Objective assessment of sleep and sleep problems in older adults with intellectual disabilities

Little is known about sleep in older adults with intellectual disability (ID). Aim of this study was to investigate sleep and its associated factors, and to estimate the prevalence of sleep problems in this population. This study was part of the healthy aging and intellectual disabilities study. Sleep was assessed using the Actiwatch, a watch-like device that measures sleep and wakefulness based on movement activity. Participants (n = 551) wore the Actiwatch at least seven days and nights continuously. Variables of interest were time in bed (TIB), sleep onset latency, total sleep time, wake after sleep onset, sleep efficiency and get-up time latency. Multivariate analyses were used to investigate factors associated with these sleep parameters. Provisional definitions were drafted to estimate the prevalence of sleep problems. Mean TIB was 630 min. Longer TIB was independently associated with higher age, more severe level of ID, living at a central facility, wheelchair dependence, female gender and depressive symptoms (adjusted R² = .358, F-change = 8.302, p < .001). The prevalence of sleep problems was 23.9% settling problem, 63.1% night waking problem, 20.9% short sleep time, 9.3% early waking problem. 72% of the participants had at least one problem, 12.3% had three or more sleep problems. Older adults with ID lie in bed very long, and the prevalence of sleep problems is high. Further research should focus on causality of the relationships found in this study, and effects of sleep problems on health and well-being in this population.     

Wake detection capacity of actigraphy during sleep

STUDY OBJECTIVES: To evaluate the ability of actigraphy compared to polysomnography (PSG) to detect wakefulness in subjects submitted to 3 sleep conditions with different amounts of wakefulness: a nocturnal sleep episode and 2 daytime recovery sleep episodes, one with placebo and one with caffeine. A second objective was to compare the ability of 4 different scoring algorithms (2 threshold algorithms and 2 regression analysis algorithms) to detect wake in the 3 sleep conditions. DESIGN: Three nights of simultaneous actigraphy (Actiwatch-L, Mini-Mitter/Respironics) and PSG recordings in a within-subject design. SETTING: Chronobiology laboratory. PARTICIPANTS: Fifteen healthy subjects aged between 20 and 60 years (7M, 8F). INTERVENTIONS: 200 mg of caffeine and daytime recovery sleep. RESULTS: An epoch-by-epoch comparison between actigraphy and PSG showed a significant decrease in actigraphy accuracy with increased wakefulness in sleep conditions due to the low sleep specificity of actigraphy (generally <50%). Actigraphy overestimated total sleep time and sleep efficiency more strongly in conditions involving more wakefulness. Compared to the 2 regression algorithms, the 2 threshold algorithms were less able to detect wake when the sleep episode involved more wakefulness, and they tended to alternate more between wake and sleep in the scoring of long periods of wakefulness resulting in an overestimation of the number of awakenings. CONCLUSION: The very low ability of actigraphy to detect wakefulness casts doubt on its validity to measure sleep quality in clinical populations with fragmented sleep or in situations where the sleep-wake cycle is challenged, such as jet lag and shift work.     

Non-constraining sleep/wake monitoring system using bed actigraphy

This paper introduces a new method, bed actigraphy (BACT) for user-friendly sleep-wake monitoring. BACT provides a non-intrusive acquisition of activity data, and in particular does not require that sensors be attached to the subject’s body. The system consists of four load-sensing cells supporting the bed, an A/D converter, and a microcontroller with appropriate software. The performance of BACT was compared to that of standard polysomnography (PSG) recordings and wrist-worn actigraphy (ACT). Ten normal volunteers underwent overnight PSG recordings and were examined simultaneously with BACT and ACT. An automatic scoring algorithm scored each 30-s epoch of the BACT recordings for either ‘Wake’ or ‘Sleep.’ A sleep specialist manually scored the PSG recordings, and the results were divided into ‘Wake’ and ‘Sleep’ categories. The three methods showed a significant correlation when compared with in the contingency test. The mean epoch-by-epoch agreements between the BACT and PSG, ACT and PSG, and BACT and ACT recordings were 95.2, 92.9, and 94.3%, respectively. The mean absolute differences in sleep percentage (SP) between them were 1.8 ± 0.82, 3.4 ± 1.45, and 1.9 ± 1.16 %, respectively. BACT differentiation of the ‘Wake’ and ‘Sleep’ stages proved to be sufficiently robust, and its results were comparable to PSG analysis. This finding supports the experimental and clinical value of bed-activity monitoring during sleep.     

