Validity,potential clinical utility,and comparison of consumer and research‐grade activity trackers in Insomnia Disorder I: In‐lab validation against polysomnography

Consumer activity trackers claiming to measure sleep/wake patterns are ubiquitous within clinical and consumer settings. However, validation of these devices in sleep disorder populations are lacking. We examined 1 night of sleep in 42 individuals with insomnia (mean = 49.14 ± 17.54 years) using polysomnography, a wrist actigraph (Actiwatch Spectrum Pro: AWS) and a consumer activity tracker (Fitbit Alta HR: FBA). Epoch‐by‐epoch analysis and Bland?Altman methods evaluated each device against polysomnography for sleep/wake detection, total sleep time, sleep efficiency, wake after sleep onset and sleep latency. FBA sleep stage classification of light sleep (N1 + N2), deep sleep (N3) and rapid eye movement was also compared with polysomnography. Compared with polysomnography, both activity trackers displayed high accuracy (81.12% versus 82.80%, AWS and FBA respectively; ns) and sensitivity (sleep detection; 96.66% versus 96.04%, respectively; ns) but low specificity (wake detection; 39.09% versus 44.76%, respectively; p = .037). Both trackers overestimated total sleep time and sleep efficiency, and underestimated sleep latency and wake after sleep onset. FBA demonstrated sleep stage sensitivity and specificity, respectively, of 79.39% and 58.77% (light), 49.04% and 95.54% (deep), 65.97% and 91.53% (rapid eye movement). Both devices were more accurate in detecting sleep than wake, with equivalent sensitivity, but statistically different specificity. FBA provided equivalent estimates as AWS for all traditional actigraphy sleep parameters. FBA also showed high specificity when identifying N3, and rapid eye movement, though sensitivity was modest. Thus, it underestimates these sleep stages and overestimates light sleep, demonstrating more shallow sleep than actually obtained. Whether FBA could serve as a low‐cost substitute for actigraphy in insomnia requires further investigation.     

The link between maternal sleep and permissive parenting during late adolescence

Utilizing a multi‐method design, the present study examined the association between maternal sleep, assessed via actigraphy and self‐reports, and permissive parenting (e.g. lax, inconsistent discipline) during adolescence, as well as the extent to which this association differed by mothers’ race/ethnicity and socioeconomic status. The sample was comprised of 234 mothers (M age = 41.76 years, SD = 6.25; 67% European‐American, 31% African‐American, 2% other race/ethnicities) and 237 adolescents (113 boys, 124 girls; M age = 15.80 years, SD = 0.80; 66% European‐American, 34% African‐American). Mothers’ sleep duration (actual sleep minutes) and quality (sleep efficiency, latency, long wake episodes) were assessed using actigraphy. Mothers also reported on their sleep problems and adolescents reported on mothers’ permissive parenting behaviours. Results revealed that actigraphy‐based longer sleep duration and shorter sleep latency were associated with lower levels of permissive parenting. Further, mothers’ race/ethnicity and socioeconomic status moderated the association between actigraphy‐based sleep quality (i.e. sleep efficiency, long wake episodes) and permissive parenting. Specifically, a negative association between sleep efficiency and permissive parenting was evident only for African‐American mothers. In addition, a positive association between more frequent night wakings and permissive parenting was evident only for mothers from lower socioeconomic status households. The findings highlight the benefits of longer and higher‐quality sleep for reducing the risk of permissive parenting, especially among ethnic minority mothers and mothers from lower socioeconomic status households.     

