Newly developed waist actigraphy and its sleep/wake scoring algorithm

Association between Social Jetlag and Objective Physical Activity among Female University Students of Japan: A Cross-Sectional Study

Objective  Discrepancies between sleep timing on work/school and free days, also known as social jetlag (SJL), can cause health problems. These issues occur most often in individuals from adolescence to the early 20s, which is equivalent to the age of university students. This study was designed to explore the recommended level of physical activity required to minimize SJL and to examine the relationship between SJL and objective physical activity among female university students. Methods  We assessed the SJL of 68 female students using the Japanese version of the Munich Chronotype Questionnaire. The objective physical activity and sleep variables of subjects were also evaluated at 3 to 4 weeks using a small triaxial accelerometer. Results  A significant negative correlation was found between SJL and physical activity on both free (r = - 0.435, p  < 0.001) and school days (r = - 0.341, p  < 0.01). According to the linear regression analysis, physical activity of 11,174 steps on school days and 10,713 steps on free days had the lowest SJL value. Total sleep time on free days had a significant positive correlation with SJL (r = 0.399, p  < 0.001) and a negative correlation with physical activity (r = - 0.520, p  < 0.001). Discussion  Our results suggest that substantial SJL may cause chronic fatigue and lead to a low level of physical activity in female university students. These results also imply that the recommended level of physical activity necessary to minimize SJL among these students is around 11,000 steps on both school and free days.

Evaluation of the benefits of neutral bicarbonate ionized water baths in an open-label, randomized, crossover trial

We previously demonstrated that neutral bicarbonate ionized water (NBIW) bathing enhances blood flow by bicarbonate ions and described the underlying mechanism. However, additional clinical investigation was warranted to investigate the efficacy of NBIW bathing. Hence, we performed a randomized, open-label, crossover trial to examine the effects of NBIW bathing on mental stress, sleep, and immune function. Participants who regularly felt stressed were randomly assigned to NBIW or regular bathing for 4 weeks. Mental stress was assessed with the Brief Job Stress Questionnaire (BJSQ) and the Profile of Mood States Second Edition; sleep quality, with the Pittsburgh Sleep Quality Index Japanese version (PSQI-J) and actigraphy; and immune function, with laboratory tests. PSQI-J scores and actigraphy sleep latency and bed out latency improved significantly more with NBIW bathing than with regular bathing (p < 0.05). Furthermore, NBIW bathing reduced both stress-induced fluctuations in CD4+ and CD8+ T cell counts and fluctuations in the naive to memory T cell ratio and neutrophil phagocytosis, indicating improved immune function. These findings suggest that daily NBIW bathing could improve mental stress, sleep quality, and immune function and bring about positive health effects in those who experience stress in their daily lives.

Potential Benefits of Daytime Naps on Consecutive Days for Motor Adaptation Learning

Daytime napping offers benefits for motor memory learning and is used as a habitual countermeasure to improve daytime functioning. A single nap has been shown to ameliorate motor memory learning, although the effect of consecutive napping on motor memory consolidation remains unclear. This study aimed to explore the effect of daytime napping over multiple days on motor memory learning. Twenty university students were divided into a napping group and no-nap (awake) group. The napping group performed motor adaption tasks before and after napping for three consecutive days, whereas the no-nap group performed the task on a similar time schedule as the napping group. A subsequent retest was conducted one week after the end of the intervention. Significant differences were observed only for speed at 30 degrees to complete the retention task, which was significantly faster in the napping group than in the awake group. No significant consolidation effects over the three consecutive nap intervention periods were confirmed. Due to the limitations of the different experimental environments of the napping and the control group, the current results warrant further investigation to assess whether consecutive napping may benefit motor memory learning, which is specific to speed.

Validity of an algorithm for determining sleep/wake states using FS-760 in school-aged children

Background

Actigraphy is a method used for determining sleep (S)/wakefulness (W) by actigraph, a device equipped with a built-in accelerometer and an algorithm validated for each device. The S/W determination algorithm for the waist-worn actigraph FS-760 has been formulated for adults. However, the algorithm for children has not been established. The purpose of this study was to formulate an algorithm for discriminating S/W in school-aged children using FS-760 and to evaluate its validity. We further tested the generalizability of existing algorithm for adults by applying it to the children’s activity data and then examined factors associated with adult algorithm agreement rates by multiple regression analysis using combined adult and children data.

