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STUDY OBJECTIVES: Whether the association between sleep-disordered breathing (SDB) and cardiovascular disease is independent of comorbid risk factors for cardiovascular disease is controversial. The objective of this study was to elucidate whether the association between SDB severity and the surrogate markers of cardiovascular disease events differs in relation to the number of comorbidities. METHODS: This cross-sectional study included 7,731 participants. Severity of SDB was determined by the oxygen desaturation index adjusted by actigraph-measured objective sleep time. Participants were stratified according to SDB severity and the number of comorbidities (hypertension, diabetes, dyslipidemia, and obesity), and the associations between the maximum value of intima-media thickness of the common carotid artery (CCA-IMT-max), brachial-ankle pulse wave velocity, and cardio-ankle vascular index were evaluated. RESULTS: Among participants with no risk factors, CCA-IMT-max increased according to SDB severity (n = 1022, P < .0001). Even after matching the background, the median CCA-IMT-max value was 14% higher in moderate-severe SDB patients than those without SDB (n = 45 in each group, P = .020). The difference was not significant for brachial-ankle pulse wave velocity and cardio-ankle vascular index. On the other hand, a significant difference in CCA-IMT-max was not found in those with multiple comorbidities. Consistently, multiple regression analysis revealed an independent association between CCA-IMT-max and moderate-severe SDB for all study participants (β: 0.0222, 95% confidence interval: 0.0039–0.0405, P = .017), but the association was not significant for stratified participants with multiple comorbidities. CONCLUSIONS: SDB severity is associated with the CCA-IMT-max level, but the independent association becomes weaker for those with multiple comorbidities. CITATION: Nakatsuka Y, Murase K, Matsumoto T, et al. Markers of cardiovascular disease risk in sleep-disordered breathing with or without comorbidities: the Nagahama Study. J Clin Sleep Med. 2021;17(12):2467–2475.

Recently an association between blood glucose dysregulation and sleep disruption was suggested. The association between sleep disordered breathing, most of which is due to obstructive sleep apnea (OSA) in the general population, and diabetic severity, as well as the impact of antidiabetic treatment, remains unclear. This study aimed to investigate these associations as well as age and sex differences. This cross-sectional study evaluated 7,680 community participants as the main cohort (population-based cohort). OSA was assessed by the 3% oxygen desaturation index from pulse oximetry, which was corrected for sleep duration obtained by wrist actigraphy. For arguing the limitations for using pulse oximetry, 597 hospitalised patients, who were assessed by the apnea-hypopnea index from attended polysomnography, were also evaluated as the validation cohort (hospital-based cohort). Moderate-to-severe OSA was more prevalent as haemoglobin A1c (HbA1c) levels increased (5.6%/5.6%-6.5%/6.5%-7.5%/≥7.5%, respectively) in both cohorts (p 0.001), but only in those without antidiabetic treatment. The HbA1c level was an independent factor for moderate-to-severe OSA (population-based cohort, odds ratio [OR] 1.26, 95% confidence interval [CI] 1.10-1.45; hospital-based cohort, OR 1.69, 95% CI 1.22-2.33, per 1% increase). These associations were more prominent in the middle-aged (aged60 years) than in the elderly (aged ≥60 years) and in women than in men in both cohorts. The prevalence of moderate-to-severe OSA in patients with antidiabetic treatment in the hospital-based cohort was ≥75% regardless of HbA1c levels. In conclusion, an association between the prevalence of OSA and HbA1c level even within or over the normal range was found only in patients without antidiabetic treatment and was more prominent in the middle-aged and in women.

[Objective] This study examined seasonal differences in continuous positive airway pressure (CPAP) therapy adherence among patients with obstructive sleep apnea (OSA). [Methods] Patients aged ≥20 years with OSA who had used CPAP devices on the automatic setting for >12 consecutive months (n = 141) were included in this retrospective study from December 2015–2016. The information of CPAP use (pressure, hours of actual use) was extracted from database downloaded from patients’ CPAP devices. Patients were divided into adherent and non-adherent groups using the cutoff point of 70% CPAP use for ≥4 h daily over the 1-year study period. CPAP use data were averaged for each season. [Results] Patients in the adherent group were significantly older than those in the non-adherent group (p < 0.001). In the adherent group, the rate of ≥4 h daily CPAP use was significantly lower, the daily duration of CPAP use was significantly shorter, and the residual apnea–hypopnea index (AHI; events/hour) was significantly higher in summer than in other seasons (all p < 0.001). In the non-adherent group, the duration of daily CPAP use and the AHI differed significantly between winter and summer (p = 0.008 and p < 0.001, respectively). [Conclusions] Seasonal changes were associated with the CPAP adherence of patients with OSA. The study findings suggest that there is possibility of increasing the duration of CPAP use by adjusting the bedroom environment in hot and humid seasons.

STUDY OBJECTIVES: Since subjective sleep duration (SSD) is considered to be longer than objective sleep duration (OSD), results of SSD minus OSD (SSD−OSD) might always be thought to be positive. Some recent reports showed different results, but exact results have not been obtained. The difference between SSD and OSD may change according to OSD. We investigated this difference and its association with sleep-disordered breathing (SDB) or nonrestorative sleep. METHODS: This cross-sectional study evaluated 6,908 community residents in Nagahama, Japan. SSD was determined by self-administered questionnaire. OSD was measured by wrist actigraphy and sleep diary. SDB was assessed according to the 3% oxygen desaturation index adjusted for OSD. RESULTS: Worthy of notice was that SSD was shorter than OSD for those with SSD longer than 6.98 hours in all participants, 7.36 hours in males, and 6.80 hours in females. However, SSD was longer than OSD (mean ± SD: 6.49 ± 1.07 vs 6.01 ± 0.96; P < .001) overall, as SSD is considered to be longer than OSD. In patients with SDB, the difference between SSD−OSD was greater when OSD was shorter. The difference also depended on SDB severity. The degree of positivity between OSD and SSD was a significant factor in nonrestorative sleep (odds ratio: 2.691; P < .001). CONCLUSIONS: When OSD was slightly less than 7 (6.98) hours, participants reported or perceived SSD > OSD. When OSD was > 6.98 hours, participants reported or perceived SSD < OSD. Patients with SDB reported longer SSD than OSD according to severity of SDB. Evaluating SSD, OSD, and their differences may be useful for managing sleep disturbances, including nonrestorative sleep. CITATION: Takahashi N, Matsumoto T, Nakatsuka Y, et al. Differences between subjective and objective sleep duration according to actual sleep duration and sleep-disordered breathing: the Nagahama Study. J Clin Sleep Med. 2022;18(3):851–859.