Discrepancies in sleep diary and actigraphy assessments in adults with fibromyalgia: Associations with opioid dose and age

Sleep diary and actigraphy assessments of insomnia symptoms in patients with fibromyalgia (FM) are often discrepant. We examined whether opioid dose and age interact in predicting magnitude or direction of discrepancies. Participants (N = 199, M = 51.5 years, SD = 11.7) with FM and insomnia completed 14 days of diaries and actigraphy. Multiple regressions determined whether average opioid dose and its interaction with age predicted magnitude or direction of diary/actigraphy discrepancies in sleep onset latency (SOL), wake after sleep onset (WASO) and sleep efficiency (SE), controlling for sex, use of sleep medication, evening pain and total sleep time. Higher opioid dose predicted greater magnitude of discrepancy in SOL and SE. Opioid dose interacted with age to predict direction but not magnitude of discrepancy in SOL and SE. Specifically, higher opioid use was associated with better subjective (shorter SOL, higher SE) than objective reports of sleep among younger adults, and longer subjective than objectively measured SOL among older adults. Opioid dose did not predict magnitude or direction of WASO discrepancies. In FM, a higher opioid dose increases diary/actigraphy SOL and SE discrepancies, and direction of discrepancies may depend on age. We speculate that increased opioid use combined with age‐related factors, such as slow wave sleep disruption, increased awakenings and/or cognitive decline, may impact perceived sleep.     

Relation between ambulatory actigraphy and laboratory polysomnography in insomnia practice and research

Actigraphy is increasingly used in practice and research studies because of its relative low cost and decreased subject burden. How multiple nights of at‐home actigraphy compare to one independent night of in‐laboratory polysomnography (PSG) has not been examined in people with insomnia. Using event markers (MARK) to set time in bed (TIB) compared to automatic program analysis (AUTO) has not been systematically evaluated. Subjects (n = 30) meeting DSM‐5 criteria for insomnia and in‐laboratory PSG sleep efficiency (SE) of <85% were studied. Subjects were free of psychiatric, sleep or circadian disorders, other chronic conditions and medications that effect sleep. Subjects had an in‐laboratory PSG, then were sent home for 7 nights with Philips Actiwatch Spectrum Plus. Data were analysed using Philips Actiware version 6. Using the mean of seven nights, TIB, total sleep time (TST), SE, sleep‐onset latency (SOL) and wake after sleep onset (WASO) were examined. Compared to PSG, AUTO showed longer TIB and TST and less WASO. MARK only differed from PSG with decreased WASO. Differences between the PSG night and the following night at home were found, with better sleep on the first night home. Actigraphy in people with insomnia over seven nights is a valid indicator of sleep compared to an independent in‐laboratory PSG. Event markers increased the validity of actigraphy, showing no difference in TIB, TST, SE and SOL. AUTO was representative of SE and SOL. Increased SE and TST without increased TIB suggests possible compensatory sleep the first at night home after in‐laboratory PSG.     

Brief school‐based interventions to assist adolescents’ sleep‐onset latency: Comparing mindfulness and constructive worry versus controls

Difficulties falling asleep are common among adolescents, especially during times of stress. Adolescents may thus benefit from brief techniques (15 min) that decrease pre‐sleep cognitive‐emotional arousal and sleep‐onset latency. The present study used a 3 (intervention: mindfulness bodyscan mp3, constructive worry, control) by 3 (time: baseline, week 1, week 2) mixed‐model design on a school‐based sample of adolescents (N = 232; M_age = 15.9 ± 0.8 years, range = 14–18 years; 19% male), and a sub‐sample of adolescents with prolonged sleep‐onset latency (i.e. ≥30 min; N = 119; M_age = 16.9 ± 0.9 years; 21% male). It was expected that the 15‐min pre‐recorded breath‐based mindfulness bodyscan, and constructive worry, would decrease sleep‐onset latency and pre‐sleep arousal similarly over time, relative to the control condition. A significant interaction was observed among adolescents with prolonged sleep‐onset latency, who completed ≥3 days for at least 1 week (p = .001), where mindfulness decreased sleep‐onset latency relative to constructive worry and the control. Neither technique changed pre‐sleep worry or cognitive‐emotional arousal, or associated daytime functioning (both the whole sample and sub‐sample). A pre‐recorded mp3 breath‐based mindfulness bodyscan technique is a promising means by which adolescents with prolonged sleep‐onset latency can decrease sleep‐onset latency. This simple tool has potential for scalable dissemination by stakeholders (e.g. teachers), unqualified to treat adolescent sleep difficulties. Future studies are needed to determine whether benefits may extend to academic performance and mental health, if performed for a longer time period with increased compliance.     

