Sleep disturbance during the menopausal transition in a multi-ethnic community sample of women.

TWO RELATIVELY CONSISTENT FINDINGS HAVE EMERGED FROM EPIDEMIOLOGIC STUDIES OF SLEEP DISTURBANCES: THAT SUBJECTIVE REPORTS OF difficulty sleeping are more prevalent in women than men and that the prevalence of this difficulty increases with aging.1,2 A female preponderance in the prevalence of self-reported sleep problems is evident by midlife.3–7 Data presented at the NIH State-of-the-Science Conference on Management of Menopause-Related Symptoms8 indicated that sleep problems are reported by 16%-42% of premenopausal women, 39%-47% of perimenopausal women, and 35%-60% of postmenopausal women. In the Study of Women's Health Across the Nation (SWAN) cross-sectional survey of more than sixteen thousand women aged 40–55 years, 38% experienced difficulty sleeping within the 2 weeks preceding the interview.9 Relative to being premenopausal, being perimenopausal was associated with difficulty sleeping even after adjusting for multiple relevant covariates. Both age and hormonal changes can contribute to disturbed sleep in middle-aged women undergoing the menopausal transition.10–14 Whereas the increase in sleep difficulties that emerge at midlife suggest an aging effect,10,11,14 gender differences at midlife suggest that the role of aging per se must be distinguished from sleep disturbances due to other age-related risk factors.13 In the initial SWAN report,9 we may have found no “age effect” because we only included women in a narrow age range during a period of marked hormonal transition when ovarian age may be more informative than chronological age. Attributes of the menopausal transition may confer risk for sleep disturbances beyond the effects of age alone, but studies examining these factors have tended to be cross-sectional. Potential precipitating factors during the menopausal transition include onset and exacerbation of vasomotor symptoms (VMS; hot flashes, night sweats, cold sweats)15 and changing reproductive hormone levels (especially follicle stimulating hormone; FSH).16 The etiology of perimenopausal-related sleep changes and whether onset of these changes is associated with hormonal changes and VMS that occur during this transition are not well understood.17,18 VMS are highly prevalent in peri- and postmenopausal women (35%-80%),8,19 and there is considerable overlap between VMS and sleep difficulties.20 Whereas sleep disturbance and VMS are strongly associated, these 2 symptoms are not perfectly correlated, and sleep difficulties may continue long after hot flashes have subsided.21 Menopausal hormonal changes may plausibly be related to acute sleep disturbances, but evidence relating self-reported sleep difficulties to hormonal changes, independent of VMS, during the menopausal transition has been mixed.22 In SWAN,16 FSH concentrations, but not FSH-adjusted estradiol levels, are strongly related to VMS. Others have shown that in women aged 35–49 years, poor sleep quality is associated with lower follicular phase plasma estradiol.23 Data from SWAN's Daily Hormone Study (daily collection of first morning urine for up to 50 days and self-reported sleep difficulties) showed that compared with premenopausal women, early perimenopausal women had 29% higher odds of reporting trouble sleeping.12 This increased reporting was associated with levels of the urinary progesterone metabolite, pregnanediol glucuronide, in perimenopausal women and with FSH levels in premenopausal women, independent of VMS.12 An additional, though largely unexplored issue, is the type of sleep difficulty most prevalent during the menopausal transition. An examination of sleep problems over 12 months in the National Comorbidity Survey Replication, a nationally representative household survey of men and women 18 years and older, showed little variation in types of reported problems: 16.4% had difficulty initiating sleep, 19.9% had difficulty maintaining sleep, and 16.7% had early morning awakenings.24 However, these cross-sectional data were not reported by age or sex. Little is known about the prevalence of these 3 types of disturbed sleep during and after the menopausal transition and how they vary over long periods of time. We undertook a longitudinal analysis of data from an ethnically diverse cohort of midlife women to determine how each type of sleep continuity difficulty changes as they progressed through the menopausal transition. Specifically, we examined whether three aspects of the menopausal transition, i.e., changes in bleeding patterns, reproductive hormone levels, and VMS, affected sleep symptom reports after accounting for the effects of aging and a variety of health and psychosocial factors. We also examined whether the associations varied among the 5 racial/ethnic groups represented in SWAN.