BACKGROUND High sleep blood pressure (BP) has been suggested to be an independent risk factor for cardiovascular outcomes. To assess the applicability of sleep BP measured using a timer-equipped home device, we investigated the association between home device-measured sleep BP and large artery stiffness. METHODS We performed a cross-sectional analysis of a dataset from the Nagahama study (N = 5916), a general population-based cohort study. Home morning BP and sleep BP were measured using a timer-equipped cuff-oscillometric device (HEM-7080IC). Office BP, carotid intima--media thickness (IMT), and brachial--ankle pulse wave velocity (baPWV) were measured at the follow-up investigation of the Nagahama study. RESULTS Sleep hypertension (SBP ≥120 mmHg and/or DBP ≥70 mmHg) was associated with the arterial parameters (IMT: β = 0.051, baPWV: β = 0.141, both P

Rationale: Although sleep disordered breathing (SDB) may increase urinary albumin excretion (UAE) by raising nocturnal blood pressure (BP) in addition to diurnal BP, the correlation has not been in...

BACKGROUND Nocturia is a risk factor for poor quality of life and increased mortality. This study was aimed to clarifying dietary habits, eating behaviors, and sleep characteristics associated with nocturia to identify modifiable lifestyle factors for nocturia. METHODS This cross-sectional study included 5683 community residents (64.5 ± 7.7 years old). The frequency of nocturnal urination was recorded for 1 week using a sleep diary. The frequency of food intake, unfavorable eating behaviors, and sleep characteristics that may have influence on salt intake and wasting were obtained using a structured questionnaire. RESULTS The frequency of nocturnal urination was increased with age (β = .312, P

In humans, most renal functions, including urine volume and electrolyte excretions, have a circadian rhythm. Light is a strong circadian entrainment factor and daytime-light exposure is known to affect the circadian rhythm of rectal temperature (RT). The effects of daytime-light exposure on the diurnal rhythm of urinary excretion have yet to be clarified. The aim of this study was to clarify whether and how daytime exposure to bright-light affects urinary excretions. Twenty-one healthy men (21–27 years old) participated in a 4-day study involving daytime (08:00–18:00 h) exposure to two light conditions, Dim (p = 0.017) and sodium (Na), chloride (Cl), and uric acid (UA) excretion and urine volumes were greater (all p

STUDY OBJECTIVES: It is well known that a family history of diabetes (FHD) is a definitive risk factor for type 2 diabetes. It has not been known whether sleep-disordered breathing (SDB) increases the prevalence of diabetes in those with an FHD. METHODS: We assessed SDB severity in 7,477 study participants by oximetry corrected by objective sleep duration determined by wrist actigraphy. Glycated hemoglobin ≥6.5% and/or current medication for diabetes indicated the presence of diabetes. In addition to the overall prevalence, the prevalence of recent-onset diabetes during the nearly 5 years before the SDB measurements were made was investigated. RESULTS: Of the 7,477 participants (mean age: 57.9; range: 34.2–80.7; SD: 12.1 years; 67.7% females), 1,569 had an FHD. The prevalence of diabetes in FHD participants with moderate-to-severe SDB (MS-SDB) was higher than in those without SDB (MS-SDB vs without SDB: all, 29.3% vs 3.3% [P < .001]; females, 32.6% vs 1.9% [P < .001]; males, 26.2% vs 11.7% [P = .037]). However, multivariate analysis showed that MS-SDB was significantly associated with a higher prevalence of diabetes only in FHD-positive females (odds ratio [95% confidence interval]: females, 7.43 [3.16–17.45]; males, 0.92 [0.37–2.31]). Among the FHD-positive participants, the prevalence of recent-onset diabetes was higher in those with MS-SDB than those without SDB, but only in females (MS-SDB vs without SDB: 21.4% vs 1.1%; P < 0.001). CONCLUSIONS: MS-SDB was associated with diabetes risk in females with an FHD, and future studies are needed on whether treatment of SDB in females with an FHD would prevent the onset of diabetes. CITATION: Minami T, Matsumoto T, Tabara Y, et al. Impact of sleep-disordered breathing on glucose metabolism among individuals with a family history of diabetes: the Nagahama study. J Clin Sleep Med. 2021;17(2):129–140.

Background: While self-reported subjective sleep duration (SSD) usually tends to exceed actual sleep duration (objective sleep duration, OSD), factors related to the differences between SSD and OSD are unknown. It was reported that sleep disordered breathing (SDB) altered the perception of sleep habits. Aims and Objectives: This study aimed to compare SSD with OSD and to examine whether SDB was related to the differences between SSD and OSD. Methods: This cross-sectional study evaluated 6908 community residents in Nagahama city, Japan. SSD was determined by a self-administered questionnaire while OSD was measured by wrist actigraphy and a sleep diary. SDB was assessed according to the 3% oxygen desaturation index modified for OSD obtained by actigraphy. Results: In groups of participants with SSD Conclusions: OSD tended to be longer than SSD in those who reported short SSD, while the opposite occurred in those reporting long SSD; however, this tendency was offset at 5.7 hours. OSD was shorter than SSD as the severity of SDB increased. These data will help to better assess patients’ complaints about sleep duration.

Sleep-disordered breathing (SDB) is a well-known risk factor for cardiovascular outcomes. Studies of patients with SDB have identified frequent night-time urination as a manifestation related to SDB. We aimed to clarify whether night-time frequency of urination is independently associated with SDB in a general population. We also investigated whether night-time frequency of urination can help presumptive diagnose SDB.Study participants consisted of 7151 community residents. Oxygen saturation during sleep was measured for four nights using a pulse oximeter. SDB was defined as ≥15 events per hour in which oxygen desaturation exceeded or equal to 3% during an actigraphy-determined sleep period. Night-time frequency of urination was recorded for one week using a sleep diary.Significant positive correlations were evident between night-time frequency of urination and SDB (none, 5.8%; once/night, 14.1%; twice/night, 20.1%; thrice/night, 28.7%;thrice/night, 44.1%, P 0.001). This association was independent of possible covariates, including sleep duration (adjusted odds ratio: once/night = 1.50, twice/night = 2.15, thrice/night = 3.07,thrice/night = 3.73, P 0.001). Other factors significantly associated with SDB were age, sex, obesity, observation of sleep apnea, and short sleep duration. The area under the curve of the risk score for SDB consisting of these conventional six items (0.834) significantly improved (0.842, P = 0.001) when night-time frequency of urination was considered as a risk score item.Night-time frequency of urination was associated with SDB. Our findings suggest that the urination frequency should be considered a manifestation of SDB even in a general population.