The wrist is not the brain: Estimation of sleep by clinical and consumer wearable actigraphy devices is impacted by multiple patient‐ and device‐specific factors

Clinical actigraphy devices provide adequate estimates of some sleep measures across large groups. In practice, providers are asked to apply clinical or consumer wearable data to individual patient assessments. Inter‐individual variability in device performance will impact such patient‐specific interpretation. We assessed two devices, clinical and consumer, to determine the magnitude and predictors of this individual‐level variability. One hundred and two patients (55 [53.9%] female; 56.4 [±16.3] years old) undergoing polysomnography wore Jawbone UP3 and/or Actiwatch2. Device total sleep time, sleep efficiency, wake after sleep onset and sleep latency were compared with polysomnography. Demographics, sleep architecture and clinical measures were compared to device performance. Actiwatch overestimated total sleep time by 27.2 min (95% confidence limits [CL], 138.3 min over to 84.0 under), overestimated sleep efficiency by 6.8% (95% CL, 34.1% over to 20.5% under), overestimated sleep onset latency by 2.6 min (95% CL, 63.3 over to 58.2 under) and underestimated wake after sleep onset by 50.7 min (95% CL, 162.5 under to 61.2 over). Jawbone overestimated total sleep time by 59.1 min (95% CL, 208.6 min over to 90.5 under) and overestimated sleep efficiency by 14.9% (95% CL, 52.6% over to 22.7% under). In multivariate models, age, sleep onset latency, wake after sleep onset, % N1 and apnea–hypopnea index explained only some of the variance in device performance. Gender also affected performance. Actiwatch and Jawbone mis‐estimate sleep measures with very wide confidence limits and accuracy varies with multiple patient‐level characteristics. Given these large individual inaccuracies, data from these devices must be applied only with extreme caution in clinical practice.     

Assessment of a hearing protection device on infant sleep in the neonatal intensive care unit

Premature infants often require prolonged hospitalisation in the neonatal intensive care unit (NICU) where they are exposed to adverse noise that may disrupt sleep and further compromise recovery and developmental outcomes. This single-session trial assessed the effects of a novel circumaural hearing protection device (DREAMIES®; NEATCAP Medical LLC) on sleep in 10 premature infants (mean 34.1 weeks GA) in a Level III NICU. Using polysomnography (PSG), the infant's sleep was compared between three interfeed periods throughout which DREAMIES® was ON or OFF. Each infant received the same condition order, OFF1-ON-OFF2. The PSG 30 s epochs were scored by a rater masked to the condition as Quiet Sleep, Active Sleep, Indeterminate Sleep, and Wake. There was a 14.1% increase in sleep from OFF1 to ON (p = 0.05) and an 18.4% decrease in sleep from ON to OFF2 (p = 0.02); an analogous inverse effect was observed for wake (χ² = 5.03, p = 0.08). There was a main effect of DREAMIES on active sleep (χ² = 7.4, p = 0.025) due to more active sleep for ON1 (46%) compared with OFF2 (32%; p = 0.074). No significant effect was observed for quiet sleep or indeterminate sleep. On average, the sound level was 51 dBA (range 36–113 dBA) and did not differ significantly among the three periods. The strongest relationship between the minute-by-minute maximum sound level and movement actigraphy was observed for the OFF1 condition (ρ0.301, p < 0.001). These findings suggest that DREAMIES® may augment sleep in premature infants by reducing acute episodes of adverse noise in the NICU.     

