Ambulatory activity monitoring during sleep: an evaluation of internight and intrasubject variability in healthy persons aged 50-98 years

Bedtime regularity predicts positive affect among veterans with posttraumatic stress disorder: an ecological momentary assessment study

BACKGROUND

Regularizing bedtime and out-of-bed times is a core component of behavioral treatments for sleep disturbances common among patients with posttraumatic stress disorder (PTSD). Although improvements in subjective sleep complaints often accompany improvements in PTSD symptoms, the underlying mechanism for this relationship remains unclear. Given that night-to-night sleep variability is a predictor of physical and mental well-being, the present study sought to evaluate the effects of bedtime and out-of-bed time variability on daytime affect and explore the optimal window lengths of over which variability is calculated.

METHODS

For about 30 days, male U.S. military veterans with PTSD (N = 64) in a residential treatment program provided ecological momentary assessment data on their affect and slept on beds equipped with mattress actigraphy. We computed bedtime and out-of-bed time variability indices with varying windows of days. We then constructed multilevel models to account for the nested structure of our data and evaluate the impact of bedtime and out-of-bed time variability on daytime affect.

RESULTS

More regular bedtime across 6-9 days was associated with greater subsequent positive affect. No similar effects were observed between out-of-bed time variability and affect.

CONCLUSIONS

Multiple facets of sleep have been shown to differently predict daily affect, and bedtime regularity might represent one of such indices associated with positive, but not negative, affect. A better understanding of such differential effects of facets of sleep on affect will help further elucidate the complex and intertwined relationship between sleep and psychopathology.

TRIAL REGISTRATION

The trial retrospectively was registered on the Defense Technical Information Center website: Award # W81XWH-15-2-0005.

Associations between cognitive function, actigraphy-based and self-reported sleep in older community-dwelling adults: Findings from the Irish Longitudinal Study on Ageing

OBJECTIVE

Cognitive impairment is prevalent in older ages. Associations with sleep are well established; however, ambiguity remains in which sleep characteristics contribute to this impairment. We examined cross-sectional associations between both self-reported and actigraphy-based sleep and cognitive performance across a number of domains in community-dwelling older adults.

METHODS

1520 participants aged 50 and older with self-reported and actigraphy-based total sleep time (TST) (≤5, 6, 7-8, 9 and ≥10 h) and self-reported sleep problems were analysed. Cognitive function was assessed using the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), verbal fluency, immediate and delayed recall memory, colour trails tests, and choice reaction tests (CRT). Associations between sleep and cognition were modelled using linear and negative binomial regression.

RESULTS

Negative associations were found between ≥10 h of self-reported TST and MoCA error rate (incidence rate ratio [IRR] = 1.42; 95% confidence interval [CI] = 1.18, 1.71; p < 0.001); verbal fluency (beta [B] = -2.32 words; 95% CI = -4.00, -0.65; p < 0.01); and delayed recall (B = -0.91 words; 95% CI = -1.58, -0.25; p < 0.05) compared to 7-8 h. Significant associations with actigraphy-based TST were limited to MoCA error rate in ≤5 h (IRR = 1.22; 95% CI = 1.02, 1.45; p < 0.05) compared to 7-8 h. Higher numbers of sleep problems were associated with slower performance in CRT cognitive response time (IRR = 1.02; 95% CI = 1.00, 104; p < 0.05) and total response time (IRR = 1.02; 95% CI = 1.00, 1.04; p < 0.05).

CONCLUSIONS

Self-reported long sleep duration was consistently associated with worse cognitive performance across multiple domains. Marginal associations between cognition and both actigraphy-based sleep and self-reported sleep problems were also apparent. These results further affirm poor sleep as a risk factor for cognitive impairment.

The First-Night Effect in Elite Sports: An Initial Glance on Polysomnography in Home-Based Settings

Self-applied portable polysomnography is considered a promising tool to assess sleep architecture in field studies. However, no findings have been published regarding the appearance of a first-night effect within a sport-specific setting. Its absence, however, would allow for a single night sleep monitoring and hence minimize the burden on athletes while still obtaining the most important variables. For this reason, the aim of the study was to assess whether the effect appears in home-based sleep monitoring of elite athletes. The study sample included eight male and 12 female German elite athletes from five different sports. Participants slept with a portable polysomnography for two nights, which they self-applied at night before going to bed. Time in bed and wake-up time in the morning were freely chosen by each individual athlete without any restrictions regarding time or sleeping environment. Participants were asked to keep the same location and time frame during the two days of monitoring and stick to their usual sleeping schedules. Sleep stages were manually scored using 30-s epochs. Sleep parameters and stages were later compared with the help of linear mixed models to investigate the factor time. Significant differences between the two nights were found for percentage of Non-REM sleep [T(19) = -2,10, p < 0.05, d = -0.47, 95%-CI (-7.23, -0.01)] with small effect size, Total Wake Time [T(19) = 2.30, p = 0.03, d = 0.51, 95%-CI (1.66, 35.17)], Sleep Efficiency [T(19) = -2.48, p = 0.02, d = -0.55, 95%-CI (-7.43, -0.63)], and Wake percentage [T(19) = 2.47, p = 0.02, d = 0.55, 95%-CI (0.61, 7.43)] with moderate effect sizes, and N3 Sleep Onset Latency [T(19) = 3.37, p < 0.01, d = 0.75, 95%-CI (7.15, 30.54)] with large effect size. Confidence Intervals for all other indices range from negative to positive values and hence specify, that parameters were not systematically negatively affected in the first night. Findings suggest that some individuals are more affected by the first-night effect than others. Yet, in order to keep the measurement uncertainties to a minimum, a more conservative approach with at least two monitoring nights should be used whenever possible, if no other supporting information on the athletes says otherwise.