Methods

Sixty-five, healthy, school-aged children (aged 6 to 15 years) were recruited and randomly assigned to two groups: A (n = 33) and B (n = 32). They underwent 8-h polysomnography (PSG) and wore FS-760 simultaneously to obtain activity data. To determine the central epoch of the sleep/wake states (𝑥), a five-order linear discriminant analysis was conducted using the activity intensity of group A for five epochs (𝑥₋₂, 𝑥₋₁, 𝑥, 𝑥₊₁, 𝑥₊₂; 10 min) and evaluate its accuracy with the activity of group B. To reveal the factors associated with adult algorithm agreement rate, we integrated the activity, age, sleep efficiency of 15 adults (aged 20 to 39 years) and those of 65 children for multiple regression analysis.

Results

The mean agreement rate of the developed algorithm was 91.0%, with a mean sensitivity (true sleep detection rate) of 93.0% and a mean specificity (true wakefulness detection rate) of 63.9%. The agreement rate of the adult algorithm applied to children’s activity was significantly lower (81.8%) than that of the children algorithm. Multiple regression analysis showed that the agreement rates calculated by the adult algorithm were significantly related to mean activity of the 𝑥 epoch in NREM and REM sleep as well as age and sleep efficiency.

Conclusions

The S/W states in school-aged children can be reliably assessed using the developed algorithm for waist-worn actigraph FS-760. Since the accuracy of the adult algorithms decreased when applied it to children which have different activity levels during sleep, the establishment and validation of population-specific S/W algorithms should be required.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-022-00303-2.

Effect of napping on a bean bag chair on sleep stage, muscle activity, and heart rate variability

Background

Although ample evidence has demonstrated that daytime napping is beneficial for health and cognitive performance, bedding for napping has not yet been scientifically investigated.

Objectives

To explore the effect of a bean bag chair on daytime napping and physiological parameters related to sleep.

Methods

Fourteen healthy participants were enrolled within the context of a randomized, single-blind, crossover study to evaluate the effects of a bean bag chair in comparison with those of a urethane chair manufactured to have a similar shape. Electroencephalogram, electromyogram, and heart rate variability were recorded and compared between wakefulness and napping.

Results

Electroencephalogram analyses revealed no significant differences in sleep architecture or frequency components; however, a significant decrease was found in electromyogram recordings in the trapezius muscle, which represents the neck region (p = 0.019). Additionally, a significant main effect of bedding in the low-frequency/high-frequency ratio (F[1,20] = 4.314, p = 0.037) was revealed.

Conclusions

These results suggest that napping in a bean bag chair may provide a comfortable napping environment involving muscle relaxation and proper regulation of the autonomic nervous function.

Morning preference is associated with subjective happiness among Japanese female workers: A moderation analysis by sleep characteristics from the SLEPT study

Research on mental health in working populations has predominantly focussed on negative outcomes, while studies on the positive aspects of life remain very limited, especially in Japan. Although morningness has recently been considered a factor for being happy, the role of sleep characteristics as it relates to the association between morningness and happiness has not been substantiated. The aim of this study is to investigate the associations between diurnal preference and level of subjective happiness in healthy, full-time, daytime workers in Japan. We also tested the moderation effect of sleep parameters on the relationship between diurnal preference and subjective happiness. This is an exploratory analysis from the cross-sectional data of the SLeep Epidemiology Project at the University of Tsukuba (SLEPT Study). Subjective happiness was evaluated using a single-item question. Diurnal preference was assessed using the Morningness-Eveningness Questionnaire (MEQ), in which higher scores indicate greater tendency to have morning preference. The participants underwent assessment of sleep parameters for 7 consecutive days using a waist-worn actigraphy device and kept a sleep diary. Sleep parameters investigated were subjective sleep quality, sleep disturbance, daytime sleepiness, weekend oversleep, total sleep time, sleep onset time, wake time, and sleep efficiency. A total of 205 males (average 42.6 ± 10.4 years) and 272 females (41.1 ± 9.8 years) were eligible for analysis. Hierarchical liner regression analysis was used to show the relationships of subjective happiness with MEQ score, and the sleep parameters. Further, moderation analysis was conducted by adding the interaction between MEQ score and the sleep parameters. After adjusting for age, psychological distress, self-rated health, and occupational stress, we found that subjective happiness was significantly associated with higher MEQ score and sleep efficiency but only in female. The moderating role of sleep parameters was not found. We discussed the implications of the obtained results and a possible strategy to maintain and improve subjective happiness of female workers who have evening preference.

