified by study continent, but not by any other moderator.ConclusionsAge was negatively associated with actigraphy-assessed sleep duration and efficiency, but the effects were small in magnitude. On the other hand, large associations were observed between age and sleep timing, despite a smaller literature and the absence of analyzable data for ages 30–60. Changes in sleep timing, rather than changes in sleep duration or continuity, may better characterize the effects of age on human sleep.     

Sleep complaints in middle‐aged women and men: the contribution of working conditions and work–family conflicts

This study aimed to examine how physical working conditions, psychosocial working conditions and work–family conflicts are associated with sleep complaints, and whether health behaviours explain these associations. We used pooled postal questionnaire surveys collected in 2001–2002 among 40–60‐year‐old employees of the City of Helsinki (n = 5819, response rate 66%). Participants were classified as having sleep complaints if they reported sleep complaints at least once a week on average (24% of women and 20% of men). Independent variables included environmental work exposures, physical workload, computer work, Karasek’s job strain and work–family conflicts. Age, marital status, occupational class, work arrangements, health behaviours and obesity were adjusted for. Most working conditions were associated strongly with sleep complaints after adjustment for age only. After adjustment for work–family conflicts, the associations somewhat attenuated. Work–family conflicts were also associated strongly with women’s [odds ratio (OR) 5.90; confidence interval (CI) 4.16–8.38] and men’s sleep (OR 2.56; CI 1.34–4.87). The associations remained robust even after controlling for unhealthy behaviours, obesity, health status, depression and medications. Physically strenuous working conditions, psychosocial job strain and work–family conflicts may increase sleep complaints. Efforts to support employees to cope with psychosocial stress and reach a better balance between paid work and family life might reduce sleep complaints. Sleep complaints need to be taken into account in worksite health promotion and occupational health care in order to reduce the burden of poor sleep.     

性别、年龄和季节对血清25-羟维生素D水平的影响

目的探讨性别、年龄和季节对血清25-羟维生素D(25OHD)的影响。方法调取2014年12月至2018年10月北京协和医院血清25OHD检测结果,共计34062例。采用罗氏e601自动分析仪及其配套试剂检测血清25OHD。应用回归分析评估性别、年龄和季节对血清25OHD水平的影响。结果男性血清25OHD水平明显高于女性(P<0.001)。血清25OHD在8月份达到高峰为22.1 ng/mL。夏季对25OHD水平影响最大(标准化系数=0.273)。结论性别和季节显著影响血清25OHD水平。     

Cognitive Activity, Sleep Disturbance, and Stage Specific Differences Between Recorded and Reported Sleep

Sleepers were studied in their homes to obtain measures of relationships between (a) discrepancies between reported and recorded sleep, (b) degree of sleep difficulty, and (e) reported cognitive activity. Twelve good sleepers and 12 insomniacs were questioned immediately after lights out, at the occurrence of the first sleep spindle or K-complex, 10 min after the second sleep onset, 5 min after the onset of the first REM period, 10 min after the onset of the first stage 2, during subsequent periods of REM and stage 2 sleep, and at spontaneous arousals. Subjects responded to questions regarding mental content (thought vs picture, awake vs asleep, audience vs actor), estimated total time, and estimated total sleep time since the previous arousal. Insomniacs overestimated sleep difficulty only at 10 min after the second spindle and at spontaneous arousals. Reports of “picture” and “actor” were associated with sleeping difficulty. Persons who reported being “awake,”“actor,” and “picture” showed significantly greater discrepancies between reported and recorded sleep than persons who reported “sleep,”“audience,” or “thought”. The results are discussed in terms of implications for increased understanding of the phenomenon of insomnia.     

Effect of Varying the Time of Sleep on Sleep, Vigilance, and Self-Rated Activation

The effect of varying the time of sleep (2100-0500, 2400-0800, and 0300-1100 hrs) on the sleep, vigilance, and self-rated activation of 9 normal subjects was assessed. REM% increased, and Stage 2% decreased, with progressively later bedtimes. An hour by hour analysis showed, however, that the increase in REM sleep was confined to the second 3 hrs of sleep. Vigilance and self-rated activation, assessed 30 min after waking, at midday and in the early evening, did not differ between conditions but varied reliably with time of day. It is concluded that shifts away from the conventional 2400-0800 sleep period do not impair performance. Rather, the changes in sleep (between conditions) and performance (within conditions) are, in the main, consistent with the known circadian rhythms of REM sleep propensity and performance efficiency.     

Sleep duration and personality in Croatian twins

The objective of this study was to examine which genetic and environmental influences contribute to individual differences in sleep duration in a sample of Croatian adolescent/early adult twins, as well as to investigate the relationship between personality and sleep duration. Participants included 339 twin pairs (105 monozygotic and 234 dizygotic) aged between 15 and 22 years. They reported on their average sleep duration and personality. The broad heritability estimate (additive and non‐additive genetic influences) for sleep duration was 0.63, while personality estimates ranged between 0.47 and 0.62. Significant negative phenotypic associations with neuroticism and openness were mainly genetically mediated 100 and 80%, respectively. Only 6% of the sleep duration variance was explained by genetic influences shared with neuroticism and openness. In regression analysis, age, gender and five personality traits explained 5% of sleep duration variance, with neuroticism and openness as significant predictors. Comparison of short, moderate and long sleepers showed that participants in the short sleepers group had significantly higher neuroticism scores than groups of moderate and long sleepers, as well as a significantly higher openness score than the group of long sleepers. This indicates that personality traits of neuroticism and openness contribute to the prediction of sleep duration due to overlapping genetic influences that contribute to both these personality traits and sleep duration. However, as phenotypic overlap of personality and sleep duration is relatively weak, heritability of sleep duration is not only related to individual differences in personality traits, so future research needs to examine other phenotypic correlates of sleep duration.     

