Actigraphically recorded motor activity and immobility across sleep cycles and stages in healthy male subjects

The aim of this study was to compare the extent to which activity and immobility measures are related to sleep stages and sleep cycles in order to improve the informative value of actigraphic assessment of sleep. We therefore performed simultaneous ambulatory polysomnography and wrist-activity monitoring (AM) in 14 healthy male subjects without sleep complaints. In this context, a simple method for transforming raw motor activity data into a time-series reflecting onset and duration of activity and immobility clusters is introduced. Our results demonstrate that nocturnal AM measures were significantly affected by sleep stage. Low activity levels and particularly prolonged episodes of uninterrupted immobility were associated with increasing sleep depth. On the other hand, high activity levels and prolonged episodes of activity were related to intermittent wakefulness during sleep. Our results suggest that measures reflecting the occurrence and duration of activity and immobility clusters provide a better approach in studying the relationship between activity/immobility and sleep stages. Except for the duration of uninterrupted immobility episodes, which showed a significant decrease in the fourth cycle, none of the AM measures showed a significant cycle-to-cycle variation. Consequently, mean nocturnal motor activity measures provide an accurate reflection of the total sleep period. However, none of the AM-derived measures seems useful in evaluating the cycle structure during sleep.     

Melatonin and bright-light treatment for rest-activity disruption in institutionalized patients with Alzheimer's disease

OBJECTIVES: To test whether the addition of melatonin to bright-light therapy enhances the efficacy in treating rest–activity (circadian) disruption in institutionalized patients with Alzheimer's disease (AD).
DESIGN: Randomized, controlled trial.
SETTING: Two nursing homes in San Francisco, California.
PARTICIPANTS: Fifty subjects (mean age 86) with AD.
INTERVENTION: Experimental subjects received 1 hour of morning light exposure (≥2,500 lux in gaze direction) Monday to Friday for 10 weeks and 5 mg melatonin (LM, n=16) or placebo (LP, n=17) in the evening. Control subjects (n=17) received usual indoor light (150–200 lux).
MEASUREMENTS: Nighttime sleep variables, day sleep time, day activity, day:night sleep ratio, and rest–activity parameters were determined using actigraphy.
RESULTS: Linear mixed models were employed to test the primary study hypotheses. No significant differences in nighttime sleep variables were found between groups. At the end of the intervention, the LM group showed significant improvement in daytime somnolence as indicated by a reduction in the duration of daytime sleep, an increase in daytime activity, and an improvement in day:night sleep ratio. The LM group also evidenced a significant increase in rest–activity rhythm amplitude and goodness of fit to the cosinor model.
CONCLUSION: Light treatment alone did not improve nighttime sleep, daytime wake, or rest–activity rhythm. Light treatment plus melatonin increased daytime wake time and activity levels and strengthened the rest–activity rhythm. Future studies should resolve the question of whether these improvements can be attributed to melatonin or whether the two zeitgebers interact to amplify efficacy.     

Estimating sleep from multisensory armband measurements: validity and reliability in teens

Given the recognition that sleep may influence obesity risk, there is increasing interest in measuring sleep parameters within obesity studies. The goal of the current analyses was to determine whether the SenseWear^® Pro3 Armband (armband), typically used to assess physical activity, is reliable at assessing sleep parameters. The armband was compared with the AMI Motionlogger^® (actigraph), a validated activity monitor for sleep assessment, and with polysomnography, the gold standard for assessing sleep. Participants were 20 adolescents (mean age = 15.5 years) with a mean body mass index percentile of 63.7. All participants wore the armband and actigraph on their non‐dominant arm while in‐lab during a nocturnal polysomnographic recording (600 min). Epoch‐by‐epoch sleep/wake data and concordance of sleep parameters were examined. No significant sleep parameter differences were found between the armband and polysomnography; the actigraph tended to overestimate sleep and underestimate wake compared with polysomnography. Both devices showed high sleep sensitivity, but lower wake detection rates. Bland–Altman plots showed large individual differences in armband sleep parameter concordance rates. The armband did well estimating sleep overall, with group results more similar to polysomnography than the actigraph; however, the armband was less accurate at an individual level than the actigraph.     

Melatonin effects on sleep, mood, and cognition in elderly with mild cognitive impairment

Abstract: The effects of immediate-release melatonin on circadian rest-activity profiles, cognition, and mood were investigated in ten elderly individuals with self-reported sleep-wake disturbances. Melatonin (6 mg), administered 2 hr before habitual bedtime, enhanced the rest-activity rhythm and improved sleep quality as observed in a reduction in sleep onset latency and in the number of transitions from sleep to wakefulness. However, total sleep time was not significantly increased nor was wake within sleep significantly reduced. The ability to remember previously learned items improved along with a significant reduction in depressed moods. No side effects or contraindications were reported by any of our participants during the 10 day trials. These data suggest that melatonin can safely improve some aspects of sleep, memory, and mood in the elderly in short-term use.     