Effects of light-to-moderate intensity aerobic exercise on objectively measured sleep parameters among community-dwelling older people

OBJECTIVES

Although exercise improves sleep parameters in older people, most studies have been designed for people with insomnia or sleep complaints. Little is known of the effects of exercise among older people without sleep problems. We investigated the effects of 3-month light-to-moderate intensity aerobic exercise intervention on objectively measured sleep quantity and quality among community-dwelling older people.

METHODS

Fifty-eight community-dwelling older people were assigned into an exercise (EX) or control (CON) groups, and 49 participants (65.7 ± 5.7 years. BMI 24.4 ± 3.9 kg/m²) were enrolled in the analysis. EX group members attended 60 min/week group-based exercise program and performed ≥140 min of home-based exercise, at ≥50% of maximum heart rate to exceed 200 min of total exercise per week. Sleep was assessed by an accelerometer and the Pittsburgh Sleep Quality Index (PSQI) before and after intervention.

RESULTS

In the EX group, total sleep time, hours in waking after sleep onset, sleep efficiency and consecutive wake episodes ≥10 min (WE≥10 min) significantly improved (p<0.05). EX group showed a significantly greater reduction in WE≥10 min than the CON group (p<0.05). The subgroup analyses in the EX group according to baseline PSQI cutoff value showed no differences in changes between subgroups.

CONCLUSIONS

Three-month aerobic exercise improved objectively measured sleep quality in community-dwelling older people. Baseline sleep conditions did not significantly influence the magnitude of changes in sleep quality and quantity. These results suggest that light aerobic exercise can improve sleep among community-dwelling older people, regardless of baseline sleep status, but the effect may be small.

Relationship between physical activity and circulating fibroblast growth factor 21 in middle-aged and older adults

OBJECTIVE

Circulating levels of fibroblast growth factor 21 (FGF21) increase with advancing age and may lead to the development of cardiometabolic diseases via impaired lipid and glucose metabolism. While physical activity can reduce these risks of cardiometabolic dysfunction, it remains obscure whether circulation FGF21 levels are influenced by physical activity. The purpose of this study was to investigate the relations between daily physical activities and circulating FGF21 levels in middle-aged and older adults.

METHODS

In this cross-sectional study with 110 middle-aged and 102 older adults, circulating (serum) FGF21 levels were evaluated by enzyme-linked immunosorbent assay, and the time spent in light-intensity physical activity (LPA) and moderate-to-vigorous-intensity physical activity (MVPA) was assessed using a uniaxial accelerometer.

RESULTS

Serum FGF21 levels in the older group (158 pg/mL) were significantly higher than those in the middle-aged group (117 pg/mL). When we examined the joint association of age (middle-aged or older) and MVPA (lower or higher than the median) groups, serum FGF21 levels in the older and higher MVPA group (116 pg/mL) were significantly lower than those in the older and lower MVPA group (176 pg/mL). However, there was no difference in serum FGF21 levels between the lower and higher MVPA groups in the middle-aged group. In multivariable liner regression analysis, serum FGF21 levels were independently determined by MVPA time after adjusting for potential covariates in older adults (β = -0.209).

CONCLUSIONS

These cross-sectional study findings indicate that the time spent in MVPA is an independent determinant of circulating FGF21 levels, and that an age-related increase in serum FGF21 levels may be attenuated by habitually performing MVPA. (250/250 words).