Abnormalities in circadian blood pressure (BP) variation, particularly increase in nocturnal BP, have been reported to be risk factors for cardiovascular disease, although the factors associated with BP abnormalities are not fully understood. This study aimed to clarify possible associations of sleep characteristics, including sleep fragmentation, sleep disordered breathing, and nocturia, with sleep BP by simultaneous multiday measurements.A cross-sectional study evaluated 5959 community participants having home-measured data on nocturnal BP change (sleep BP - awaking BP), sleep characteristics, and sleep disordered breathing. Sleep characteristics including the fragmentation index were assessed using wrist-wearable actigraphy, whereas sleep disordered breathing was assessed by 3% oxygen desaturation index obtained using a finger-type monitor. The number of nocturnal urinations was recorded in a sleep diary.Mean nocturnal SBP change was -8.5 ± 7.9%. A 3% oxygen desaturation index was associated with the BP change independently of the basic covariates (β = 0.051, P = 0.001), although the association became insignificant (P = 0.196) after adjusting the fragmentation index (β = 0.105, P 0.001). The association of the fragmentation index was also insignificant (P = 0.153) after adjusting measurement season (middle season: β = 0.163, P 0.001; summer season: β = 0.249, P 0.001). In contrast, the frequency of urination showed strong and independent association (β = 0.140, P 0.001), with smaller nocturnal BP drop in participants with frequent urination.Subjective sleep estimates and frequent nocturnal urination may represent a potential risk for circadian BP abnormalities.

High sodium intake is a simple modifiable risk factor for hypertension. Although not confirmed, lower socioeconomic status may be a factor that increases sodium intake. We aimed to clarify the association between socioeconomic status and urinary sodium-to-potassium ratio by cross-sectional and longitudinal analyses. The study included 9410 community residents. Spot urine sodium-to-potassium ratios were measured twice with a 5-year interval. Socioeconomic status was investigated using a self-administered questionnaire. Cross-sectional analysis revealed that educational attainment was inversely associated with urinary sodium-to-potassium ratio (years of education ≤ 9: 3.0 ± 1.8, ≤ 12: 2.9 ± 1.6, ≥ 13: 2.8 ± 1.6; P

The guidelines for night and shift workers recommend that after night work, they should sleep in a dark environment during the daytime. However, staying in a dark environment during the daytime reduces nocturnal melatonin secretion and delays its onset. Daytime bright-light exposure after night work is important for melatonin synthesis the subsequent night and for maintaining the circadian rhythms. However, it is not clear whether daytime sleeping after night work should be in a dim- or a bright-light environment for maintaining melatonin secretion. The aim of this study, therefore, was to evaluate the effect of bright-light exposure during daytime sleeping on nocturnal melatonin secretion after simulated night work. Twelve healthy male subjects, aged 24.8 ± 4.6 (mean ± SD), participated in 3-day sessions under two experimental conditions, bright light or dim light, in a random order. On the first day, the subjects entered the experimental room at 16:00 and saliva samples were collected every hour between 18:00 and 00:00 under dim-light conditions. Between 00:00 and 08:00, they participated in tasks that simulated night work. At 10:00 the next morning, they slept for 6 hours under either a bright-light condition (3000 lx) or a dim-light condition (50 lx). In the evening, saliva samples were collected as on the first day. The saliva samples were analyzed for melatonin concentration. Activity and sleep times were recorded by a wrist device worn throughout the experiment. In the statistical analysis, the time courses of melatonin concentration were compared between the two conditions by three-way repeated measurements ANOVA (light condition, day and time of day). The change in dim light melatonin onset (ΔDLMO) between the first and second days, and daytime and nocturnal sleep parameters after the simulated night work were compared between the light conditions using paired t-tests. The ANOVA results indicated a significant interaction (light condition and3 day) (p = .006). Post hoc tests indicated that in the dim-light condition, the melatonin concentration was significantly lower on the second day than on the first day (p = .046); however, in the bright-light condition, there was no significant difference in the melatonin concentration between the days (p = .560). There was a significant difference in ΔDLMO between the conditions (p = .015): DLMO after sleeping was advanced by 11.1 ± 17.4 min under bright-light conditions but delayed for 7.2 ± 13.6 min after sleeping under dim-light conditions. No significant differences were found in any sleep parameter. Our study demonstrated that daytime sleeping under bright-light conditions after night work could not reduce late evening melatonin secretion until midnight or delay the phase of melatonin secretion without decreasing the quality of the daytime sleeping. Thus, these results suggested that, to enhance melatonin secretion and to maintain their conventional sleep-wake cycle, after night work, shift workers should sleep during the daytime under bright-light conditions rather than dim-light conditions.

Light is the strongest synchronizer controlling circadian rhythms. The intensity and duration of light change throughout the year, thereby influencing body weight, food preferences, and melatonin secretion in humans and animals. Although the expression of clock genes has been examined using human samples, it currently remains unknown whether bright light during the daytime affects the expression of these genes in humans. Therefore, we herein investigated the effects of bright light exposure during the daytime on clock gene expression in the hair follicular and root cells of the human scalp. Seven healthy men (20.4 ± 2.2 years old; 172.3 ± 5.8 cm; 64.3 ± 8.5 kg; BMI 21.7 ± 3.1 kg/m2, mean ± SD) participated in this study. Subjects completed 3-day experimental sessions twice in 1 month during which they were exposed to bright and dim light conditions. The mRNA expression of Per1–3, Cry1–2, Rev-erb-α (Nr1d1), Rev-erb-β (Nr1d2), and Dec1 was analyzed using branched DNA probes. No significant changes were observed in the expression of Per1, Per2, Per3, Cry1, Cry2, Rev-erb-α (Nr1d1), or Dec1 following exposure to bright light conditions. However, the expression of Rev-erb-β (Nr1d2) tended to be stronger under bright light than dim light conditions. These results suggest that the bright light stimulus did not influence the expression of clock genes in humans. Long-lasting bright light exposure during the daytime may be required to change the expression of clock genes in humans.