Intraindividual variability in sleep and comorbid medical and mental health conditions

STUDY OBJECTIVES

Intraindividual variability (IIV) in sleep may be a risk factor for disease above the influence of mean sleep. Associations between IIV in sleep and risk for a comprehensive set of common medical and mental health conditions have not been assessed in a representative sample.

METHODS

This study examined mean and IIV in total sleep time (TST), sleep quality (SQ), sleep efficiency (SE), and circadian midpoint (CM) in 771 adults recruited for an epidemiological study. Participants completed 14 days of sleep diaries to assess TST, SQ, SE, and CM, after which they reported on medical conditions and mental health symptoms. Data were analyzed using logistic regression, and models controlled for gender, body mass index, age, and race.

RESULTS

Lower mean TST, SQ, and SE were related to increased odds of having gastrointestinal problems, depression, and anxiety. IIV in TST was related to increased odds of having neurological, breathing, and gastrointestinal problems, as well as pain and depression; all results held controlling for mean sleep and adjusting for false discovery rate. IIV in SQ and SE was not associated with odds of having any medical or mental health conditions after adjusting for false discovery rate, nor was IIV in CM or mean CM.

CONCLUSIONS

Confirming previous research, mean TST, SQ, and SE are related to risk for gastrointestinal problems, depression, and anxiety. IIV in TST may be a unique facet of disturbed sleep that is associated with increased risk for a diverse cluster of medical and mental health conditions.

The Effect of Structured Exercise on Sleep During the Corresponding Night Among Older Women in an Exercise Program

This study investigated the acute effect of exercise on sleep outcomes among healthy older women by comparing days with structured exercise versus days without structured exercise during 4 months of exercise training. Participants (n = 51) in this study had wrist-worn actigraphic sleep data available following at least 3 days with structured exercise and 3 days without structured exercise at mid-intervention and at the end of intervention. The exercise intervention was treadmill walking. Multilevel models were used to examine whether structured exercise impacted sleep outcomes during the corresponding night. Overall, 1,362 nights of data were included in the analyses. In unadjusted and adjusted models, bedtimes were significantly earlier on evenings following an acute bout of structured exercise than on evenings without structured exercise. No other sleep parameters differed between exercise and nonexercise days. Understanding the effects of exercise on sleep in this understudied population may help to improve their overall sleep quality.

Sleep variability and nighttime activity among Tsimane forager-horticulturalists

OBJECTIVES

A common presumption in sleep research is that "normal" human sleep should show high night-to-night consistency. Yet, intra-individual sleep variation in small-scale subsistence societies has never been studied to test this idea. In this study, we assessed the degree of nightly variation in sleep patterns among Tsimane forager-horticulturalists in Bolivia, and explored possible drivers of the intra-individual variability.

METHODS

We actigraphically recorded sleep among 120 Tsimane adults (67 female), aged 18-91, for an average of 4.9 nights per person using the Actigraph GT3X and Philips Respironics Actiwatch 2. We assessed intra-individual variation using intra-class correlations and average deviation from each individual's average sleep duration, onset, and offset times ( ɛ¯).

RESULTS

Only 31% of total variation in sleep duration was due to differences among different individuals, with the remaining 69% due to nightly differences within the same individuals. We found no statistically significant differences in Tsimane sleep duration by day-of-the-week. Nightly variation in sleep duration was driven by highly variable sleep onset, especially for men. Nighttime activities associated with later sleep onset included hunting, fishing, housework, and watching TV.

CONCLUSIONS

In contrast to nightly sleep variation in the United States being driven primarily by "sleeping-in" on weekends, Tsimane sleep variation, while comparable to that observed in the United States, was driven by changing "bedtimes," independent of day-of-the-week. We propose that this variation may reflect adaptive responses to changing opportunity costs to sleep/nighttime activity.

Selection for long and short sleep duration in Drosophila melanogaster reveals the complex genetic network underlying natural variation in sleep

Why do some individuals need more sleep than others? Forward mutagenesis screens in flies using engineered mutations have established a clear genetic component to sleep duration, revealing mutants that convey very long or short sleep. Whether such extreme long or short sleep could exist in natural populations was unknown. We applied artificial selection for high and low night sleep duration to an outbred population of Drosophila melanogaster for 13 generations. At the end of the selection procedure, night sleep duration diverged by 9.97 hours in the long and short sleeper populations, and 24-hour sleep was reduced to 3.3 hours in the short sleepers. Neither long nor short sleeper lifespan differed appreciably from controls, suggesting little physiological consequences to being an extreme long or short sleeper. Whole genome sequence data from seven generations of selection revealed several hundred thousand changes in allele frequencies at polymorphic loci across the genome. Combining the data from long and short sleeper populations across generations in a logistic regression implicated 126 polymorphisms in 80 candidate genes, and we confirmed three of these genes and a larger genomic region with mutant and chromosomal deficiency tests, respectively. Many of these genes could be connected in a single network based on previously known physical and genetic interactions. Candidate genes have known roles in several classic, highly conserved developmental and signaling pathways—EGFR, Wnt, Hippo, and MAPK. The involvement of highly pleiotropic pathway genes suggests that sleep duration in natural populations can be influenced by a wide variety of biological processes, which may be why the purpose of sleep has been so elusive.

One of the biggest mysteries in biology is the need to sleep. Sleep duration has an underlying genetic basis, suggesting that very long and short sleep times could be bred for experimentally. How far can sleep duration be driven up or down? Here we achieved extremely long and short night sleep duration by subjecting a wild-derived population of Drosophila melanogaster to an experimental breeding program. At the end of the breeding program, long sleepers averaged 9.97 hours more nightly sleep than short sleepers. We analyzed whole-genome sequences from seven generations of the experimental breeding to identify allele frequencies that diverged between long and short sleepers, and verified genes and genomic regions with mutation and deficiency testing. These alleles map to classic developmental and signaling pathways, implicating many diverse processes that potentially affect sleep duration.