Association between objective sleep measures and cognitive performance: a cross-sectional analysis in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) study

Sleep disturbances often co-exist, which challenges our understanding of their potential impact on cognition. We explored the cross-sectional associations of insomnia and objective measures of sleep with cognitive performance in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) study stratified by middle-aged and older adults. Participants aged ≥55 years underwent cognitive evaluations, polygraphy for 1 night, and actigraphy for 7 days. Insomnia was evaluated using the Clinical Interview Scheduled Revised. Obstructive sleep apnea (OSA) and short sleep duration (SSD) were defined by an apnea–hypopnea index (AHI) of ≥15 events/h and <6 h/ night, respectively. In 703 participants (mean [SD] age 62 [6] years, 44% men), cognition was evaluated using a 10-word list, verbal fluency, and trail-making tests. The frequencies of insomnia, SSD, and OSA were 11%, 24%, and 33%, respectively. In all, 4% had comorbid OSA and insomnia, and 11% had both OSA and SSD. Higher wake after sleep onset (β = −0.004, 95% confidence interval [CI] −0.008, −0.001) and the number of awakenings (β = −0.006, 95% CI −0.012, −0.001) were associated with worse verbal fluency performance. Compared to those without insomnia, older participants with insomnia had worse global performance (β = −0.354, 95% CI −0.671, −0.038). Insomnia was an effect modifier in the associations between AHI and executive function performance (p for the interaction between insomnia and AHI = 0.004) and between oxygen saturation <90% and memory performance (p for the interaction between insomnia and oxygen saturation = 0.02). Although some associations between sleep measures and cognition were significant, they should be considered with caution due to the large sample size and multiple testing performed in this study.     

Associations between objective afternoon and evening physical activity and objective sleep in patients with fibromyalgia and insomnia

Patients with fibromyalgia (FM) suffer from chronic pain, which limits physical activity and is associated with disturbed sleep. However, the relationship between physical activity, pain and sleep is unclear in these patients. This study examined whether actigraphic (Actiwatch‐2, Philips Respironics) afternoon and evening activity and pain are associated with actigraphic sleep. Adults with FM and insomnia complaints (n = 160, mean age [M_age] = 52, SD = 12, 94% female) completed 14 days of actigraphy. Activity levels (i.e., activity counts per minute) were recorded, and average afternoon/evening activity for intervals 12:00–3:00 PM, 3:00–6:00 PM and 6:00–9:00 PM was computed. Multiple linear regressions examined whether afternoon/evening activity, pain (daily evening diaries from 0 [no pain sensation] to 100 [most intense pain imaginable]), or their interaction, predicted sleep onset latency (SOL), wake time after sleep onset (WASO), total sleep time (TST) and sleep efficiency (SE). Greater afternoon activity was independently associated with lower SE (B = ?0.08, p < .001), lower TST (β = ?0.36, standard error [SE] = 0.06, p < .001) and longer WASO (B = 0.34, p < .001). Greater early evening activity was independently associated with lower SE (B = ?0.06, p < .001), lower TST (β = ?0.26, SE = 0.06, p < .001) and longer WASO (B = 0.23, p < .001). Self‐reported pain intensity interacted with afternoon and early evening physical activity, such that associations between higher activity and lower SE were stronger for individuals reporting higher pain. Late evening activity was not associated with sleep outcomes. Results suggest that in FM, increased afternoon and early evening physical activity is associated with sleep disturbance, and this relationship is stronger in individuals with higher pain.     