ActiGraph GT3X+ and Actical Wrist and Hip Worn Accelerometers for Sleep and Wake Indices in Young Children Using an Automated Algorithm: Validation With Polysomnography

Objectives: Our count-scaled algorithm automatically scores sleep across 24 hours to process sleep timing, quantity, and quality. The aim of this study was to validate the algorithm against overnight PSG in children to determine the best site placement for sleep. Methods: 28 children (5-8 years) with no history of sleep disturbance wore two types of accelerometers (ActiGraph GT3X+ and Actical) at two sites (left hip, non-dominant wrist) for 24-h. Data were processed using the count-scaled algorithm. PSG data were collected using an in-home Type 2 device. PSG-actigraphy epoch sensitivity (sleep agreement) and specificity (wake agreement) were determined and sleep outcomes compared for timing (onset and offset), quantity [sleep period time (SPT) and total sleep time (TST)], and quality metrics [sleep efficiency and waking after sleep onset (WASO)]. Results: Overall, sensitivities were high (89.1% to 99.5%) and specificities low (21.1% to 45.7%). Sleep offset was accurately measured by actigraphy, regardless of brand or placement site. By contrast, sleep onset agreed with PSG using hip-positioned but not wrist-positioned devices (difference ActiGraph : PSG 21 min, P < .001; Actical : PSG 14 min, P < .001). The ActiGraph at the wrist accurately detected WASO and sleep efficiency, but under (-34 min, P < .001) and overestimated (5.8%, P < .001) these at the hip. The Actical under- and over-estimated these variables respectively at both sites. Results for TST varied ranging from significant differences to PSG of -26 to 21 min (ActiGraph wrist and hip respectively) and 9 min (ns) to 59 min for Actical (wrist and hip respectively). Conclusion: Overall the count-scaled algorithm produced high sensitivity at the expense of low specificity in comparison with PSG. A best site placement for estimates of all sleep variables could not be determined, but overall the results suggested ActiGraph GT3X+ at the hip may be superior for sleep timing and quantity metrics, whereas the wrist may be superior for sleep quality metrics. Both devices placed at the hip performed well for sleep timing but not for sleep quality. Differences are likely linked to freedom of movement of the wrist vs the trunk (hip) during overnight sleep.

Objectively measured habitual physical activity and sleep-related phenomena in 1645 people aged 1-91 years: The Nakanojo Community Study

Relationships between habitual physical activity and sleep-related phenomena were examined in 623 male and 1022 female Japanese participating in the Nakanojo Community Study, using data collected in 2012–2013. Ages ranged from infancy to very old. Daily step count and daily duration of exercise at an intensity >3 metabolic equivalents (METs) were determined by pedometer/accelerometer, 24 h/day for 1 week. Duplicate axillary temperatures were also taken on rising and when retiring. Total bed time was noted, and the efficiency of sleep determined as hours of actual sleep (from a validated pedometer/accelerometer algorithm) divided by bed time. Step counts and especially duration of activity >3 METs peaked in teenagers and decreased as age advanced (p < 0.001). Both axillary temperatures subsequently showed a gradual age-related decline (p < 0.001). The duration and efficiency of sleep also showed a small age-dependent decrease (p < 0.001). Multivariate-adjusted correlation coefficients indicated a better quality of sleep in individuals who took greater habitual physical activity. In individuals aged ≥40 years, these findings were modified by chronic disease conditions including hypertension, diabetes mellitus and hyperlipemia; after controlling statistically for potential confounders, both physical activity and axillary temperature were lower (p < 0.05 or 0.01), and the time spent lying was longer but the efficiency of sleep was poorer (p < 0.01) in those with chronic conditions. These results suggest that habitual physical activity bears an important relationship to sleep-related phenomena at all ages, with a modification of relationships by chronic disease in people aged ≥40 years.

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Habitual physical activity is related to body temperature and sleep patterns.

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Body temperature is higher and sleep quality is better in physically active people.

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In people aged ≥40 years, these relationships are modified by chronic disease.

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Physical activity and body temperature are lower in older people with chronic disease.

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The time spent lying is longer but the quality of sleep is poorer in such people.

Actigraphy in Patients With Major Depressive Disorder Undergoing Repetitive Transcranial Magnetic Stimulation: An Open Label Pilot Study

BACKGROUND

The effects of repetitive transcranial magnetic stimulation (rTMS) on physical activity and sleep patterns in individuals with major depressive disorder (MDD) remain unclear.