A novel approach using actigraphy to quantify the level of disruption of sleep by in-home polysomnography: the MrOS Sleep Study: Sleep disruption by polysomnography

BACKGROUND

The "first-night effect" of polysomnography (PSG) has been previously studied; however, the ability to quantify the sleep disruption level has been confounded with the use of PSG on all nights. We used actigraphy to quantify disruption level and examined characteristics associated with disruption.

METHODS

Totally, 778 older men (76.2 ± 5.4 years) from a population-based study at six US centers underwent one night of in-home PSG. Actigraphy was performed on the PSG night and three subsequent nights. Actigraphically measured total sleep time (TST), sleep efficiency (SE), wake after sleep onset (WASO), and sleep onset latency (SOL) from the PSG night and subsequent nights were compared. Linear regression models were used to examine the association of characteristics and sleep disruption.

RESULTS

On average, sleep on the PSG night was worse than the following night (p < 0.05, TST 21 ± 85 min less, SE 2.3 ± 11.3% less, WASO 4.9 ± 51.8 min more, SOL 6.6 ± 56.2 min more). Sleep on the PSG night was significantly worse than that two and three nights later. Characteristics associated with greater sleep disruption on the PSG night included older age, higher apnea-hypopnea index, worse neuromuscular function, and more depressive symptoms. Minorities and men with excessive daytime sleepiness slept somewhat better on the PSG night.

CONCLUSIONS

Among older men, there was sleep disruption on the PSG night, which may lead to sleep time underestimation. The increase of sleep on the night after the PSG suggests that data from the second monitoring may overestimate sleep.

The Impact of a Cognitive Behavioral Pain Management Program on Sleep in Patients with Chronic Pain: Results of a Pilot Study

OBJECTIVE

To determine the impact of a cognitive behavioral pain management program on sleep in patients with chronic pain.

DESIGN

Prospective nonrandomized controlled pilot study with evaluations at baseline and 12 weeks.

SETTING

Out-patient multidisciplinary cognitive behavioral pain management program in a university teaching hospital.

SUBJECTS

Patients with chronic pain who fulfilled the criteria for participation in a cognitive behavioral pain management program.

METHODS

Patients assigned to the intervention group (n = 24) completed a 4 week cognitive behavioral pain management program, and were compared with a waiting list control group (n = 22). Assessments for both groups occurred at baseline and two months post cognitive behavioral pain management program. Outcome measures included self-report (Pittsburgh Sleep Quality Index) and objective (actigraphy) sleep measures, pain and quality of life measures.

RESULTS

Both groups were comparable at baseline, and all had sleep disturbance. The Pittsburgh Sleep Quality Index correlated with only two of the seven objective sleep measures (fragmentation index r = 0.34, P = 0.02, and sleep efficiency percentage r = -0.31, P = 0.04). There was a large treatment effect for cognitive behavioral pain management program group in mean number of wake bouts (d = 0.76), where a significant group*time interaction was also found (P = 0.016), showing that the CBT-PMP group improved significantly more than controls in this sleep variable.

CONCLUSIONS

Patients attending a cognitive behavioral pain management program have high prevalence of sleep disturbance, and actigraphy technology was well tolerated by the patients. Preliminary analysis of the impact of a cognitive behavioral pain management program on sleep is promising, and warrants further investigation.

Objective but not subjective sleep predicts memory in community-dwelling older adults

Research on the relationship between habitual sleep patterns and memory performance in older adults is limited. No previous study has used objective and subjective memory measures in a large, older-aged sample to examine the association between sleep and various domains of memory. The aim of this study was to examine the association between objective and subjective measures of sleep with memory performance in older adults, controlling for the effects of potential confounds. One-hundred and seventy-three community-dwelling older adults aged 65-89 years in Victoria, Australia completed the study. Objective sleep quality and length were ascertained using the Actiwatch 2 Mini-Mitter, while subjective sleep was measured using the Pittsburgh Sleep Quality Index. Memory was indexed by tests of retrospective memory (Hopkins Verbal Learning Test - Revised), working memory (n-back, 2-back accuracy) and prospective memory (a habitual button pressing task). Compared with normative data, overall performance on retrospective memory function was within the average range. Hierarchical regression was used to determine whether objective or subjective measures of sleep predicted memory performances after controlling for demographics, health and mood. After controlling for confounds, actigraphic sleep indices (greater wake after sleep onset, longer sleep-onset latency and longer total sleep time) predicted poorer retrospective (∆R(2)  = 0.05, P = 0.016) and working memory (∆R(2)  = 0.05, P = 0.047). In contrast, subjective sleep indices did not significantly predict memory performances. In community-based older adults, objectively-measured, habitual sleep indices predict poorer memory performances. It will be important to follow the sample longitudinally to determine trajectories of change over time.

Beyond mean values: Quantifying intraindividual variability in pre-sleep arousal and sleep in younger and older community-dwelling adults

Intraindividual variability is an often understudied aspect of health outcomes research that may provide additional, complementary information to average values. The current paper aims to further our understanding of intraindividual variability in health research by presenting the results of a daily diary study of sleep and pre-sleep arousal. Pre-sleep arousal is often implicated in poor sleep outcomes, although the arousal–sleep association is not uniform across age groups. The examination of intraindividual variability in different age groups may provide a more complete understanding of these constructs, which, in turn, can inform future research. The overall objectives of the current study are to quantify the amount of intraindividual variability in pre-sleep arousal and sleep and to examine age differences in this variability. A sample of older (n=50) and younger (n=50) adults recruited from North Central Florida and online completed 14-consecutive-day diaries assessing pre-sleep arousal and sleep outcomes. Significant age differences were found for sleep and pre-sleep arousal; older adults displayed poorer, more variable sleep for the majority of sleep outcomes, and higher levels of pre-sleep arousal than younger adults. The high amount of intraindividual variability has implications for the assessment of pre-sleep arousal and sleep across age groups.