Calibrating actigraphy to improve sleep efficiency estimates

Actigraphy (ACT) can enhance treatment for insomnia by providing objective estimates of sleep efficiency; however, only two studies have assessed the accuracy of actigraphy‐based estimates of sleep efficiency (ACT‐SE) in sleep‐disordered samples studied at home. Both found poor correspondence with polysomnography‐based estimates (PSG‐SE). The current study tested that concordance in a third sample and piloted a method for improving ACT‐SE. Participants in one of four diagnostic categories (panic disorder, post‐traumatic stress disorder, comorbid post‐traumatic stress and panic disorder and controls without sleep complaints) underwent in‐home recording of sleep using concurrent ambulatory PSG and actigraphy. Precisely synchronized PSG and ACT recordings were obtained from 41 participants. Sleep efficiency was scored independently using conventional methods, and ACT‐SE/PSG‐SE concordance examined. Next, ACT data recorded initially at 0.5 Hz were resampled to 30‐s epochs and rescaled on a per‐participant basis to yield optimized concordance between PSG‐ and ACT‐based sleep efficiency estimates. Using standard scoring of ACT, the correlation between ACT‐SE and PSG‐SE across participants was statistically significant (r = 0.35, P < 0.025), although ACT‐SE failed to replicate a main effect of diagnosis. Individualized calibration of ACT against a night of PSG yielded a significantly higher correlation between ACT‐SE and PSG‐SE (r = 0.65, P < 0.001; z = 1.692, P = 0.0452, one‐tailed) and a significant main effect of diagnosis that was highly correspondent with the effect on PSG‐SE. ACT‐based estimates of sleep efficiency in sleep‐disordered patients tested at home can be improved significantly by calibration against a single night of concurrent PSG.     

Age affects sleep microstructure more than sleep macrostructure

It is well known that the quantity and quality of physiological sleep changes across age. However, so far the effect of age on sleep microstructure has been mostly addressed in small samples. The current study examines the effect of age on several measures of sleep macro‐ and microstructure in 211 women (22–71 years old) of the ‘Sleep and Health in Women’ study for whom ambulatory polysomnography was registered. Older age was associated with significantly lower fast spindle (effect size f² = 0.32) and K‐complex density (f² = 0.19) during N2 sleep, as well as slow‐wave activity (log) in N3 sleep (f² = 0.21). Moreover, total sleep time (f² = 0.10), N3 sleep (min) (f² = 0.10), rapid eye movement sleep (min) (f² = 0.11) and sigma (log) (f² = 0.05) and slow‐wave activity (log) during non‐rapid eye movement sleep (f² = 0.09) were reduced, and N1 sleep (f² = 0.03) was increased in older age. No significant effects of age were observed on slow spindle density, rapid eye movement density and beta power (log) during non‐rapid eye movement sleep. In conclusion, effect sizes indicate that traditional sleep stage scoring may underestimate age‐related changes in sleep.     

Toddler's self‐regulation strategies in a challenge context are nap‐dependent

Early childhood represents a time of developmental changes in both sleep and self‐regulation, a construct reflecting the ability to control one's behaviour, attention and emotions when challenged. Links between sleep and self‐regulation processes have been proposed, but experimental evidence with young children is lacking. In the current study, we tested the effects of acute sleep restriction (nap deprivation) on toddlers’ self‐regulation. Healthy children (n = 12; four males; aged 30–36 months (33.9 ± 1.7)) slept on a strict schedule (verified with actigraphy and sleep diaries) for 5 days before each of two afternoon assessments following a nap and a no‐nap condition (~11‐day protocol). Children were videotaped while attempting an unsolvable puzzle, and 10 mutually exclusive self‐regulation strategies were later coded. On average, children lost ~90 min of sleep on the no‐nap versus the nap day. Nap deprivation resulted in moderate‐to‐large effects on self‐regulation strategies, with decreases in scepticism (d = 0.77; 7% change), negative self‐appraisal (d = 0.92; 5% change) and increases in physical self‐soothing (d = 0.68; 10% change), focus on the puzzle piece that would not fit (perseveration; d = 0.50; 9% change) and insistence on completing the unsolvable puzzle (d = 0.91; 10% change). Results suggest that sleep serves an important role in the way that toddlers respond to challenging events in their daily lives. After losing daytime sleep, toddlers were less able to engage effectively in a difficult task and reverted to less mature self‐regulation strategies than when they were well rested. Over time, chronically missed sleep may impair young children's self‐regulation abilities, resulting in risk for social–emotional, behavioural and school problems.     