METHOD

We examined the effects of rTMS treatment on the rest-activity cycle and sleep disturbances in MDD. In this open-label pilot study, 14 patients with medication-resistant MDD underwent 10 rTMS sessions over the bilateral dorsolateral prefrontal cortex. In addition to Hamilton Depression Rating Scale and Pittsburgh Sleep Quality Index scores, waist actigraphy was used to evaluate alterations in the rest-activity cycle over the course of rTMS treatments. Actigraphic data were evaluated at baseline and in the first (rTMS sessions 1-3), second (rTMS sessions 4-7), and third (rTMS sessions 8-10) sections.

RESULTS

Although Hamilton Depression Rating Scale and Pittsburgh Sleep Quality Index scores were significantly improved by rTMS, sleep variables assessed by actigraphy did not show significant changes. However, post hoc tests indicated a significant increase in mean steps per day between the baseline and first section time points (P = 0.014; t13 = -2.316).

CONCLUSIONS

Our data indicated that a daytime physical activity response to rTMS occurred in early sessions, whereas subjective symptom improvements were consistent across all sessions. Future double-blind placebo-controlled studies assessing the effects of rTMS on the rest-activity cycle and sleep disturbances in MDD are warranted.

Sleep complaints are associated with reduced left prefrontal activation during a verbal fluency task in patients with major depression: A multi-channel near-infrared spectroscopy study

BACKGROUND

Recent studies have indicated the potential clinical use of near-infrared spectroscopy (NIRS) as a tool for assisting in the diagnosis of major depressive disorder (MDD). Although sleep complaints are often manifested in MDD, no study has elucidated the possible association between the objective evaluation of sleep and NIRS signals in MDD.

METHODS

Fourteen patients with MDD and 15 healthy controls wore waist actigraphy equipment before the NIRS scan to investigate sleep parameters. We performed a 52-channel NIRS scan and measured changes in oxygenated hemoglobin ([oxy-Hb]) during a verbal fluency task.

RESULTS

In patients with MDD, a significant negative correlation was observed between the 17-item Hamilton Depressive Rating Scale score and cerebral reactivity of the right temporal region (p_s:=-0.804 to -0.762; FDR-corrected; p=0.008-0.012). The Pittsburgh Sleep Questionnaire Index, which enables assessment of continuous sleep quality and disturbances, was negatively correlated with [oxy-Hb] changes in the left prefrontal cortex (p_s=-0.630 to -0.551; FDR-corrected; p=0.043-0.048). Actigraphic sleep variables prior to the NIRS measurement showed no significant correlation with [oxy-Hb] changes.

LIMITATIONS

The limitations were small sample size with the low severity of depression and the use of actigraphy for only one night.

CONCLUSION

Self-rated sleep disturbance were associated with decreased left prefrontal reactivity during a verbal fluency task in patients with MDD. Our result indicates that the reactivity of the prefrontal region is susceptible to sleep complaints, providing further evidence to support potential clinical application of NIRS.

Night duty and decreased brain activity of medical residents: a wearable optical topography study

BACKGROUND

Overwork, fatigue, and sleep deprivation due to night duty are likely to be detrimental to the performance of medical residents and can consequently affect patient safety.

OBJECTIVE

The aim of this study was to determine the possibility of deterioration of cerebral function of sleep-deprived, fatigued residents using neuroimaging techniques.

DESIGN

Six medical residents were instructed to draw blood from artificial vessels installed on the arm of a normal cooperator. Blood was drawn at a similar time of the day, before and after night duty. To assess sleep conditions during night duty, the participants wore actigraphy units throughout the period of night duty. Changes in cerebral hemodynamics, during the course of drawing blood, were measured using a wearable optical topography system.

RESULTS

The visual analogue scale scores after night duty correlated negatively with sleep efficiency during the night duty (ρ = -0.812, p = 0.050). The right prefrontal cortex activity was significantly decreased in the second trial after night duty compared with the first (p = 0.028). The extent of [oxy-Hb] decrease, indicating decreased activity, in the right dorsolateral prefrontal cortex correlated negatively with the Epworth sleepiness score after night duty (ρ = -0.841, p = 0.036).