‘Maths on the move’: Effectiveness of physically-active lessons for learning maths and increasing physical activity in primary school students

ObjectivesThis study evaluated the benefit of physically-active lessons for learning maths multiplication-tables. The impact of the intervention on general numeracy, physical activity (PA), aerobic fitness, body mass index (BMI) and school-day moderate to vigorous PA (MVPA) was also assessed.DesignRandomised controlled cross-over trial.MethodYear 3 students (n = 172, mean age 8.4 ± 0.3 years, 48% male) were recruited from 10 classes across two urban primary schools. Participants were randomly assigned to a seated classroom (Classroom) group or physically-active lessons in the playground (Playground) and crossed over to the alternative condition in the subsequent school term. The 6-week intervention comprised 3 × 30 min sessions/week. Multiplication-tables (teacher-designed test) and general maths (standardised test) were assessed pre- and post-intervention. Aerobic fitness was assessed via the shuttle-run. Pre- to post-intervention change scores were compared for analysis and effect sizes (ES) calculated. Total PA and MVPA were assessed with accelerometers in a subset of participants.ResultsMultiplication scores improved significantly more in Playground than Classroom groups (ES = 0.23; p = 0.045), while no significant differences were observed in general numeracy (ES = 0.05; p = 0.66). Total PA and MVPA were substantially higher during Playground than Classroom lessons (ES: total PA = 7.4, MVPA = 6.5; p < 0.001) but there were no differences in PA/MVPA between the groups throughout the rest of the school day. Aerobic fitness improved more in Playground than Classroom groups (ES = 0.3; p < 0.001) while the change in BMI was not different between groups (p = 0.39).ConclusionsPhysically-active lessons may benefit the learning of maths multiplication-tables while favourably contributing to school-day PA/MVPA.     

Associations of self-reported and actigraphy-assessed sleep characteristics with body mass index and waist circumference in adults: moderation by gender

ObjectivesSelf-reported sleep duration has been linked to body mass index (BMI) and waist circumference in previous work; however, data regarding if these associations are stronger in men or women have been mixed, and few studies have objectively measured sleep. We investigated self-reported and actigraphy-assessed sleep characteristics in relation to BMI and waist circumference and examined the extent to which these associations differ by gender.DesignArchived cross-sectional data collected from 2004 to 2006 from the National Survey of Midlife Development in the United States (MIDUS) Biomarkers Study were used. Participants included 1248 adults (43% men) who reported their habitual sleep duration, and a subset of participants (N = 441; 40% men) who underwent seven nights of wrist actigraphy.ResultsSelf-reported total sleep time (TST), actigraphy-assessed TST, and actigraphy-assessed sleep efficiency (SE) were inversely associated with BMI in the full sample of both men and women. Gender moderated associations between actigraphy assessments of sleep and anthropometric variables; however, TST and SE were related to BMI and waist circumference in women only. Associations between sleep and waist circumference were independent of BMI.ConclusionsSleep duration and sleep continuity are associated with body weight and distribution of body fat, but these associations were stronger or were only present in women.     

Automatic detection of wakefulness and rest intervals in actigraphic signals: A data-driven approach

Actigraphy is an useful tool for evaluating the activity pattern of a subject; activity registries are usually processed by first splitting the signal into its wakefulness and rest intervals and then analyzing each one in isolation. Consequently, a preprocessing stage for such a splitting is needed. Several methods have been reported to this end but they rely on parameters and thresholds which are manually set based on previous knowledge of the signals or learned from training. This compromises the general applicability of this methods. In this paper we propose a new method in which thresholds are automatically set based solely on the specific registry to be analyzed. The method consists of two stages: (1) estimation of an initial classification mask by means of the expectation maximization algorithm and (2) estimation of a final refined mask through an iterative method which re-estimates both the mask and the classifier parameters at each iteration step. Results on real data show that our methodology outperforms those so far proposed and can be more effectively used to obtain derived sleep quality parameters from actigraphy registries.     

Variation of circadian activity rhythm according to body mass index in children

Background/objectivesThis study aimed to examine the variations of circadian activity rhythm of children according to objective body mass index (BMI) values, using a novel statistical framework (ie, Functional Linear Modeling, FLM), separately for school- and weekend days.MethodsA total of 107 participants (60 females; mean age: 10.25 ± 0.48 years) wore an actigraph for seven days during a regular school-week. While valid actigraphic data during school days were available for each of these children, this number decreased to 53 (31 females; mean age: 10.28 ± 0.51 years) during weekend days.ResultsExamining the school days, significantly higher motor activity in participants with higher BMI was observed from around 4:00 a.m. to 6:00 a.m., with a peak about 5:00 a.m. On the contrary, applying the FLM to the weekend days actigraphic data, no significantly different variation of circadian activity rhythm was observed, according to BMI.ConclusionsIn this specific sample of children, during school days, higher BMI is associated with higher activity level in a specific time window in the second half of nocturnal sleep. The lack of significant findings during weekend days could be explained because of higher variability of get-up time and/or the reduced sample size. Future longitudinal studies could explore if the higher motor activity in that specific time window qualifies as a predictive marker of the development of overweight and obesity. If so, early preventive strategies directed towards those at higher risk could be effectively implemented.