Temporal relationships between physical activity and sleep in older women

PURPOSE

The objective of this study is to examine the temporal and bidirectional relationships between accelerometer-derived physical activity estimates and actigraphy-assessed sleep characteristics among older women.

METHODS

A subgroup of participants (N = 143, mean age = 73 yr) enrolled in the Healthy Women Study wore an ActiGraph accelerometer on their waist and an Actiwatch sleep monitor on their wrist concurrently for seven consecutive days. Multilevel models examined whether ActiGraph-assessed daily activity counts (ct·min⁻¹·d⁻¹) and moderate- to vigorous-intensity physical activity (MVPA; min·d⁻¹) predicted Actiwatch-assessed sleep onset latency, total sleep time, sleep efficiency, and sleep fragmentation. Similar models were used to determine whether nighttime sleep characteristics predicted physical activity the following day.

RESULTS

In unadjusted models, greater daily activity counts (B = -0.05, P = 0.005) and more minutes of MVPA (B = -0.03, P = 0.01) were temporally associated with less total sleep time across the week. Greater sleep efficiency was associated with greater daily activity counts (B = 0.37, P = 0.01) and more minutes of MVPA (B = 0.64, P = 0.009) the following day. Less sleep fragmentation was also associated with greater daily activity counts and more MVPA the following day. Findings were similar after adjustment for age, education, body mass index, depressive symptoms, arthritis, and accelerometer wear time.

CONCLUSIONS

Few studies have used objective measures to examine the temporal relationships between physical activity and sleep. Notably, these findings suggest that nightly variations in sleep efficiency influence physical activity the following day. Thus, improving overall sleep quality in addition to reducing nightly fluctuations in sleep may be important for encouraging a physically active lifestyle in older women.

Variability in self-reported normal sleep across the adult age span

OBJECTIVES

Illustrate the importance of examining within- and between-person differences in sleep across the adult age span.

METHOD

Two weeks of sleep diary data were analyzed for 592 normal sleepers ranging in age from 20 to 96 years. Variability in total sleep time (TST), number of nighttime awakenings (NWAK), sleep-onset latency (SOL), and wake-time after sleep onset (WASO) were examined overall and by age, sex, and race utilizing multilevel models and multiple regression.

RESULTS

Night-to-night differences in sleep within the same individual generally exceeded differences between individuals for TST, SOL, and WASO. The amount of intraindividual variability in TST and NWAK decreased with older age. Further, the degree of reduction in variability in TST associated with age depended on sex and race, with young black females showing the greatest variability. In general, females tended to have more intraindividual variability in SOL and NWAK than males, while race differences were complicated by high variability between blacks.

DISCUSSION

To truly assess and understand individual differences in the sleep of older adults, future research needs to take into account night-to-night variability (including what makes sleep vary from one night to the next), in addition to average sleep.

Greater night-to-night variability in sleep discrepancy among older adults with a sleep complaint compared to noncomplaining older adults

Research in younger adults suggests sleep discrepancy (objective/subjective measurement difference) is a consistent pattern that primarily occurs within individuals with insomnia. To examine whether older adults exhibit a similar pattern, this study compared night-to-night inconsistency in sleep discrepancy between older adults with and without sleep complaints. Older adults (N = 103; mean age = 72.81, SD = 7.12) wore an Actiwatch-L® (24 hr per day) and concurrently completed sleep diaries for 14 days. Sleep discrepancy = diary (sleep onset latency [SOL] or wake [time] after sleep onset [WASO]) - actigraphy (SOL or WASO). Both groups exhibited sleep discrepancy, but complainers exhibited significantly more night-to-night variability. Sleep discrepancy was a variable behavior that was not limited to insomnia, but instead manifested by degree throughout our older sample. Greater attention to variability in sleep research and clinical practice is warranted.

Objective vs. subjective measurements of sleep in depressed insomniacs: first night effect or reverse first night effect?

STUDY OBJECTIVES

This study examined changes in sleep parameters between the laboratory and the home setting before and after laboratory monitoring in depressed insomniacs undergoing treatment.

METHODS

This study was a post hoc analysis of a double-blind, randomized, placebo-controlled clinical trial performed with 60 depressed, insomniac outpatients. Patients underwent actigraphic monitoring along with sleep diaries over a continuous 2-week period. After one week of baseline monitoring, subjects spent one night in the laboratory with concurrent actigraphic and PSG monitoring with sleep diaries. Actigraphic monitoring and sleep diaries were continued for another week at home, along with initiation of open-label fluoxetine (FLX).

RESULTS

Actigraphically recorded laboratory sleep during the night in the laboratory was found to be improved relative to actigraphically recorded sleep at home, with less wake time and greater sleep time and sleep efficiency occurring in the laboratory. In contrast, sleep diaries indicated a slight worsening of sleep in the laboratory compared to home, with significantly more awakenings in the laboratory compared to the week at home before and after the laboratory night.

CONCLUSIONS

The differences between objective and subjective sleep measurements seen in depressed insomniacs may be influenced by the monitoring setting and measurement modality.

CLINICAL TRIAL INFORMATION

ClinicalTrials.gov Identifier: NCT00247624.