Circadian urinary 6-sulphatoxymelatonin, cortisol excretion and locomotor activity in airline pilots during transmeridian flights

Airline pilots divided into two groups of age (over and under 50 years) were studied before, during and after westbound (Madrid-Mexico City-Madrid, n = 12) and eastbound (Madrid-Tokyo-Madrid, n = 21) flights. A group of 10 age-matched people staying in Madrid were submitted to the same tests and served as a control group. Changes in urinary 6-sulphatoxymelatonin (6-aMTs) and free cortisol excretion (determined in 6-hr intervals) were measured by radioimmunoassay. Using wrist actigraphy, the circadian locomotor activity rhythm (LAR) was also monitored. Maximal baseline excretion of 6-aMTs occurred between 00:00 and 12:00 hr and maximal excretion of cortisol took place between 6:00 and 12:00 hr in the control group. Analysed globally, older pilots exhibited significantly lower values of 6-aMTs than younger ones. In both flight directions, pilots maintained the pattern of excretion of 6-aMTs, corresponding to baseline. The return flight to Madrid from Mexico and Tokyo coincided with a maximum in 6-aMTs excretion. Pilots kept the cortisol pattern found in the control group, with those over 50 years of age exhibiting significantly lower cortisol values than the younger ones. A 7-hr delay in acrophase of LAR after 2 days in Mexico City was found after cosinor analysis, and similar pre-flight values were found after returning to Madrid. An 8-9-hr acrophase advance of LAR was observed after arriving in Tokyo, with acrophase on the post-return flight day still being advanced 3 4 hr as compared to pre-flight values. Decreases in the amplitude of LAR in older pilots were found at Mexico City, as well as at Tokyo stopover and on post-flight day. Data confirm the occurrence of internal desynchronization in airline crewmembers after transmeridian flights.     

Parasympathetic nervous system activity and children's sleep

We examined indices of children's parasympathetic nervous system activity (PNS), including respiratory sinus arrhythmia during baseline (RSAB) and RSA reactivity (RSAR), to a laboratory challenge, and importantly the interaction between RSAB and RSAR as predictors of multiple parameters of children's sleep. Lower RSAR denotes increased vagal withdrawal (reductions in RSA between baseline and task) and higher RSAR represents decreased vagal withdrawal or augmentation (increases in RSA between baseline and task). A community sample of school‐attending children (121 boys and 103 girls) participated [mean age = 10.41 years; standard deviation (SD) = 0.67]. Children's sleep parameters were examined through actigraphy for 7 consecutive nights. Findings demonstrate that RSAB and RSAR interact to predict multiple sleep quality parameters (activity, minutes awake after sleep onset and long wake episodes). The overall pattern of effects illustrates that children who exhibit more disrupted sleep (increased activity, more minutes awake after sleep onset and more frequent long wake episodes) are those with lower RSAB in conjunction with lower RSAR. This combination of low RSAB and low RSAR probably reflects increased autonomic nervous system arousal, which interferes with sleep. Results illustrate the importance of individual differences in physiological regulation indexed by interactions between PNS baseline activity and PNS reactivity for a better understanding of children's sleep quality.     

Associations of loneliness and social isolation with actigraph and self-reported sleep quality in a national sample of older adults

Study ObjectivesTo examine associations of social isolation and loneliness with sleep in older adults and whether associations differ for survey and actigraph sleep measures.MethodsThis study used data from the National Social Life, Health, and Aging Project (NSHAP), a nationally representative study of community-dwelling older adults born 1920–1947. A random one-third of participants in 2010–2011 were invited to participate in a sleep study (N = 759) that included survey questions, 72 hours of wrist actigraphy, and a sleep log. Perceived loneliness was measured using three questions from the UCLA Loneliness Scale. An index of social isolation was constructed from nine items that queried social network characteristics and social interactions. We used ordinary least squares and ordinal logistic regression to examine whether sleep measures were associated with loneliness and social isolation adjusted for potential sociodemographic confounders.ResultsSocial isolation and loneliness had a low correlation (Spearman’s correlation = 0.20). Both loneliness and social isolation were associated with actigraphy measures of more disrupted sleep: wake after sleep onset and percent sleep. Neither was associated with actigraph total sleep time. Increased loneliness was strongly associated with more insomnia symptoms and with shorter sleep duration assessed by a single question, but social isolation was not. More isolated individuals spent a longer time in bed.ConclusionsWe found that both loneliness and social isolation were associated with worse actigraph sleep quality, but their associations with self-reported sleep differed. Only loneliness was associated with worse and shorter self-reported sleep.