It is well known that the prevalence of sleep disordered breathing (SDB) is increased in patients with obesity or metabolic comorbidities. However, the way in which the prevalence of SDB increases in relation to comorbidities according to the severity of obesity remains unclear.This cross-sectional study evaluated 7713 community participants using nocturnal oximetry ≥2 nights. SDB was assessed by the 3% oxygen desaturation index corrected for sleep duration obtained by wrist actigraphy (acti-ODI3%). SDB severity was defined by acti-ODI3%. Obesity was defined as body mass index ≥25 kg·m−2.The prevalence of SDB was 41.0% (95% CI 39.9–42.1%), 46.9% (45.8–48.0%), 10.1% (9.5–10.8%) and 2.0% (1.7–2.3%) in normal, mild, moderate and severe SDB, respectively, with notable sex differences evident (males>post-menopausal females>premenopausal females). Comorbidities such as hypertension, diabetes and metabolic syndrome were independently associated with the prevalence of moderate-to-severe SDB, and coincidence of any one of these with obesity was associated with a higher probability of moderate-to-severe SDB (hypertension OR 8.2, 95% CI 6.6–10.2; diabetes OR 7.8, 95% CI 5.6–10.9; metabolic syndrome OR 6.7, 95% CI 5.2–8.6). Dyslipidaemia in addition to obesity was not additively associated with the prevalence of moderate-to-severe SDB. The number of antihypertensive drugs was associated with SDB (p for trend Metabolic comorbidities contribute to SDB regardless of the degree of obesity. We should recognise the extremely high prevalence of moderate-to-severe SDB in patients with obesity and metabolic comorbidities.

Nocturia in older adults has been reported to be a risk factor for cardiovascular outcomes, and the stiffening of large arteries might be an underlying mechanism. To clarify the possible association between nocturia and arterial stiffness, we analyzed a dataset from the Japanese general population. Study participants consisted of 5928 community residents (mean age: 60.0 ± 11.8 years). The frequency of nocturnal urination was recorded for 1 week using a sleep diary. Arterial stiffness was assessed by brachial-to-ankle pulse wave velocity (baPWV). Sleep blood pressure was measured automatically at 0000, 0200, and 0400 hours by wearing a cuff on the upper arm during sleep. The mean baPWV was 1278 ± 227 cm/s. The frequency of nocturnal urination showed a linear positive association with baPWV (P 0.001). The association between a sleep diary-based nocturnal urination frequency 1.5 times/night (corresponding to a ≥ 2 times/night frequency obtained by the questionnaire) and baPWV remained significant after adjusting for major covariates, including office blood pressure (β = 0.051, P 0.001) and sleep blood pressure (β = 0.040, P 0.001). This association was more prominent in men (β = 0.069, P 0.001) than in women (β = 0.023, P = 0.013), particularly in older (β = 0.068, P = 0.006) compared with younger (β = 0.029, P = 0.270) men. Frequent nocturnal urination was independently associated with baPWV in older men. Nocturia may be a marker for cardiovascular disease risks that cannot be assessed by conventional risk factors such as blood pressure.

Nocturia is a common phenomenon in older individuals, and is associated with poor quality of life. Nocturia is a multifactorial disorder, wherein the frailty of skeletal muscles, particularly muscle weakness in the lower trunk and hip regions, might be a risk factor in women. We analyzed a dataset of the general Japanese population to clarify the hypothesis.Study participants included 1207 older women (mean age 67.4 ± 5.2 years). The frequency of nocturnal urination was assessed using a sleep diary for 1 week, and associations with lower muscle strength, skeletal muscle index, sarcopenia and physical performance (one-leg standing time and Timed Up and Go test) were investigated.The frequency of nocturnal urination more than one voiding per night was 28.1%; this frequency was inversely associated with hip abduction strength quartiles (Q1: 37.0, Q2: 30.5, Q3: 25.1 and Q4: 19.9%, P 0.001). When a sleep diary-based nocturnal urination frequency 1.5 times/night (corresponding to a ≥2 times/night frequency obtained by questionnaire) was considered as nocturia, logistic regression analysis adjusted for major covariates identified hip abduction strength as an independent inverse determinant of nocturia (odds ratio 0.75, 95% CI 0.52-0.90, P = 0.002). In contrast, no significant association was observed with knee extension (P = 0.322) and hip flexion (P = 0.603) strengths. Physical performance, skeletal muscle index and sarcopenia did not show significant associations with nocturia.Weak hip abduction strength might be a factor associated with nocturnal urination frequency in older women. Geriatr Gerontol Int 2019; 19: 1010-1016.

The sodium-to-potassium ratio (Na/K) of a urine sample is a simple index of salt loading. To practically use Na/K, we aimed to determine whether the Na/K value affects blood pressure (BP) at any age, irrespective of urinary Na and K levels. We analyzed a dataset of the general population (the Nagahama study), including baseline and second-visit measurements performed 5 years after the baseline. Spot urine samples were used for Na/K assessments. A total of 18,505 observations were analyzed using a linear mixed model, including the measurement term as a random effect. Urinary Na/K values showed a positive association with BP. When the highest quartile of Na/K was further divided by the urinary Na/creatinine (Cre) and K/Cre levels, the high-Na/Cre (3.58) and high-K/Cre (0.75) (Na/K = 4.80) groups, as well as the low Na/Cre (1.23) and low-K/Cre (0.26) (Na/K = 4.87) groups, exhibited similar effects on systolic BP (6.82 mmHg [95% CI: 5.72–7.92] and 6.63 mmHg [95% CI: 5.35–7.91], respectively). A similar association was observed in other Na/K quartiles. The positive association of Na/K and Na/Cre with BP was steeper in the older groups, while the inverse association of K/Cre was predominant in the younger population. The results of the multivariate analysis identified interaction terms between age and Na/K, Na/Cre and K/Cre as significant determinants for SBP. The positive association of urinary Na/K with BP was independent of the urinary Na and K levels. The association between Na/K and BP may not be uniform across ages by decade.

We aimed to analyze associations of sleep disturbance, including sleep disordered breathing, sleep fragmentation, and sleep efficiency, with abnormal nocturnal blood pressure (BP) profiles that may be risk factors for adverse cardiovascular outcomes.The study included 5854 community residents with 20,725 multi-day measurements. Sleep fragmentation and efficiency were evaluated using a wrist-worn activity monitor. Sleep disordered breathing was assessed using the 3% oxygen desaturation index corrected for actigraphy-determined sleep duration. A timer-equipped standard cuff-oscillometric device was used for home and sleep BP monitoring.Mean nocturnal systolic BP (SBP) change was -8.6 ± 9.7% (-11.1 ± 12.6 mmHg), and inter-day correlation coefficient of the nocturnal SBP change was 0.443. Results of a linear mixed model analysis using daily measured values identified lower sleep efficiency (coefficient = -0.130, p 0.001) as a determinant for decreased nocturnal SBP dipping beyond the interday variations of these parameters. Number of nocturnal urinations was another strong determinant (coefficient = 1.191, p 0.001), although the association of sleep efficiency was independent of nocturnal urination, awake SBP, and sleep disordered breathing (coefficient = -0.102, p 0.001). Sleep efficiency was also independently associated with sleep SBP level (coefficient = -0.138, p 0.001). Estimated differences in nocturnal SBP dipping and sleep SBP level as a function of the degree of sleep efficiency (less than 80%) reached 1.63% (1.09-2.17%) and 2.16 mmHg (1.49-2.82%), respectively.More attention should be paid to sleep efficiency as a factor in maintaining circadian BP rhythm.