A before and after comparison of the effects of forest walking on the sleep of a community-based sample of people with sleep complaints

BACKGROUND

Sleep disturbance is a major health issue in Japan. This before-after study aimed to evaluate the immediate effects of forest walking in a community-based population with sleep complaints.

METHODS

Participants were 71 healthy volunteers (43 men and 28 women). Two-hour forest-walking sessions were conducted on 8 different weekend days from September through December 2005. Sleep conditions were compared between the nights before and after walking in a forest by self-administered questionnaire and actigraphy data.

RESULTS

Two hours of forest walking improved sleep characteristics; impacting actual sleep time, immobile minutes, self-rated depth of sleep, and sleep quality. Mean actual sleep time estimated by actigraphy on the night after forest walking was 419.8 ± 128.7 (S.D.) minutes whereas that the night before was 365.9 ± 89.4 minutes (n = 42). Forest walking in the afternoon improved actual sleep time and immobile minutes compared with forest walking in the forenoon. Mean actual sleep times did not increase after forenoon walks (n = 26) (the night before and after forenoon walks, 380.0 ± 99.6 and 385.6 ± 101.7 minutes, respectively), whereas afternoon walks (n = 16) increased mean actual sleep times from 342.9 ± 66.2 to 475.4 ± 150.5 minutes. The trend of mean immobile minutes was similar to the abovementioned trend of mean actual sleep times.

CONCLUSIONS

Forest walking improved nocturnal sleep conditions for individuals with sleep complaints, possibly as a result of exercise and emotional improvement. Furthermore, extension of sleep duration was greater after an afternoon walk compared to a forenoon walk. Further study of a forest-walking program in a randomized controlled trial is warranted to clarify its effect on people with insomnia.

Exercise effects on night-to-night fluctuations in self-rated sleep among older adults with sleep complaints

Sleep interventions have rarely explored reductions in night-to-night fluctuations [i.e. intra-individual variability (IIV)] in sleep, despite the negative impacts of such fluctuations on affective states and cognitive and physical symptoms. In a community-based randomized controlled trial we evaluated whether physical exercise reduced IIV in self-rated sleep outcomes among middle-aged and older adults with sleep complaints. Under-active adults 55 years and older (n = 66, 67% women) with mild to moderate sleep complaints were randomized to 12 months of a moderate-intensity endurance exercise (n = 36) or a health education control group (n = 30). Daily sleep logs, Pittsburgh Sleep Quality Index (PSQI) and in-home polysomnographic sleep recordings (PSG) were collected at baseline, 6 months and 12 months. Sleep log-derived means and IIV were computed for sleep-onset latency (SOL), time in bed, feeling rested in the morning, number of nighttime awakenings, and wake after final awakening (WAFA). Using intent-to-treat methods, at 6 months no differences in IIV were observed by group. At 12 months, SOL-based IIV was reduced in the exercise group compared with the control (difference = 23.11, 95% CI: 3.04-47.18, P = 0.025, Cohen's d = 0.57). This change occurred without mean-level or IIV changes in sleep-wake schedules. For all sleep variables, except SOL and WAFA, IIV changes and mean-level changes in each variable were negatively correlated (r = -0.312 to -0.691, P < 0.05). Sleep log-derived IIV changes were modestly correlated with mean-level PSQI and PSG-based changes at 12 months. Twelve months of moderate-intensity exercise reduced night-to-night fluctuations in self-rated time to fall asleep, and this relationship was independent of mean-level time to fall asleep.

Nighttime Variability in Wrist Actigraphy

Wrist actigraphy measures sleep activity and circadian rhythm. This study examined nighttime variability in Actiwatch parameters in a sample of breast cancer survivors (BCSs) to determine a minimum number of nights needed to obtain an accurate picture of objective sleep. A descriptive, quantitative, and repeated measures design was used. Consenting participants wore an actigraph and completed a sleep diary across 7 nights. There were no significant differences in wake after sleep onset (WASO), total sleep time (TST), sleep latency, or sleep disturbances across nights of week (Monday to Sunday) or monitoring nights (1st to 7th). Sleep efficiency was significantly better at Night 6 compared with Night 7. The coefficients of variation (CVs) for WASO ranged from 46% to 86%, TST 23%–34%, sleep latency 154%–246%, sleep efficiency 12%–22%, and sleep disturbances 33%–41%. Although the CVs indicated high variability across women, there was little internight variability in WASO or TST during across 7 nights of sleep. This suggests that in BCSs, Actiwatch data could be collected and evaluated from any single night for an accurate measure of usual sleep.

Sleep variability, health-related practices, and inflammatory markers in a community dwelling sample of older adults

OBJECTIVE

To explore relationships between wake- and sleep-related health behaviors and circulating concentrations of inflammatory markers (interleukin [IL]-6 and tumor necrosis factor [TNF]-α) in a cohort of community dwelling older adults. Low-grade chronic inflammation is an important risk factor for age-related morbidity. Health behaviors, including average aggregate measures of sleep, have been linked to increased inflammation in older adults. Variability in sleep timing may also be associated with increased inflammation.

METHOD

Participants were community dwelling older adults ≥ 60 years (n = 222: 39 bereaved, 55 caregivers, 52 with insomnia, and 76 good sleepers). Mean values and intraindividual variability in sleep, as well as caffeine and alcohol use, exercise, and daytime napping, were assessed by sleep diaries. Blood samples were obtained in the morning.

RESULTS

Several interactions were noted between sleep behaviors, inflammatory markers, and participant group. Greater variability in wake time and time in bed was associated with higher IL-6 among good sleepers relative to caregivers and older adults with insomnia. Good sleepers who consumed moderate amounts of alcohol had the lowest concentrations of IL-6 compared with the other three groups who consumed alcohol. Insomnia subjects, but not good sleepers, showed increased concentrations of IL-6 associated with caffeine use. Caregivers showed increased concentrations of TNF-α with alcohol use relative to good sleepers. Greater variability in bedtime, later wake times, and longer time in bed was associated with higher TNF-α regardless of group.

