Type of Menopause, Age at Menopause, and Risk of Developing Obstructive Sleep Apnea in Postmenopausal Women.

Despite established sex differences and longstanding hypotheses of sex hormone influence in the etiology of obstructive sleep apnea (OSA), we have found no studies that evaluated type of menopause and age at menopause, which affect postmenopausal hormonal milieu, in relation to OSA risk in women. We followed 50,473 postmenopausal women from the Nurses' Health Study during 2002-2012 and 53,827 postmenopausal women from the Nurses' Health Study II during 1995-2013, with 1,712 and 2,560 incident OSA diagnoses, respectively. Compared with natural menopause, the pooled hazard ratio for OSA was 1.27 (95% confidence interval (CI): 1.17, 1.38) for surgical menopause by hysterectomy/oophorectomy. The association remained the same after further accounting for age at menopause (hazard ratio = 1.26, 95% CI: 1.15, 1.38). The risk associated with surgical menopause was higher among women who were not obese as well as among women who never used hormone therapy (P for interaction < 0.05). Earlier menopause was associated with higher OSA risk prior to adjustment for type of menopause (comparing those aged <40 years versus those aged 50-54 years, hazard ratio = 1.21, 95% CI: 1.08, 1.35; P for trend = 0.008), although no association was observed after the adjustment. Surgical as compared with natural menopause was independently associated with higher OSA risk in postmenopausal women. Our results provide additional evidence for a role for sex hormones, particularly abrupt hormonal changes, in modulating OSA risk.