Sleep duration and the onset of menopause in Japanese women.

OBJECTIVE: Sleep characteristics may potentially affect the hormonal environment related to follicular degeneration. The present study aimed to examine the association between sleep duration and the onset of menopause in Japanese women.

METHODS: We conducted a prospective study among 3,090 premenopausal Japanese women aged 35 to 56 years derived from participants in the Takayama Study. Habitual sleep duration was determined by a self-administered questionnaire at the baseline. Menopausal status was defined as the absence of menstruation for 12 months or more. The Cox proportional hazard model was used to estimate the hazard ratio of the occurrence of menopause for each category of sleep duration (≤6, 8, and ≥9 h) as compared with 7 hours of sleep after controlling for age, parity, body mass index, smoking status, years of education, and lifelong irregular menstrual cycle.

RESULTS: During the 10 follow-up years, 1,776 women experienced natural menopause. Sleep duration of ≤6 hours was significantly associated with decreased hazard ratio of menopause (0.88; 95% confidence interval, 0.78-0.99).

CONCLUSIONS: The data suggest that short sleep duration is associated with later onset of menopause.