BACKGROUND The aim of this study is to clarify associations between orthostatic blood pressure (BP) change, as well as possible physiological factors, and day-to-day home BP variability, a promising risk factor for cardiovascular outcomes. METHODS Study participants were 6,465 community residents (age 58.3 years). Home BP was measured every morning and evening for 7 days. Orthostatic BP was calculated as the maximum difference between BP measured while sitting and remeasured after 1 and 3 minutes standing. RESULTS Frequency of individuals who showed orthostatic BP decline was as follows: systolic BP (SBP) change ≥−20 mm Hg: 2.6%, ≥−10 mm Hg: 14.1%. These subgroups showed larger home SBP variability (average real variability: 11.3 ± 5.3, 8.7 ± 3.9 mm Hg) when compared with orthostatic normotensives (7.6 ± 3.7 mm Hg) (all P < 0.001). Multiple linear regression analysis adjusted for major covariates, including seated BP, identified orthostatic BP drop as an independent determinant for morning BP variability (≥−20 mm Hg: β = 0.037, P = 0.003; ≥−10 mm Hg: β = 0.026, P = 0.036) but not for evening BP variability. Carotid hypertrophy was significantly associated with home BP variability (morning: β = 0.052, P = 0.001; evening: β = 0.065, P < 0.001) and showed a U-shaped association with orthostatic BP change. Plasma B-type natriuretic peptide level, a previously suggested factor for BP variability, did not show significant association with morning and evening BP variability. CONCLUSION Orthostatic BP decline was significantly associated with morning BP variability. Large artery atherosclerosis was a common risk factor.

Study Objectives The individual prevalence of sleep-disordered breathing (SDB), short sleep duration, and obesity is high and increasing. The study aimed to investigate potential associations between SDB, objective sleep duration, obesity, diabetes and hypertension across genders, and the effect of pre- or post-menopausal status. Methods A cross-sectional study evaluated 7051 community participants with wrist actigraphy for a week, and nocturnal oximetry ≥ 2 nights. SDB was assessed by 3 per cent oxygen desaturation index (ODI) corrected for sleep duration obtained from wrist actigraphy. Moderate-to-severe SDB was defined as ODI3% levels ≥ 15 per hour. Results Both logODI3% and body mass index showed independent negative associations with sleep duration (β = -0.16, p < 0.001 and β = -0.07, p < 0.001, respectively). Moderate-to-severe SDB (men/premenopausal women/postmenopausal women; 23.7/1.5/9.5%, respectively) was associated with a higher risk of diabetes in premenopausal women (OR 28.1; 95%CI 6.35-124.6; p < 0.001) and postmenopausal women (OR 3.25; 95%CI 1.94-5.46; p < 0.001), but not in men (OR 1.47; 95%CI 0.90-2.40; p = 0.119). Moderate-to-severe SDB was associated with a higher risk of hypertension in men (OR 3.11; 95%CI 2.23-4.33; p < 0.001), premenopausal women (OR 3.88; 95%CI 1.42-10.6; p = 0.008), and postmenopausal women (OR 1.96; 95%CI 1.46-2.63; p < 0.001). Short sleep duration was not associated with diabetes or hypertension. The associations of obesity with diabetes or hypertension were indirectly mediated by SDB (24.0% and 21.5%, respectively), with possible sex differences emerging (men/women; 15.3/27.8% and 27.0/16.9%, respectively). Conclusions Notwithstanding the cross-sectional design, SDB and obesity, but not short sleep duration, were independently associated with diabetes and hypertension, with gender and menopausal status-related differences in risk emerging.

Backgrounds: Abnormalities in circadian blood pressure (BP) variation have been suggested to be associated with cardiovascular diseases and mortality. Factors affecting the variability need to be clarified to precisely evaluate the risk of circadian BP abnormalities. Given the seasonal differences in casual BP, it was hypothesized that nocturnal BP may also differ by season. Here we aimed to clarify seasonal and day-by-day variability of circadian BP variation in a large-scale general population. Methods: We analyzed a dataset describing in the Nagahama study. Study participants were 4,792 community residents. Evening, sleep, and morning BP values were measured for 5 days at home using an automatic cuff-oscillometric device (HEM-7080IC). Participants were required to sleep with putting a cuff on the upper arm. The BP monitor was programmed to automatically measure BP at 0, 2, and 4 o’clock, and all readings were recorded in a built-in memory of the device. Sleeping period was objectively defined by actigraphy. Results: Overall frequency of extreme-dipper, dipper, non-dipper, and riser were 6.5, 34.9, 45.1, and 13.5%, respectively. Nocturnal systolic BP fall was significantly smaller in individuals whose BP was measured during the summer season (summer, –5.8 ± 7.8%; middle, –8.2 ± 7.5%; winter, –11.1 ± 7.7%; p p p p Conclusion: Nocturnal BP fall was largely different by season with higher frequency of riser and non-dipper in summer. The seasonality might not be due to the seasonal difference in day-by-day variability of nocturnal BP changes.

Abnormalities in circadian blood pressure (BP) variation have been suggested to be associated with cardiovascular diseases and mortality. Factors affecting this variability need to be clarified to precisely evaluate the risk of circadian BP abnormalities. Given the seasonal differences in casual BP, it was hypothesized that nocturnal BP may also differ by season. Here, we aimed to clarify the seasonality of circadian BP variation, as well as the factors associated with this seasonality, in a large-scale general population (n = 4780). This is a cross-sectional study based on multiday BP values measured in the evening, during sleep, and in the morning. Measurements were taken at home using an automatic cuff-oscillometric device. The sleeping period was objectively defined by actigraphy. The nocturnal systolic BP fall was significantly less in individuals whose BP was measured during the summer season (summer, −5.8 ± 7.8%; middle (spring or autumn), −8.2 ± 7.5%; winter, −11.0 ± 7.7%; p

Background Tryptophan (TRP) is an essential amino acid, and it has been suggested that TRP intake at breakfast combined with daytime bright light exposure can increase nocturnal melatonin secretion. However, the mechanisms involved are not yet clear. The aim of this study was to examine the effect of TRP supplement intake at breakfast on nocturnal melatonin secretion under different daytime light intensities in humans. Method Twelve subjects (aged 21.3 ± 3.0 years, mean ± standard deviation) participated in a random order in experimental sessions lasting 3 days under four conditions in a laboratory setting. The four conditions were TRP*Bright, Placebo*Bright, TRP*Dim, and Placebo*Dim. A TRP capsule (1000 mg) or a placebo starch capsule (1000 mg) were taken at breakfast. In addition, during the daytime (07:00–18:00), the subjects were asked to stay under different light intensities: >5000 lx (bright) or