Ambulatory detection of sleep apnea using a non‐contact biomotion sensor

The high prevalence of obstructive sleep apnea has led to increasing interest in ambulatory diagnosis. The SleepMinder? (SM) is a novel non‐contact device that employs radiofrequency wave technology to assess the breathing pattern, and thereby estimate obstructive sleep apnea severity. We assessed the performance of SleepMinder? in the home diagnosis of obstructive sleep apnea. One‐hundred and twenty‐two subjects were prospectively recruited in two protocols, one from an unselected sleep clinic cohort (n = 67, mean age 51 years) and a second from a hypertension clinic cohort (n = 55, mean age 58 years). All underwent 7 consecutive nights of home monitoring (SM_HOME) with the SleepMinder? as well as inpatient‐attended polysomnography in the sleep clinic cohort or cardiorespiratory polygraphy in the hypertension clinic cohort with simultaneous SleepMinder? recordings (SM_LAB). In the sleep clinic cohort, median SM_HOME apnea–hypopnea index correlated significantly with polysomnography apnea–hypopnea index (r = .68; p < .001), and in the hypertension clinic cohort with polygraphy apnea–hypopnea index (r = .7; p < .001). The median SM_HOME performance against polysomnography in the sleep clinic cohort showed a sensitivity and specificity of 72% and 94% for apnea–hypopnea index ≥ 15. Device performance was inferior in females. In the hypertension clinic cohort, SM_HOME showed a 50% sensitivity and 72% specificity for apnea–hypopnea index ≥ 15. SleepMinder? classified 92% of cases correctly or within one severity class of the polygraphy classification. Night‐to‐night variability in home testing was relatively high, especially at lower apnea–hypopnea index levels. We conclude that the SleepMinder? device provides a useful ambulatory screening tool, especially in a population suspected of obstructive sleep apnea, and is most accurate in moderate–severe obstructive sleep apnea.     

Obstructive sleep apnea and hypertriglyceridaemia share common genetic background: Results of a twin study

Obstructive sleep apnea is associated with an increased risk of hypertension, diabetes and dyslipidaemia. Both obstructive sleep apnea and its comorbidities are at least partly heritable, suggesting a common genetic background. Our aim was to analyse the heritability of the relationship between obstructive sleep apnea and its comorbidities using a twin study. Forty‐seven monozygotic and 22 dizygotic adult twin pairs recruited from the Hungarian Twin Registry (mean age 51 ± 15 years) attended an overnight diagnostic sleep study. A medical history was taken, blood pressure was measured, and blood samples were taken for fasting glucose, total cholesterol, triglyceride, high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol and lipoprotein (a). To evaluate the heritability of obstructive sleep apnea and its comorbidities bivariate analysis was performed with an adjustment for age, gender, body mass index (BMI) and smoking after false discovery rate correction and following exclusion of patients on lipid‐lowering and antidiabetic medications. There was a significant correlation between indices of obstructive sleep apnea severity, such as the apnea–hypopnea index, oxygen desaturation index and percentage of sleep time spent with oxygen saturation below 90%, as well as blood pressure, serum triglyceride, lipoprotein (a) and glucose levels (all p < .05). The bivariate analysis revealed a common genetic background for the correlations between serum triglyceride and the oxygen desaturation index (r = .63, p = .03), as well as percentage of sleep time spent with oxygen saturation below 90% (r = .58, p = .03). None of the other correlations were significantly genetically or environmentally determined. This twin study demonstrates that the co‐occurrence of obstructive sleep apnea with hypertriglyceridaemia has a genetic influence and heritable factors play an important role in the pathogenesis of dyslipidaemia in obstructive sleep apnea.     