CONCLUSIONS

Moderation and regularity in the practice of certain health behaviors, including sleep practices, were associated with lower plasma levels of inflammatory markers in older adults. Life circumstances and specific sleep disorders may modify these associations.

Intra-individual variability in sleep duration and fragmentation: associations with stress

Despite growing evidence that there is substantial nightly, intra-individual variability in sleep duration and fragmentation, few studies have investigated the correlates of such variability. The current study examined whether intra-individual variability in sleep parameters was associated with psychosocial and physiological indices of stress, especially among those high in negative affect. Participants were 184 adults aged 46-78 (53% men and 41% Black) in the Pittsburgh SleepSCORE study. Wrist actigraphy was used to estimate sleep duration and fragmentation for nine nights, and overnight samples of urinary norepinephrine were collected for two nights. Stressful life events, depression, and anxiety were also reported. Intra-individual differences exceeded between-person differences in actigraphy-measured sleep duration and fragmentation. Stressful life events were associated with increased nightly variability in duration and fragmentation (ps<.05). Negative affect moderated associations between norepinephrine and variability in sleep, such that the greatest variability in actigraphy measures was among those with both high norepinephrine levels and high negative affect (ps<.05). These data suggest that both psychosocial and physiological stress are related to increased nightly variability in individuals' sleep duration and fragmentation, particularly among those reporting negative emotions. These results may have implications for both sleep and health research.

Actigraphy in older adults: comparison of means and variability of three different aggregates of measurement

Actigraphy has emerged as a valuable method for measuring natural sleep patterns; however, it is unclear how many consecutive nights should be measured and what sleep parameter values are typical of older adults. This study examined sleep in relatively healthy community-based older adults for 14 consecutive days. The findings present comparison values for Actiwatch-L actigraphy in older adults, and can be used to determine an appropriate length of measurement. When using means of the aggregate period, a 3-day aggregate is comparable to the values obtained over 7- or 14-day aggregates. However, if variability of the sleep parameter is of interest, a minimum of a 7-day aggregate is needed, and 14-day aggregates are better when measuring sleep onset latency.

Improving actigraphic sleep estimates in insomnia and dementia: how many nights?

In order to investigate how the duration of actigraphic recordings affects the reliability of actigraphic estimates of sleep and 24-h activity rhythm variables, two to 3 weeks of actigraphy were recorded, from which pairs of variables derived from two periods of increasing length (1-10 days) were compared. Two groups were studied: (1) 10 subjects suffering from primary insomnia; and (2) 12 demented elderly subjects living semi-independently in group care facilities of homes for the elderly. Actigraphic estimates of primary measures of sleep (duration and efficiency) and of the 24-h activity pattern (interdaily stability, intradaily variability and amplitude) were calculated on variable lengths of the actigraphic recordings. The average absolute difference of two estimates decreased - and reliability increased - strongly with an increasing number of days analysed. An acceptable reliability of the interdaily stability estimate required more than 7 days of recording. It can be concluded that a valuable improvement in the reliability of actigraphic sleep estimates can be obtained by simply increasing the number of recording nights. The results support the importance of day-to-day variability in insomnia and dementia that has already been previously noted by others, and even suggest the presence of 'week-to-week' variability. This variability may have been involved in the equivocal results of treatment studies in insomnia and dementia where outcome measures were based on a limited number of nights. Such studies could profit from extension of the recording duration to, e.g. 2 weeks, and from the inclusion of variability measures as measures of clinical interest.

Different effects of ambulatory blood pressure monitoring on subjective and objective sleep quality

OBJECTIVE

To determine whether ambulatory blood pressure monitoring affects objective and subjective sleep quality in patients tested at home.

METHODS

Seventy consecutive patients (40 women and 30 men, aged 53+/-15 years), having ambulatory blood pressure monitoring to monitor the efficacy of antihypertensive treatment or to distinguish between hypertension or white-coat hypertension had an evaluation of their sleep quality on a first night with ambulatory blood pressure monitoring and the three following nights without ambulatory blood pressure monitoring. Ambulatory blood pressure monitoring was performed with an auscultatory device with a measure every 15 min during 24 h. Sleep evaluation criteria were both subjective (sleep quality score and sleep questionnaire) and objective (wrist actigraphy monitoring). Sleep parameters during night 1 with ambulatory blood pressure monitoring were compared with those during night 4 without ambulatory blood pressure monitoring. Usual quality of sleep of the patients was assessed by the mean sleep quality score over 7 consecutive days.

RESULTS

The sleep quality score was significantly higher for night 4 than for night 1 (7.3+/-2.1 vs. 5.3+/-2.3; P<0.0001). In contrast, actigraphy parameters (actual sleep time, mean activity score, and fragmentation index) were similar on night 1 and night 4 (6.7+/-1.2 vs. 6.9+/-1.2, 13.2+/-9.8 vs. 12.1+/-8.4, and 31.0+/-14.5 vs. 29.9+/-14.3, respectively). Subjective sleep quality was significantly altered by ambulatory blood pressure monitoring in good sleepers (mean sleep quality score > or =7, 73% of patients) but not in poor sleepers. The effect of ambulatory blood pressure monitoring on subjective sleep quality did not differ between dippers and nondippers.

CONCLUSIONS

Objective sleep quality as assessed by wrist actigraphy is not significantly altered by ambulatory blood pressure monitoring, whereas subjective sleep quality is adversely affected in good sleepers.