Background: There are few reports about sleep disturbances in patients with chronic obstructive pulmonary disease (COPD) in Asian countries. Objectives: To investigate the associations between sleep-disordered breathing (SDB) with hypoxemia and sleep quality, including sleep duration, in patients with COPD, we measured SDB and sleep quality including the objective sleep duration determined by an actigraph and portable monitoring. Methods: A cross-sectional epidemiological health survey of 303 male employees (means ± SD: age 43.9 ± 8.2 years; BMI 24.0 ± 3.1) was conducted. Sleep quality was measured using the Epworth Sleepiness Scale (ESS) and the Pittsburgh Sleep Quality Index (PSQI). A respiratory disturbance index (RDI) ≥5 indicated SDB. Results: Nineteen subjects (6.3%) had COPD. Among these, 11 (3.6%) had COPD with SDB (overlap syndrome). Sleep duration, ESS, and PSQI scores were not significantly different between COPD patients and normal control subjects. However, COPD patients had significantly longer sleep latency (p = 0.019), a lower sleep efficiency (p = 0.017), and a higher sleep fragmentation index (p = 0.041) and average activity (p = 0.0097) during sleep than control subjects. They also had a significantly higher RDI and more severe desaturation during sleep than control subjects (p < 0.01). The differences remained after adjustment for age and BMI but disappeared following adjustment for RDI. Conclusions: COPD patients with even mild-to-moderate airflow limitations had nocturnal desaturation and RDI-related impaired sleep quality without significant symptoms.

Dyslipidemia is often comorbid with obstructive sleep apnea (OSA), but few population-based studies have investigated their relationship. Short sleep duration is associated with hypertension and diabetes; however, its association with dyslipidemia is not well known. We investigated relationships among OSA, sleep duration, and the lipid profile in a community-based study.We measured the respiratory disturbance index (RDI) and sleep duration by a type 3 portable device and actigraph in 275 men in a Japanese company. Fasting blood parameters were obtained from periodic inspection data.According to Japanese criteria, 143 subjects had dyslipidemia. Percent sleep time of oxygen saturation as measured by pulse oximetry (SpO2)lt; 90% and prevalence of severe OSA were greater and sleep duration and mean SpO2 during sleep were lower in subjects with dyslipidemia than in those without. Univariate analysis showed that the RDI was positively correlated with serum triglyceride (TG) levels (ρ = 0.20, Plt; .01), and sleep duration was negatively correlated with serum total cholesterol (TC) levels (γ = -0.13, P = .03) and serum low-density lipoprotein cholesterol levels (γ = -0.12, P = .04). Stepwise multiple regression analysis revealed that TG was correlated with RDI (β = 0.14, P = .02), BMI (β = 0.20, Plt; .01), and alcohol intake (β = 0.20, Plt; .01), and that TC was correlated with sleep duration (β = -0.13, P = .03), age (β = 0.15, P = .02), and waist/hip ratio (β = 0.15, P = .02).Short sleep duration was associated with TC levels and RDI was positively associated with TG levels among working-aged men in an urban Japanese company. Correcting the status of OSA and/or short sleep duration might improve the lipid profile and cardiovascular consequences.

Obstructive sleep apnoea is common in patients with diabetes. Recently, it was reported that short sleep duration and sleepiness had deleterious effects on glucose metabolism. Thereafter, several reports showed relationships between glucose metabolism and obstructive sleep apnoea, sleep duration or sleepiness. But the interrelationships among those factors based on recent epidemiological data have not been examined. We analysed data on 275 male employees (age, 44±8years; body mass index, 23.9±3.1kg m(-2) ) who underwent a cross-sectional health examination in Japan. We measured fasting plasma glucose, sleep duration using a sleep diary and an actigraph for 7days, and respiratory disturbance index with a type 3 portable monitor for two nights. Fifty-four subjects (19.6%) had impaired glucose metabolism, with 21 having diabetes. Of those 21 (body mass index, 25.9±3.8kgm(-2) ), 17 (81.0%) had obstructive sleep apnoea (respiratory disturbance index≥5). Regarding the severity of obstructive sleep apnoea, 10, four and three had mild, moderate and severe obstructive sleep apnoea, respectively. The prevalence of obstructive sleep apnoea was greater in those with than without diabetes (P=0.037). Multiple regression analyses showed that the respiratory disturbance index independently related to fasting plasma glucose only in the diabetic subjects. In patients with diabetes, after adjustment for age, waist circumference, etc. sleep fragmentation had a greater correlation with fasting plasma glucose than sleep duration, but without significance (P=0.10). Because the prevalence of obstructive sleep apnoea is extremely high in patients with diabetes, sufficient sleep duration with treatment for obstructive sleep apnoea, which ameliorates sleep fragmentation, might improve fasting plasma glucose.

Obstructive sleep apnoea (OSA) plays a significant role in increasing blood pressure. Significant decreases were reported in blood pressure of hypertensive OSA patients with sleepiness who underwent continuous positive airway pressure (CPAP) treatment, but not in non-sleepy hypertensive OSA patients. More recently, however, significant decreases in blood pressure in non-sleepy hypertensive OSA patients following CPAP were shown. Effects of sleepiness on hypertension in OSA patients have been investigated, but not the effects of hypertension on sleepiness in OSA patients. We investigated the relationships between hypertension and sleepiness in patients with OSA. We analysed data on 275 middle-aged male subjects from a cross-sectional epidemiological health survey. We measured blood pressure and sleep duration objectively using an actigraph for 7 days and the respiratory disturbance index (RDI) with a type 3 portable device for 2 nights, and assessed sleepiness using the Epworth Sleepiness Scale (ESS). The RDI correlated significantly with ESS scores in the 88 hypertensive subjects (r = 0.33, P = 0.0024), but not in the 187 non-hypertensive subjects (r = -0.01, P = 0.91). Short sleep duration correlated significantly with ESS scores in both groups. Both the RDI and short sleep duration were related independently to sleepiness in only hypertensive subjects. Furthermore, the RDI was related negatively significantly to sleep duration in hypertensive subjects. Although short sleep duration was related significantly to sleepiness in both groups, hypertension may be important for the sleepiness in OSA patients. Detailed mechanisms of the difference in the relationship between sleepiness and the severity of OSA with or without hypertension should be studied further.

