Monitoring of the sleep patterns of shift workers in the automotive industry.

OBJECTIVE: The effect of shift schedules on the amount of sleep that workers receive is an important factor in workplace health and safety as well as the employees' overall quality of life. The objective of this study is to compare sleep period among workers engaging in each of the three-shift work. METHODS AND PARTICIPANTS: The amount of sleep (sleep period) that male workers with rotating shift schedules received was measured using accelerometers. The mean age of the 16 male workers enrolled in this study was 54.3 years (one standard deviation, 6.7 years). Thirteen participants ranged in age from 51 to 60 years of age, and the other three participants were 32, 48, and 50 years old. Work shifts were rotated on a weekly basis and were categorized into three periods: shift-1 (8:00 to 17:00), shift-2 (15:00 to 23:50), and shift-3 (23:30 to 8:15). Each work week consisted of 5 days. RESULTS: No significant differences were observed in the mean sleep period for each of the three shifts. However, the sleep periods during shift-1 or shift-2 tended to be longer than that obtained during shift-3. No effect of age on the length of the sleep period was observed. CONCLUSIONS: Rotating shift-work did not affect the amount of sleep that workers obtained. However, a comparison with previous study results suggests that morning shifts (starting at 6 AM) and day shifts (starting at 8 AM) may have different effects on sleep time.

Anthropometric obesity indices and metabolic syndrome in Japanese working men.

BACKGROUND: Although the prevalence of obesity in the Japanese adult population is lower than that in the US adult population, there appears to be a trend towards increase in the prevalence of obesity in Japanese men. In this study, the usefulness of waist circumference (WC) and body mass index (BMI) determination as predictors of metabolic syndrome (MetS) was evaluated in Japanese working men. METHODS: A cross-sectional study was conducted in the spring of 2007. The sample included 3,486 working men aged 35 to 59 years. The standard criteria of the International Diabetes Federation were used to determine the prevalence of MetS. The results were adjusted for age, smoking, habitual drinking and serum uric acid. To calculate the OR, MetS was tentatively defined as the presence of two or more of the following criteria in the subjects: high blood pressure, glucose intolerance, and dyslipidemia. RESULTS: The prevalence of MetS was 17.0%, and it increased with age until the mid-50s. The percentages of subjects with high blood pressure, glucose intolerance, dyslipidemia and hyperuricemia were 57.3, 12.7, 29.4 and 21.3%, respectively. As compared to that in the subjects classified in the lowest WC quintile, the ORs (95% confidence interval (CI)) for MetS of a WC in the range of 76.0 to 81.4, 81.5 to 85.9, 86.0 to 90.9, and >or= 91 cm were 1.66 (1.13-2.45), 1.74 (1.13-2.67), 2.37 (1.50-3.74), and 2.84(1.73-4.64), respectively. In contrast, the OR (95% CI) for MetS of a BMI in the range of 24.5 to 26.5 and >or= 26.6 Kg/m2 were 2.43 (1.58-3.73) and 3.27 (2.04-5.27), which just about reached the significance level. CONCLUSIONS: The risk of MetS was correlated with the obesity indices. However, BMI values in the high normal range were not significantly associated with the risk of MetS.

Activity and sleeping time monitored by an accelerometer in rotating shift workers.

BACKGROUND: The relationship between total sleep time and activity levels during work before or after sleep in two rotating work shifts was compared. METHOD: Monitoring of activity levels using an activity-detecting device in the wrist was conducted in 17 rotating shift workers, who ranged in age from 34 to 55 years. The work shifts, consisting of a morning shift (6:30 to 15:15 hours) and an evening shift (15:15 to 24:00 hours), were rotated on a weekly basis. Partial correlation coefficient was calculated after controlling for age. RESULTS: The total sleep time after the morning shift was significantly related to the activity count before sleep (r=-0.42) or after sleep (r=-0.36). There was also a significant relationship between total sleep time after the evening shift and the activity count before sleep (r=-0.39) or after sleep (r=-0.32). The mean total sleep time of the subjects for the morning shift was 349 minutes, which was significantly lower than that after the evening shift (382 minutes). In addition, the activity count during the morning shift was significantly higher than that during the evening shift. CONCLUSIONS: The negative relationship between sleep time and activity before or after sleep became clear in shift workers.