Validity,potential clinical utility and comparison of a consumer activity tracker and a research‐grade activity tracker in insomnia disorder II: Outside the laboratory

Accurate assessment of sleep can be fundamental for monitoring, managing and evaluating treatment outcomes within diseases. A proliferation of consumer activity trackers gives easy access to objective sleep. We evaluated the performance of a commercial device (Fitbit Alta HR) relative to a research‐grade actigraph (Actiwatch Spectrum Pro) in measuring sleep before and after a cognitive behavioural intervention in insomnia disorder. Twenty‐five individuals with DSM‐5 insomnia disorder (M = 50.6 ± 15.9 years) wore Fitbit and Actiwatch and completed a sleep diary during an in‐laboratory polysomnogram, and for 1 week preceding and following seven weekly sessions of cognitive‐behavioural intervention for insomnia. Device performance was compared for sleep outcomes (total sleep time, sleep latency, sleep efficiency and wake after sleep onset). The analyses assessed (a) agreement between devices across days and pre‐ to post‐treatment, and (b) whether pre‐ to post‐treatment changes in sleep assessed by devices correlated with clinical measures of change. Devices generally did not significantly differ from each other on sleep variable estimates, either night to night, in response to sleep manipulation (pre‐ to post‐treatment) or in response to changes in environment (in the laboratory versus at home). Change in sleep measures across time from each device showed some correlation with common clinical measures of change in insomnia, but not insomnia diagnosis as a categorical variable. Overall, the Fitbit provides similar estimates of sleep outside the laboratory to a research grade actigraph. Despite the similarity between Fitbit and Actiwatch performance, the use of consumer technology is still in its infancy and caution should be taken in its interpretation.     

Wrist actigraphic scoring for sleep laboratory patients: algorithm development

Wrist actigraphy is employed increasingly in sleep research and clinical sleep medicine. Critical evaluation of the performance of new actigraphs and software is needed. Actigraphic sleep–wake estimation was compared with polysomnographic (PSG) scoring as the standard in a clinical sleep laboratory. A convenience sample of 116 patients undergoing clinical sleep recordings volunteered to participate. Actiwatch‐L recordings were obtained from 98 participants, along with 18 recordings using the newer Spectrum model (Philips Electronics), but some of the actigraphic recordings could not be adequately aligned with the simultaneous PSGs. Of satisfactory alignments, 40 Actiwatch recordings were used as a training set to empirically develop a new Scripps Clinic algorithm for sleep–wake scoring. The Scripps Clinic algorithm was then prospectively evaluated in 39 Actiwatch recordings and 16 Spectrum recordings, producing epoch‐by‐epoch sleep–wake agreements of 85–87% and kappa statistics averaging 0.52 (indicating moderate agreement). Wake was underestimated by the scoring algorithm. The correlations of PSG versus actigraphic wake percentage estimates were r = 0.6690 for the Actiwatch and r = 0.2197 for the Spectrum. In general, using a different weighting of activity counts from previous and subsequent epochs, the Scripps Clinic algorithm discriminated sleep–wake more successfully than the manufacturer’s Actiware algorithms. Neither algorithm had fully satisfactory agreement with PSG. Further evaluations of algorithms for these actigraphs are needed, along with controlled comparisons of different actigraphic designs and software.     

Sleep condition and cognitive decline in Japanese community‐dwelling older people: Data from a 4‐year longitudinal study

This study examined whether sleep duration and excessive daytime sleepiness (EDS) are related to cognitive decline among community‐dwelling older adults with intact cognition at baseline, using 4‐year longitudinal data. A total of 3,151 community‐dwelling older individuals aged ≥65 years were studied. They were assessed for cognitive function, including memory, attention, executive function and processing speed. Cognitive impairment was defined based on a score >1.5 standard deviations below the age‐ and education‐specific mean. Cognitive decline was defined in one or more cognitive tests at follow‐up. Self‐reported sleep duration (short, ≤6.0 hr; medium, 6.1–8.9 hr; long, ≥9.0 hr) and EDS at first‐wave examination were assessed and logistic regression analyses were used to examine the associations of sleep duration and EDS with cognitive status at second‐wave examination. The incidence of cognitive decline differed significantly among the sleep‐duration groups (short, 15.9%; medium, 11.9%; long, 20.1%; p = 0.001). The prevalence of having EDS was 13.1%, which was associated with a higher rate of cognitive decline than having no EDS (18.9% vs. 12.5%, p = 0.004). Long sleep duration compared with medium sleep duration (OR, 1.50; 95% CI, 1.05–2.13) and EDS (1.43; 1.01–2.03) independently impacted the incidence of cognitive decline. The results were similar after multiple imputations (long, 1.68, 1.12–2.52; EDS, 1.55, 1.05–2.29). In conclusion, our study revealed that both long sleep duration and EDS were independent risk factors associated with cognitive decline after 4 years among older adults.     