CONCLUSIONS

Sleep deprivation and fatigue after night duty, caused a decrease in the activity of the right dorsolateral prefrontal cortex of the residents, even with a relatively easy routine. This result implies that the brain activity of medical residents exposed to stress on night duty, although not substantially sleep-deprived, was impaired after the night duty, even though they apparently performed a simple medical technique appropriately. Reconsideration of the shift assignments of medical residents is strongly advised.

ABBREVIATIONS

DLPFC: Dorsolateral prefrontal cortex; ESS: Epworth sleepiness scale; PSQI: Pittsburgh sleep quality index; ROI: Regions of interest; VAS: Visual analogue scale; WOT: Wearable optical topography.

Sleep Assessment in Large Cohort Studies with High-Resolution Accelerometers

Accelerometry can be a practical replacement for polysomnography in large observational studies. This review discusses the need for sleep characterization in large observational studies, exemplified by the practices of the ongoing German National Cohort study. After brief descriptions of the physical principles and state-of-the-art accelerometer devices and an overview of public data analysis algorithms for sleep-wake differentiation, we demonstrate that the spectral properties of acceleration data provide additional features that can be exploited. This leads to a periodogram-based sleep detection algorithm. Finally, we address issues of data handling and quality assurance in large cohort studies.

Jogging Therapy for Hikikomori Social Withdrawal and Increased Cerebral Hemodynamics: A Case Report

Severe social withdrawal, called hikikomori, has drawn increased public attention. However, an optimal clinical approach and strategy of treatment has not been well established. Here, we report a case of hikikomori for which an exercise intervention using jogging therapy was effective, showing cerebral hemodynamic improvement. The patient was a 20 year old Japanese male who was hospitalized in order to evaluate and treat severe social withdrawal. Although depressive and anxiety symptoms partially subsided with sertraline alone, social withdrawal persisted due to a lack of self confidence. With his consent, we implemented exercise therapy with 30 minutes of jogging three times a week for three months. We did not change the pharmacotherapy, and his social withdrawal remarkably improved with continuous jogging exercise. Using near infrared spectroscopy to evaluate hemodynamic alteration, bilateral temporal hemodynamics considerably increased after the three-month jogging therapy. Regarding exercise therapy for mental illness, numerous studies have reported the effectiveness of exercise therapy for major depression. This case implied, however, that the applicability of exercise therapy is not limited to major depressive disorder. Jogging therapy may contribute to reinforcing self confidence associated with “resilience” in conjunction with neurophysiological modulation of neural networks.

Criteria for nap identification in infants and young children using 24-h actigraphy and agreement with parental diary

STUDY OBJECTIVES

The study aimed to determine if an automated algorithm, capable of batch scoring, could extract naps and other 24-h sleep-wake variables from actigraphy without the need for parental sleep diaries, which rely heavily on parental awareness of child sleep.

DESIGN

A cross-sectional design was used for the study.

SETTING

The study examined healthy infants/children in their home setting.

PARTICIPANTS

A total of 160 infants/children in five age groups (6 months, and 1, 2, 3½ and 5 years) participated in the study.

MEASUREMENTS AND RESULTS

Participants wore actigraphs for 5-7 days, and parents completed sleep diaries over 2 consecutive days. Three criteria were applied to find the minimum sleep time (20, 30 and 40 min) yielding the best nap agreement between diaries and actigraphy for nap/no-nap identification. Best agreements were 72.1% (20 min minimum), 78.4% (20 min), 91.0% (30 min) and 93.3% (30 min) for ages 6 months, 1, 2 and 3½ years, respectively. Kappa statistics classified nap-nap agreement as 'slight' for 6-month data but 'moderate' or 'almost perfect' for older age groups. The number of daytime naps extracted at each age group yielded no significant discrepancies between the methods. Diaries generally returned significantly earlier sleep onset, later sleep offset, longer sleep duration and fewer night wakings at 6 months and 1 and 2 years, but this was not significant at 3½ or 5 years of age.

