Tomoko Wakamura

Differences in relationships among sleep apnoea, glucose level, sleep duration and sleepiness between persons with and without type 2 diabetes

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 ± 8 years; body mass index, 23.9 ± 3.1 kg 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 7 days, 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 ± 3.8 kg m−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.

Association Between Sleep Apnea, Sleep Duration, and Serum Lipid Profile in an Urban, Male, Working Population in Japan

BACKGROUND 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. METHODS 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. RESULTS According to Japanese criteria, 143 subjects had dyslipidemia. Percent sleep time of oxygen saturation as measured by pulse oximetry (SpO2) < 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, P < .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, P < .01), and alcohol intake (β = 0.20, P < .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). CONCLUSIONS 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.

Effects of the presence of hypertension on the relationship between obstructive sleep apnoea and sleepiness

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.

Associations among Chronic Obstructive Pulmonary Disease and Sleep-Disordered Breathing in an Urban Male Working Population in Japan

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.

Impact of sleep characteristics and obesity on diabetes and hypertension across genders and menopausal status: the Nagahama study

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.

Association between socioeconomic factors and urinary sodium-to-potassium ratio: the Nagahama Study

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 < 0.001), whereas no significant association was observed with household income. Men, particularly individuals living alone, exhibited markedly high sodium-to-potassium ratios (3.6 ± 2.3). Although frequent intake of vegetables, fruits, and dairy products was also inversely associated with the ratio, the associations with educational attainment ( ≤ 9: reference, ≤ 12: β = −0.032, P = 0.026, ≥ 13: β = −0.059, P < 0.001), marital status (β = −0.040, P < 0.001), and sex*marital status interaction (β = 0.054, P = 0.001) were independent of these covariates. Educational attainment was also inversely associated with differences in the urinary sodium-to-potassium ratio during the follow-up period (odds ratio, 0.70; P < 0.001). Lower educational attainment was an independent determinant for urinary sodium-to-potassium ratio. Health literacy education, particularly in men living alone, may be a factor for reducing salt intake even in high-income countries where equal educational opportunity is assured.

Seasonal variation in nocturnal home blood pressure fall: the Nagahama study

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 < 0.001), resulting in higher frequencies of riser (summer, 19.9; middle, 12.8; winter, 7.8%) and non-dipper (summer, 51.4; middle, 46.3; winter, 37.0%) patterns in the summer season (p < 0.001). The results of linear regression analysis identified the middle (β = 0.154, p < 0.001) and summer season (β = 0.261, p < 0.001) as strong positive determinants for decreasing the nocturnal SBP fall. No seasonality was observed in day-to-day variability of the dipping pattern (Kendall’s coefficient: winter, 0.527; middle, 0.539; summer, 0.515). The nocturnal BP fall was largely different by season, with a higher frequency of riser and non-dipper patterns in the summer. The seasonality might not be due to the seasonal difference in day-to-day variability of nocturnal BP changes.

Bright-light exposure during daytime sleeping affects nocturnal melatonin secretion after simulated night work

ABSTRACT 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.

Day-to-Day Home Blood Pressure Variability and Orthostatic Hypotension: The Nagahama Study

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.