Short persistent sleep duration is associated with poor receptive vocabulary performance in middle childhood

The aim of this study was to examine whether short sleep duration is associated with poor receptive vocabulary at age 10 years. In the Quebec Longitudinal Study of Child Development, parents reported their children's nocturnal sleep duration annually from ages 2.5 to 10 years, and children were assessed for receptive vocabulary using the Peabody Picture Vocabulary Test—Revised (PPVT‐R) at ages 4 and 10 years. Groups with distinct nocturnal sleep duration trajectories were identified and the relationships between sleep trajectories and poor PPVT‐R performance were characterized. In all, 1192 children with available sleep duration and PPVT‐R data participated in this epidemiological study. We identified four longitudinal nocturnal sleep trajectories: short persistent sleepers (n = 72, 6.0%), short increasing sleepers (n = 47, 3.9%), 10‐h sleepers (n = 628, 52.7%) and 11‐h sleepers (n = 445, 37.3%). In all, 14.8% of the children showed poor PPVT‐R performance at age 10 years. Nocturnal sleep trajectories and poor PPVT‐R performance at age 10 were associated significantly (P = 0.003). After adjusting for baseline receptive vocabulary performance at age 4 and other potential confounding variables, logistic regression analyses suggest that, compared to 11‐h sleepers, the odds ratio of presenting poor receptive vocabulary at age 10 was 2.67 [95% confidence interval (CI): 1.24–5.74, P = 0.012] for short persistent sleepers and 1.66 (95% CI: 1.06–2.59, P = 0.026) for 10‐h sleepers. These results corroborate previous findings in early childhood, and indicate that short sleep duration is associated with poor receptive vocabulary during middle childhood.     

Genetic risk factors for schizophrenia associate with sleep spindle activity in healthy adolescents

Schizophrenia has been associated with disturbed sleep, even before the onset of the disorder, and also in non‐schizophrenic first‐order relatives. This may point to an underlying genetic influence. Here we examine whether weighted polygenic risk scores (PRS) for schizophrenia are associated with sleep spindle activity in healthy adolescents. Our sample comes from a community‐based cohort of 157 non‐schizophrenic adolescents (57% girls) having both genetic data and an overnight sleep EEG measurement available. Based on a recent genome‐wide association study, we calculated PRS for schizophrenia across the whole genome. We also calculated PRS for the CACNA1l gene region, which has been associated with both schizophrenia and sleep spindle formation. We performed an overnight sleep EEG at the homes of the participants. Stage two sleep spindles were detected using an automated algorithm. Sleep spindle amplitude, duration, intensity and density were measured separately for central and frontal derivations and for fast (13–16 Hz) and slow (10–13 Hz) spindles. PRS for schizophrenia was associated with higher fast spindle amplitude (p = 0.04), density (p = 0.006) and intensity (p = 0.04) at the central derivation, and PRS in the CACNA1l region associated with higher slow spindle amplitude (p = 0.01), duration (p = 0.03) and intensity (p = 0.002) at the central derivation. A positive association between genetic variants for schizophrenia and sleep spindle activity among healthy adolescents supports a view that sleep spindles and schizophrenia share similar genetic pathways. This study suggests that altered sleep spindle activity might serve as an endophenotype of schizophrenia.