CONCLUSIONS

Minimum age-specific sleep time thresholds are recommended to improve nap identification in actigraphy across infant and toddler age groups. The findings strengthen our confidence in the ability to collect actigraphy data in the absence of parental diaries, in 3½- and 5-year-olds, at least.

Validity of an algorithm for determining sleep/wake states using a new actigraph

BACKGROUND

This study aimed to develop an algorithm for determining sleep/wake states by using chronological data on the amount of physical activity (activity intensity) measured with the FS-750 actigraph, a device that can be worn at the waist, allows for its data to be downloaded at home, and is suitable for use in both sleep research and remote sleep medicine.

METHODS

Participants were 34 healthy young adults randomly assigned to two groups, A (n =17) and B (n =17), who underwent an 8-hour polysomnography (PSG) in the laboratory environment. Simultaneous activity data were obtained using the FS-750 attached at the front waist. Sleep/wake state and activity intensity were calculated every 2 minutes (1 epoch). To determine the central epoch of the sleep/wake states (x), a five-variable linear model was developed using the activity intensity of Group A for five epochs (x-2, x-1, x, x+1, x+2; 10 minutes). The optimal coefficients were calculated using discriminant analysis. The agreement rate of the developed algorithm was then retested with Group B, and its validity was examined.

RESULTS

The overall agreement rates for group A and group B calculated using the sleep/wake score algorithm developed were 84.7% and 85.4%, respectively. Mean sensitivity (agreement rate for sleep state) was 88.3% and 90.0% and mean specificity (agreement rate for wakeful state) was 66.0% and 64.9%, respectively. These results confirmed comparable agreement rates between the two groups. Furthermore, when applying an estimation rule developed for the sleep parameters measured by the FS-750, no differences were found in the average values between the calculated scores and PSG results, and we also observed a correlation between the two sets of results. Thus, the validity of these evaluation indices based on measurements from the FS-750 is confirmed.

CONCLUSIONS

The developed algorithm could determine sleep/wake states from activity intensity data obtained with the FS-750 with sensitivity and specificity equivalent to that determined with conventional actigraphs. The FS-750, which is smaller, less expensive, and able to take measurements over longer periods than conventional devices, is a promising tool for advancing sleep studies at home and in remote sleep medicine.

Examination of wrist and hip actigraphy using a novel sleep estimation procedure ☆

Objective

Improving and validating sleep scoring algorithms for actigraphs enhances their usefulness in clinical and research applications. The MTI^® device (ActiGraph, Pensacola, FL) had not been previously validated for sleep. The aims were to (1) compare the accuracy of sleep metrics obtained via wrist- and hip-mounted MTI^® actigraphs with polysomnographic (PSG) recordings in a sample that included both normal sleepers and individuals with presumed sleep disorders; and (2) develop a novel sleep scoring algorithm using spline regression to improve the correspondence between the actigraphs and PSG.

Methods

Original actigraphy data were amplified and their pattern was estimated using a penalized spline. The magnitude of amplification and the spline were estimated by minimizing the difference in sleep efficiency between wrist- (hip-) actigraphs and PSG recordings. Sleep measures using both the original and spline-modified actigraphy data were compared to PSG using the following: mean sleep summary measures; Spearman rank-order correlations of summary measures; percent of minute-by-minute agreement; sensitivity and specificity; and Bland–Altman plots.

Results

The original wrist actigraphy data showed modest correspondence with PSG, and much less correspondence was found between hip actigraphy and PSG. The spline-modified wrist actigraphy produced better approximations of interclass correlations, sensitivity, and mean sleep summary measures relative to PSG than the original wrist actigraphy data. The spline-modified hip actigraphy provided improved correspondence, but sleep measures were still not representative of PSG.

Discussion

The results indicate that with some refinement, the spline regression method has the potential to improve sleep estimates obtained using wrist actigraphy.