SLEEP-RELATED HEALTH PROBLEMS AND THEIR IMPACT ON SOCIETY AND ON INDIVIDUALS ARE A MAJOR SOCIAL ISSUE. PEOPLE WITH SLEEP-DISORDERED breathing (SDB) are at increased risk for hypertension,1,2 cardiovascular diseases,3 and mortality.3,4 However, SDB and obstructive sleep apnea syndrome (OSAS) are prevalent but largely undiagnosed in adults.5 In spite of this wide population of undiagnosed patients, in-laboratory sleep-recording capacity has remained limited. This current situation presents an urgent need to move toward the use of portable monitors in home settings. Epidemiologic studies for SDB and OSAS have been conducted not only in Western countries,1–5 but also in Asian countries.6,7 However, sound estimates of SDB prevalence in Japan are lacking: previous Japanese studies have been limited by use of nonprobability samples, low response rates, small samples, and other methodologic problems. All previous Japanese epidemiologic studies on SDB and OSAS were performed with type 4 portable monitors.8–10 In our current study, a cardiorespiratory monitoring device (also referred to as a type 3 portable monitoring device) was used together with actigraphy at home to analyze SDB. Type 3 portable monitors are defined as devices with a minimum of 4 channels monitored,11 including ventilation or airflow (at least 2 channels of respiratory movement or respiratory movement and airflow), heart rate or electrocardiogram, and oxygen saturation, whereas portable monitors that do not meet these criteria are designated as type 4.11 Attended type 3 sleep studies are thought to be a standard method and an alternative for polysomnography in the diagnosis and follow-up for SDB and OSAS.12 On the other hand, type 4 portable monitors are not recommended for diagnosis because they have a higher percentage of false-positive results and high rates of false negatives or conflicting results.11 Most epidemiologic studies have been performed with polysomnography in laboratory settings. Using in-laboratory polysomnography as the gold standard has limitations in validity, partly because subjects tend to sleep more poorly in the laboratory than at home.11 In this study, participants were asked to follow their usual lifestyles, and sleep recordings were performed at home. Home monitoring that more closely reflects the subjects' usual drinking and sleeping habits may present a different prevalence or different outcomes than those from previous reports in the laboratory settings. Recently, obesity has become a major social problem in Japan. The prevalence of obesity (body mass index: [BMI] ≥ 25) in 1983, 1993, and 2003 was 26.7%, 24.5% and 34.4%, respectively, among the Japanese male general population aged 40 to 49 years.13 Obesity and weight gain are positively associated with SDB.14 Thus, SDB may become more prevalent than has been previously reported in Japanese. The primary goal of this paper was to examine the prevalence of home-monitored SDB and OSAS in a Japanese working population. The secondary goal was to test the hypotheses that home monitoring with a type 3 portable monitor and actigraphy can produce reliable data to analyze SDB in usual lifestyles. Here, we report the first epidemiologic study in Japan with a type 3 portable monitor and actigraphy at home to examine the prevalence and related factors of SDB.

The present study investigated whether room temperature (T(a)) cycles around dusk and dawn could influence the circadian rhythm of rectal temperature (T(core)), urinary 6-hydroxymelatonin sulfate during nocturnal sleep, and subjective assessments of sleep in humans. Six female and two male students served as participants. Two different T(a) conditions, cyclic and constant, were established. Two kinds of room temperature were provided to subjects: cyclic T(a) (gradual decrease from 27 degrees C to 24 degrees C between 1800 and 2200 h and gradual increase from 24 degrees C to 27 degrees C between 0300 and 0700 h) and constant T(a) (27 degrees C over 24 h). At cyclic T(a), the circadian nadir of T(core) rhythm was significantly advanced, while T(core) was significantly lower from 2300 to 0200 h and significantly higher from 0600 to 1000 h. The nocturnal concentration of 6-hydroxymelatonin sulfate in the urine during sleep was significantly higher during cyclic T(a). Waking sensation just after rising was significantly better with cyclic T(a). (Skin temperatures in the extremities-T(a)) were significantly higher with cyclic T(a) especially during the evening and night. Our results suggest that gradual change of room temperature in the evening and early morning is important in terms of sleep promotion and fresh awakening. It seems probable that mankind has been evolved to have deeper sleep under the influence of cyclic T(a) around dusk and dawn.

SAS患者は日中の眠気や倦怠感などの疾患に起因する症状を紛らわすために睡眠にとって悪い習慣を取ってしまっている可能性が指摘されている。しかしSAS患者の生活実態は明らかになっていない。そこで本研究はSAS患者の生活習慣の実態を明らかにし、Apnea Hypopnea Index (AHI)、Epworth Sleepiness Scale (ESS)、Pittsburgh Sleep Quality Index (PSQI)、Body Mass Index(BMI)との関連を検討することを目的として行った。方法は質問紙およびAHIのデータをカルテより転載し、分析を行った。対象者は睡眠時無呼吸症候群と診断され治療前の方、56名を対象として行い、回収率は86%であった。AHI、ESS、PSQI、BMIと喫煙、飲酒、カフェインの摂取、睡眠時間などとの関連をみたところ、飲酒とBMIとの間に有意な関連がみられた。また喫煙とPSQIに有意な関連がみられ、睡眠の質が低いと評価している人ほど喫煙本数が多かった。睡眠時間とESSおよび希望睡眠時間と睡眠時間の差とESSの間に相関がみられ、SASによる睡眠障害だけでなく、睡眠時間の不足も問題である可能性があると考えられた。ベッドパートナーの有無が睡眠を阻害する因子になりうる可能性が示唆された。今回の対象者では治療開始前であったが、SASの治療の第一選択であるCPAP療法には家族のサポートも重要である。そのため今後ベッドパートナーの有無がCPAP療法にどのような影響を及ぼすのかについても検討していくことが重要であると考える。, It has been pointed out that Sleep Apnea Syndrome (SAS) patients may have adopted life-styles which are poor for their sleep in order to alleviate symptoms that originate in disorders such as sleepiness and fatigue during the day. However, there is no clear evidence of what kind of maladaptive life-styles have been adopted by SAS patients. This research was therefore conducted with the aim of revealing the life-styles of SAS patients, and exploring the relationships between those life-styles and their correlation with the Apnea Hypopnea Index (AHI) data, the Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI) and the Body Mass Index (BMI). It was conducted on 56 pre-treated patients diagnosed with SAS via analysis of questionnaires and AHI data from their medical records. The response-rate was 86%. An analysis of the relationships between the data derived from AHI, ESS, PSQI, and BMI to smoking, alcohol consumption, caffeine intake and sleeping hours showed a significant relationship between alcohol consumption and BMI data. Furthermore, a significant relationship was evident between smoking and PSQI data, with those who evaluated their sleep quality as poor smoking the most. A correlation could also be seen between sleeping time and the ESS data, and the difference between desired hours of sleep and actual sleeping time and the ESS data, indicating that not only sleep disturbance was caused by SAS, but also the lack of sleep time could be a problem. In addition, it was also suggested that the existence of a bed partner could be one factor disturbing sleep. While the subjects of this research had not yet been treated, family support is important to CPAP treatment. For this reason, it will also be essential to study the effect of a bed partner on CPAP treatment in the future.