A Video Method to Study Drosophila Sleep

Study Objectives:

To use video to determine the accuracy of the infrared beam-splitting method for measuring sleep in Drosophila and to determine the effect of time of day, sex, genotype, and age on sleep measurements.

Design:

A digital image analysis method based on frame subtraction principle was developed to distinguish a quiescent from a moving fly. Data obtained using this method were compared with data obtained using the Drosophila Activity Monitoring System (DAMS). The location of the fly was identified based on its centroid location in the subtracted images.

Measurements and Results:

The error associated with the identification of total sleep using DAMS ranged from 7% to 95% and depended on genotype, sex, age, and time of day. The degree of the total sleep error was dependent on genotype during the daytime (P < 0.001) and was dependent on age during both the daytime and the nighttime (P < 0.001 for both). The DAMS method overestimated sleep bout duration during both the day and night, and the degree of these errors was genotype dependent (P < 0.001). Brief movements that occur during sleep bouts can be accurately identified using video. Both video and DAMS detected a homeostatic response to sleep deprivation.

Conclusions:

Video digital analysis is more accurate than DAMS in fly sleep measurements. In particular, conclusions drawn from DAMS measurements regarding daytime sleep and sleep architecture should be made with caution. Video analysis also permits the assessment of fly position and brief movements during sleep.

Citation:

Zimmerman JE; Raizen DM; Maycock MH; Maislin G; Pack AI. A video method to study drosophila sleep. SLEEP 2008;31(11):1587–1598.     

Women sleep objectively better than men and the sleep of young women is more resilient to external stressors: effects of age and menopause

The aims of this study were to: (i) assess gender differences of objective sleep patterns in a general population sample; (ii) evaluate the effects of menopause and hormone treatment (HT) on the sleep of the same cohort; and (iii) examine gender differences in sleep resilience towards external stressors. The participants were (i) 1324 subjects without sleep complaints, recruited from the general population of Central Pennsylvania that spent one night in the sleep laboratory and (ii) 66 young, healthy volunteers whose sleep was disturbed during night four by an external stressor, i.e. 24-h blood drawing (average of nights 2 and 3 versus night 4). Women compared with men in the general population sample had significantly higher percentage of sleep time, lower percentage of stage 1, and higher percentage of slow wave sleep. Also, menopause, in the absence of HT, was associated with prolonged sleep latency and decreased deep sleep. Finally, young, healthy women compared with men experienced less sleep disturbance because of blood draws as indicated by a significantly smaller change in per cent sleep time, and percentage of stage 1 sleep. These findings suggest that women without sleep complaints sleep objectively better across age than men and the sleep of young women is more resistant to external stressors. Also, gonadal hormones exert a beneficial effect on women's sleep. This gender dimorphism in sleep regulation may have been to protect women from the demands of infant and child care, and in part, might contribute to women's lower cardiovascular risks and greater longevity.     

Risks of preterm delivery and association with maternal age, birth order, and fetal gender.

The risk of preterm delivery in a recent sample (1990-1994) of Italian liveborns was examined, taking into account child birth order, and maternal age and education in addition to the fetal gender. Univariate analyses showed that a higher risk was associated with male than female babies, with first- than second-born children, with older mothers, and with less educated mothers. The relative weights of the factors examined were evaluated through logistic regression analyses and the highest and the lowest risks were found to be associated with advanced maternal age and male fetal gender respectively. Our findings therefore suggest that biological factors associated more with advanced maternal age than with the male gender of the fetus may influence premature onset of labour.     

Hypnotics and caffeine as countermeasures for shiftwork-related sleepiness and sleep disturbance

SUMMARY  Hypnotic medication reliably improves sleep during the day, in terms of increasing total sleep time (TST) and reducing awakenings and light sleep. Middle-aged individuals may benefit more than young adults. In addition, the time of day during which sleep is attempted may influence the efficacious dose of short-acting drugs. Available data suggest that improving sleep during the day may improve alertness/performance at night to a mild degree, but significant circadian-related sleepiness remains. Hypnotic medication may help minimize the cumulative effects of sleep loss associated with daytime sleep. Use for more than one week has not been adequately studied; however, as most night and rotating workers' schedules allow for night-time sleep for two or more nights per week, available evidence indicates that hypnotics can be used effectively on an intermittent basis, e.g. for the first 2–4 day-sleep periods of night shifts. Caffeine has been shown to increase alertness and improve psychomotor performance during usual night-shift hours when taken between 22.30 and 01.20 hours. Available data indicate that at approximate dosages of 250–400 mg, the beneficial effects persist until at least 05.30 hours. For most subjects, caffeine taken at the start of the night-shift does not interfere significantly with daytime sleep beginning at 09.00 hours. There is also some evidence that single doses of caffeine at the beginning of a night shift may be more alerting than divided doses. If caffeine is to be used therapeutically, avoidance of social use may be required to avoid tolerance to CNS stimulant effects. Despite the positive results of laboratory research examining hypnotics or caffeine as shiftwork countermeasures, field trials have not been conducted.