Diurnal 24-Hour Rhythm in Ambulatory Heart Rate Variability during the Day Shift in Rotating Shift Workers

Circadian variation in cardiac autonomic nervous system activity and behavior during the day shifts of shift workers has not hitherto been clarified. This study examined diurnal 24-h variation in heart rate variability (HRV), sleep-wake cycle, physical activity, and food intake during the day shift in rotating shift workers. The subjects were female nurses and caregivers working at a health care facility (14 day workers and 13 rotating shift workers). Each subject was asked to undergo 24-h electrocardiograph and step count recordings. Coarse graining spectral analysis was used for approximately 10-min segments of HRV (600 beats) to derive the total power (TOT: >0.04 Hz), integrated power in the low-frequency (LF: 0.04-0.15 Hz) and high-frequency (HF: >0.15 Hz) ranges, the ratio of HF power to TOT (HF nu), and the ratio of LF power to HF power (LF/HF). Double cosinor analysis was used to obtain 24-h and 12-h period variations in variables of HRV and physical activity. While no difference was found in the acrophases of either period for step counts or in the 12-h period of HRV variables between the groups, the acrophases of the 24-h period for HRV variables were delayed by 1.3 to 5.5 h in rotating shift workers, and their differences in HF power, HF nu, and LF/HF reached a significant level ( p < 0.05). On the days of the experiment, retiring time, waking up time, total time in bed, sleep efficiency, and mealtimes and energy intake for each diet did not differ between the groups. These results suggest that there is a possibility of an abnormal phase angle between circadian variation in cardiac autonomic nervous system activity and the sleep-wake cycle during the day shift in shift workers.

Automatic sleep/wake scoring from body motion in bed: validation of a newly developed sensor placed under a mattress

The purpose of this study was to formulate a "sleep/wake" scoring algorithm for processing activity measurements obtained using a newly developed nonwear actigraphy (NWA) device, and to test its validity. The NWA device has a highly sensitive pressure sensor and is placed under a mattress. It can continuously record the activity of a person lying on the mattress and identify an "in-bed/out-of-bed" state from the vibrations of the mattress. We formulated the sleep/wake scoring algorithm by using data obtained simultaneously by wrist actigraphy (Act) and the NWA device in 33 healthy participants. Agreement rate, sensitivity, and specificity with Act were 95.7%, 97.6%, and 75.8% (33 healthy people); the corresponding values were 85.9%, 89.1%, and 79.8% for 12 nursing home residents and 93.7%, 97.2%, and 60.8% for 60 nights for 6 healthy persons who slept 10 nights on their futons. Agreement rate, sensitivity, and specificity with polysomnography were in almost perfect agreement with Act (12 nights; 6 healthy persons who slept 2 nights). All our validation results indicate that the NWA device, placed under a mattress or a futon, can produce almost identical sleep/wake scores to Act. It is expected that the NWA device, a nonwear device for scoring sleep/wake and in-bed/out-of-bed, enables convenient long-term sleep-related evaluation in various fields, including hospital settings, home-care settings, and care facility settings such as nursing homes.

Sleep-related problems and use of hypnotics in inpatients of acute hospital wards

OBJECTIVE

Although sleep disorders are highly prevalent among patients with physical disorders, only limited information is available about the actual status of sleep-related problems in inpatients of acute hospital wards. We conducted a multicenter cross-sectional observational survey investigating the prevalence of sleep disorders and use of hypnotic-sedative drugs among inpatients of acute wards in 44 general hospitals in Japan.

METHOD

Questionnaire-, actigraph- and observation-based sleep evaluations were simultaneously performed in 557 adult inpatients [mean age 72.8 + or - 12.8 (S.D.) years] of acute wards during a one-month period in July 2007.

RESULTS

Of the 421 patients with data available, 22.3% had at least one of the following sleep disorders: sleep apnea syndrome, restless legs syndrome, periodic limb movement disorder and nocturnal behavior disorder. Similarly, 62.7% had insomnia, 6.9% had severe daytime sleepiness and 12.8% had other sleep-related symptoms. Only 13.8% were free of any sleep-related problem. Although 33.7% of insomnia patients were taking hypnotic-sedative drugs, 65.2% of them complained of residual insomnia symptoms.

CONCLUSION

The findings obtained in this study have revealed the remarkably high prevalence of sleep-related problems experienced by inpatients of acute hospital wards in Japan. Proper diagnosis of sleep disorders should be made among patients with physical disorders.