Short-term compliance of nasal continuous airway pressure (nCPAP) therapy in elderly patients (65 years or older; n = 115) with moderate to severe obstructive sleep apnea was investigated. When nCPAP therapy was offered to elderly patients with an apnea-hypopnea index greater than 20/h, the acceptance rate of nCPAP therapy was 70%. Of those, the short-term tolerance rate of nCPAP therapy (usage over 3 months after initial trial) was 83%. The patients who refused or abandoned nCPAP therapy were less severe (in terms of the apnea-hypopnea index), less sleepy and there were a lower number with hypertension. Considering the short-term compliance of nCPAP therapy reported for middle-aged patients in the literature, it is found that acceptance and short-term tolerance of nCPAP therapy in elderly patients is high, especially in patients with hypertension and excessive daytime sleepiness.

1. The present study is aimed at knowing whether ambient temperature ( T a ) cycles exert any influence on circadian rhythm of rectal temperature ( T re ) in humans. 2. Three different T a conditions were provided: (1) T a was kept constant at 25°C for 24 h (Constant). (2) T a decreased from 25°C to 22°C over 4 h from 1800 to 2200 h, was then kept constant at 22°C for additional 6 h and increased to 25°C over 4 h from 0400 to 0800 h (FLR). (3) T a was changed reversibly from 25°C through 28°C to 25°C with identical time schedule like FLR (RHF). 3. Minimum level and evening decreasing rate/morning increasing rate in T re were significantly the lowest and greatest in FLR.

Background The purpose of the present study is to investigate effects of tryptophan intake and light exposure on melatonin secretion and sleep by modifying tryptophan ingestion at breakfast and light exposure during the daytime, and measuring sleep quality (by using actigraphy and the OSA sleep inventory) and melatonin secretion at night. Methods Thirty three male University students (mean ± SD age: 22 ± 3.1 years) completed the experiments lasting 5 days and 4 nights. The subjects were randomly divided into four groups: Poor*Dim (n = 10), meaning a tryptophan-poor breakfast (55 mg/meal) in the morning and dim light environment (5,000 lx); and Rich*Bright (n = 7), tryptophan-rich breakfast and bright light. Results Saliva melatonin concentrations on the fourth day were significantly lower than on the first day in the Poor*Dim group, whereas they were higher on the fourth day in the Rich*Bright group. Creatinine-adjusted melatonin in urine showed the same direction as saliva melatonin concentrations. These results indicate that the combination of a tryptophan-rich breakfast and bright light exposure during the daytime could promote melatonin secretion at night; further, the observations that the Rich*Bright group had higher melatonin concentrations than the Rich*Dim group, despite no significant differences being observed between the Poor*Dim and Rich*Dim groups nor the Poor*Bright and Rich*Bright groups, suggest that bright light exposure in the daytime is an important contributor to raised melatonin levels in the evening. Conclusions This study is the first to report the quantitative effects of changed tryptophan intake at breakfast combined with daytime light exposure on melatonin secretion and sleep quality. Evening saliva melatonin secretion changed significantly and indicated that a tryptophan-rich breakfast and bright light exposure during the daytime promoted melatonin secretion at this time.

Shift work is the popular working pattern in many fields in industrialized nations. However, the shift workerdoes not pay much attention to his (her) own health. It is known that shift work has strong associations withvarious diseases. The aim of this study was to investigate the relationship between food intake and chronotype inJapanese nurses working an irregular rotation of shifts. This questionnaire-based study used a cross-sectionaldesign. Participants were nurses working in several hospitals, data from 159 respondents being analyzed. Thequestionnaire covered demographics, the Diurnal Type Scale (DTS) and a Food Intake Questionnaire (FIQ). TheDTS scores were classified into three chronotype groups: modified Morning-type (M-type), modifiedEvening-type (E-type) and modified Intermediate-type (I-type). For food intake behavior, meal habits of theM-types were compared with the E-types before / after day- and night-work. In the morning, just after thenight-shift, the M-types chose cold food more frequently (p = .016) and felt less satiated after the meal (p = .016)than the E-types. Furthermore, the E-types chose significantly larger meals (p = .023) than the M-types, theM-types snacking more frequently. Chronotype was associated with the food intake behavior both in day- andnight-shift. These results suggest that the Morning-type person suffered more inconvenience with regard to foodintake behavior during night-work.

This study explores whether morning-typed persons are aware that they are maladapted for shift-work. An integrated questionnaire was administrated to 637 students aged 18-35 yrs attending university or physical therapy training school in May, June and October, 2012. A total of 617 participants (97%) answered the questionnaire that included questions on sleep habits such as bedtime, the diurnal type scale by Torsvall and Akerstedt (1980), questions on mental health (irritation, anger, feeling out of control, depression) and meals content and timing, and questions on experience with and attitude towards shift work, including the question, “Would you be able to mentally and physically withstand doing shift work for one year, if given the chance?” Participants that answered “Absolutely never” to this question (DIFFICULT Group) showed significantly higher scores on the diurnal-type scale (more morning-typed) (p=0.005) and subjectively evaluated themselves as “more morning-typed persons” (p

The purpose of the present study was to investigate how bright light during the daytime could influence circadian rhythms of core temperature and nocturnal sleep. Seven females (age 20 ± 2 years) served as participants. The participants lived in the experimental unit for 4 days and were exposed to either 6000 lx (bright) or 200 lx (dim) light during the daytime. Rectal temperature (T re ) was measured during the experimental period. Subjective alertness was measured by the Kansei-gakuin Sleeping Scale five times a day. The minimum T re was significantly lower after bright exposure (P < 0.05). The T re fell rapidly after bright exposure before they retired (P < 0.05) and increased more rapidly during bright light after they woke up (P < 0.05). The morning wakefulness under bright exposure was more active than under dim exposure (P < 0.05). The melatonin secretion at wake up during bright exposure was significantly lower than during dim exposure (P < 0.05). Exposure to bright light during daytime lowered the nocturnal level of T re , its evening fall was faster and the morning rise quicker. This suggests that indoor light during daytime should be bright enough to promote healthy sleep at night.