Sleep studies: which technologies?

The demand for sleep services for young patients has escalated due to the increased recognition of pediatric sleep disorders over the past two decades. In this overview, we will highlight the essentials of pediatric sleep monitoring and stress particular issues that require the awareness of clinicians evaluating children for sleep disorders. While many techniques used in the "adult" sleep centers may suffice for the older adolescent patient, specific tailoring of the design of the sleep center to younger children and their families, and attention to the age-sensitive components of sleep data acquisition and interpretation are increasingly important in younger children. Several promising newer technologies and their potential for future clinical utility will be also reviewed.

Actigraphic investigations on the activity-rest behavior of right- and left-handed students

The aim of this study was to explore differences between left-and right-handed subjects in sleep duration. Sleep and activity patterns were continuously registered for 12 days using actometers on 20 left-handed and 20 right-handed medical students in Berlin. Handedness was determined by a modified version of the Edinburgh handedness inventory. Each participant wore one actometer on each wrist. Actiwatch Sleep Analysis Software (CNT, UK) was used to evaluate the data, and statistical calculations were performed with a non-parametric variance analysis. A significant difference in mean sleep duration between left-handers (7.9 h) and right-handers (7.3 h) was determined (p=0.025 for measurement made on the dominant hand and p=0.013 for ones made on the non-dominant hand). In contrast, the maximal phase of daily activity (acrophase) did not show any difference between the two groups. The difference in sleep duration might be caused by either the greater effort required for left-handers to cope in a right-handed world or by structural brain differences.

Factors associated with objective (actigraphic) and subjective sleep quality in young adult women

OBJECTIVE

The aim of this study was to describe factors associated with actigraphic and subjective sleep quality in young women.

METHODS

Participants were 73 regularly menstruating women, 20-40 years old, who were not taking oral contraceptives, pregnant, or shift workers. Women contributed an average of 7 nights of actigraphy data during the luteal menstrual cycle phase, resulting in a total of 595 nights of data.

RESULTS

One night of actigraphy data was unreliable for measuring total sleep time, sleep onset, and time in bed (intraclass correlation < or =.15) but was acceptable for measuring sleep efficiency and total wake time (intraclass correlation [ICC]=.52). Going to bed late, medication use, employment, increased daylight hours, longer menstrual cycle length, and higher body mass index (BMI) were associated with poorer actigraphic sleep measures. Employment, age, and perceived stress were associated with subjective sleep quality.

CONCLUSION

Multiple factors were associated with sleep quality in these young women who were sleeping at home. However, the associations differed for subjectively versus actigraphically assessed sleep quality. Actigraphy is feasible for measuring sleep, but multiple recording nights may be needed to obtain reliable estimates.

The role of actigraphy in sleep medicine

During the last decade actigraphy (activity-based monitoring) has become an essential tool in sleep research and sleep medicine. The validity, reliability and limitations of actigraphy for documenting sleep-wake patterns have been addressed. Normative data on sleep-wake patterns across development have been collected. Multiple studies have documented the adequacy of actigraphy to distinguish between clinical groups and to identify certain sleep-wake disorders. Actigraphy has also been shown to be effective in documenting the effects of various behavioral and medical interventions on sleep-wake patterns. Actigraphy is less useful for documenting sleep-wake in individuals who have long motionless periods of wakefulness (e.g. insomnia patients) or who have disorders that involve altered motility patterns (e.g. sleep apnea). Potential users should be aware of a number of pitfalls of actigraphy: (1) validity has not been established for all scoring algorithms or devices, or for all clinical groups; (2) actigraphy is not sufficient for diagnosis of sleep disorders in individuals with motor disorders or high motility during sleep; (3) the use of computer scoring algorithms without controlling for potential artifacts can lead to inaccurate and misleading results.

Changes in EEG power density during sleep laboratory adaptation in depressed inpatients

BACKGROUND

The aim of the present study was to evaluate the first-night effect in depressed inpatients, using standard sleep measures as well as all-night spectral analysis of the sleep electroencephalogram (EEG).

METHODS

Eighteen drug-free, depressed inpatients were studied for 3 consecutive nights in the hospital sleep laboratory.

RESULTS

Visual sleep scoring results showed a slight but measurable first-night effect, characterized by a reduction of rapid eye movement (REM) sleep amount and increased wakefulness. Sleep EEG spectral analysis showed significantly reduced delta (p <.01) and theta (p <.05) power density in non-REM (NREM) sleep of the first night compared with that of the second and third nights. These differences were limited to the early part of the sleep period, a time during the night that is particularly vulnerable to the effects of depressive disorder. In contrast to the NREM sleep findings, spectral REM variables studied did not significantly vary across the three nights.

CONCLUSIONS

The results obtained suggest that first-night data should not be simply discarded but could be used in subsequent analyses and could be considered useful in the evaluation of the sleep of depressed patients.

Effects of morning bright light in healthy elderly women: effects on wrist activity

To investigate the effects of 8000 lux morning bright light in the elderly, home-based motor activity on sleep was monitored for 5 days in 10 healthy women (mean age: 59.7 years old, range: 50-69 years old). The activity level and movement index on night 4 were significantly lower in bright light conditions, compared with the controlled condition. The activity level during the day was not significantly different between the two conditions. These results indicate that 8000 lux morning bright light improves sleep quality in healthy elderly women.

