The effects of sleep duration on the incidence of cardiovascular events among middle-aged male workers in Japan

• Main Authors: Yuko Hamazaki, Yuko Morikawa, Koshi Nakamura, Masaru Sakurai, Katsuyuki Miura, Masao Ishizaki, Teruhiko Kido, Yuchi Naruse, Yasushi Suwazono, Hideaki Nakagawa
• Format: Article
• Language: English
• Published: Nordic Association of Occupational Safety and Health (NOROSH) 2011-09-01
• Series: Scandinavian Journal of Work, Environment & Health
• Subjects: stroke; cardiovascular risk factor; sleep duration; cardiovascular event; cardiovascular disease; follow-up study; worker; sleep; japan; coronary heart disease
• Online Access: https://www.sjweh.fi/show_abstract.php?abstract_id=3168

OBJECTIVES: Although previous epidemiological studies have investigated the relationship between sleep duration and various cardiovascular events, the results have been inconsistent. Accordingly, we conducted a follow-up survey to investigate the relationship between sleep duration and cardiovascular events among male workers, accounting for occupational factors that might confound the true relationship. METHODS: A total of 2282 male employees aged 35–54 years based in a factory in Japan were followed for 14 years. The risk of cardiovascular events was compared among 4 groups stratified based on sleep duration at baseline (<6, 6–6.9, 7–7.9, and ≥8 hours). Cardiovascular events included stroke, coronary events and sudden cardiac death. The hazard ratios for events were calculated using a Cox proportional hazards model, with the 7–7.9-hour group serving as a reference. The model was adjusted for potential confounders including traditional cardiovascular risk factors and working characteristics. RESULTS: During 14 years of follow-up, 64 cardiovascular events were recorded including 30 strokes, 27 coronary events and 7 sudden cardiac deaths. After adjustment for possible confounders, the hazard ratios for cardiovascular and coronary events in the <6-hour group were 3.49 [95% confidence interval (95% CI) 1.30–9.40] and 4.95 (95% CI 1.31–18.73), respectively. There was no significant increment in the risk of stroke for any sleep duration groups. CONCLUSION: Short sleep duration (<6 hours) was a significant risk factor for coronary events in a Japanese male working population.