Assessment of bed temperature monitoring for detecting body movement during sleep: comparison with simultaneous video image recording and actigraphy

This study was designed to assess changes in bed temperature as an index of body movement. Changes in the temperature of the bed or mattress were used to estimate motility and number of awakenings, and total time in bed. Simultaneous temperature records, video image recordings and actigraphic data were obtained from 12 young adults for three consecutive nights. Significant agreement of time in bed and body movement among the three measurements was found. Intra-individual variability was low for time in bed. In a second study, 10 healthy elderly subjects used a temperature monitor at home for four consecutive nights. The time in bed was 8.1 h, a little longer than for the younger adults, but not markedly different. These studies show the potential usefulness of bed temperature monitoring as an index of sleep behaviour. Although the precise sleep index could not be observed, behaviour could be evaluated simply.

Reproducibility of oximetry with a static charge-sensitive bed in evaluation of obstructive sleep apnoea

The reproducibility of overnight polygraphic recording with oximetry, the use of a static charge-sensitive bed (SCSB), thermistors and a body position sensor was assessed in diagnosing obstructive sleep apnoea syndrome (OSAS). Forty-six patients with a clinical suspicion of OSAS underwent a repeat recording. No treatment for OSAS and no change in patient characteristics was allowed between duplicate nights. Between repeated recordings significant correlations were found for ODI4, time spent at SaO2 < 90% and the mean nadir SaO2. Good agreement was found in concordance of classification of ODI4, time spent at SaO2 < 90% and body movements. The combination of oximetry, thermistors, SCSB and body position sensor has a good reproducibility as an affordable screening method in the evaluation of OSAS.

Gender differences in self-evaluated sleep quality and activity of middle-aged and aged subjects

In order to investigate the gender difference of sleep and activity in middle-aged and aged individuals, home-based sleep was self-evaluated for sleep quality and activity for 5 nights in 20 healthy adults (50-76 years old; 11 women, nine men). There was no significant gender difference for subjective sleep quality. However, the activity level and movement index at night were significantly higher in men than in women, and the activity level during the day was significantly lower in men than in women. The objective sleep quality of men was significantly worse than that of women, however, subjective sleep quality does not differ.

Spontaneous movements during sleep in children: temporal organization and changes with age

Developmental changes in the temporal organization of spontaneous movements during sleep was studied in children between 9 months and 11 years of age. Subjects were monitored in the home environment for the entire sleep period using actigraphy and videography. Rhythmicity in sleep-related spontaneous movements was examined using FFT and chi-square periodogram time series analyses. A dominant periodicity of 60-120 minutes was identified which was found to progressively lengthen with age. A microanalysis of the temporal structure of movements revealed a developmental decline in bout duration, but a paradoxical increase in bout frequency. These results show that motor activity becomes less robust and more fragmented as development progresses while retaining underlying rhythmic integrity, and argue for the dynamic influence of CNS maturation on the organization and expression of sleep-related spontaneous movements.

Ambulatory monitoring devices and the forensic autopsy

Ambulatory monitoring devices (AMDs) such as Holter (ECG) and apnea (respiratory) monitors with built-in date- and time-correlated memories are occasionally encountered in the forensic autopsy. Diagnostic data are usually readily obtained by returning the device to the hospital department or rental company. This data can be easily correlated with autopsy findings to arrive at surprisingly precise conclusions in some cases. We present two illustrative cases: an elderly man wearing a Holter monitor who shot himself in the mouth with a shotgun, and a 15-month-old oxygen-dependent prematurely born boy with bronchopulmonary dysplasia whose apnea monitor had been turned off 5 days before he died of bronchopneumonia. We discuss other kinds of AMDs that may be encountered in the forensic autopsy and suggest that information from these monitors perhaps should become part of the forensic autopsy report.

Circadian distribution of motor activity and immobility in narcolepsy: assessment with continuous motor activity monitoring

The circadian distribution of motor activity and immobility of 14 unmedicated narcoleptics and matched controls was evaluated by monitoring continuous wrist motor activity 5 successive days and nights at home. Sleep was also assessed by sleep logs. The amplitude of the circadian rhythm of motor activity and immobility was significantly lower in narcoleptics than in controls. The variables that best distinguish narcoleptics from controls were the diurnal and nocturnal mean duration of uninterrupted immobility, which can be explained by excessive daytime sleepiness and frequent nocturnal awakenings, respectively. Thus, measures of diurnal and nocturnal motor activity and immobility appear useful for the objective assessment of some of the sleep-wakefulness manifestations of narcolepsy.

Wrist actigraphic assessment of sleep in 116 community based subjects suspected of obstructive sleep apnoea syndrome

BACKGROUND

The combined use of wrist actigraphic assessment and self assessment of sleep in the screening of obstructive sleep apnoea syndrome was evaluated in a community based sample.

METHODS

One hundred and sixteen community based subjects clinically suspected of having obstructive sleep apnoea (syndrome) were evaluated by means of simultaneous ambulatory recording of respiration (oronasal flow thermistry), motor activity (wrist actigraphy), and subjective sleep (sleep log) during one night of sleep.

RESULTS

The subjects were distributed according to their apnoea index (AI); AI < 1 (non-apnoeic snorers) 44%; AI 1- < 5 39%; and AI > or = 5 17%. High apnoea index values were associated with self reported disturbed sleep initiation and more fragmented and increased levels of motor activity and decreased duration of immobility periods, particularly in those with an apnoea index of > or = 5. Across subjects the duration of immobility periods was the only predictor of the apnoea index, explaining 11% of its variance. Use of the multiple regression equation to discriminate retrospectively between those with an apnoea index of < 1 and > or = 5 resulted in sensitivity and specificity values of 75% and 43%, and 5% and 100%, respectively.

CONCLUSIONS

The combined use of a sleep log and actigraphic assessment of sleep failed to identify reliably those subjects who suffered from obstructive sleep apnoea (syndrome) in a sample of community based subjects reporting habitual snoring combined with excessive daytime sleepiness and/or nocturnal respiratory arrests.