Purpose

Observational studies suggest that menopausal hormone therapy protects against sleep-disordered breathing, but such findings may be biased by a "healthy user effect." When the Women's Health Initiative Study reported in 2002 that estrogen-progestin therapy increases heart disease risk, many women discontinued hormone therapy. We investigate healthy user bias in the association of hormone therapy with sleep-disordered breathing in the Sleep in Midlife Women Study.

Methods

A total of 228 women aged 38 to 62 years were recruited from the Wisconsin Sleep Cohort Study. They underwent polysomnography to measure apnea-hypopnea index, at home semiannually from 1997 to 2006, and in the sleep laboratory every four years (n = 1828 studies). Hormone therapy was recorded monthly. Linear models with empirical standard errors regressed logarithm of apnea-hypopnea index on hormone use with a pre- or post-July 2002 interaction, adjusting for menopause and age.

Results

The association of hormone therapy and sleep-disordered breathing was heterogeneous (P < .01); apnea-hypopnea index among users was 15% lower in the early period (95% confidence interval, -27% to -1%), but similar to nonusers in the late.

Conclusions

Hormone therapy was negatively associated with sleep-disordered breathing only until the Women's Health Initiative results were publicized. Hormone therapy may have been a marker for healthfulness in the early period, creating a spurious association with sleep-disordered breathing.

Objective

Menopause is widely believed to be an established cause of sleep disorders, but evidence for this theory is inconclusive. Attributing any sleep problem to normal processes of menopause may lead to underdiagnosis of treatable sleep disorders in midlife women. This study uses detailed longitudinal data on sleep and menopausal health from participants in the Sleep in Midlife Women Study to investigate whether risk and severity of sleep-disordered breathing increase with progression through menopause, accounting for changes in age and body habitus.

Methods

A total of 219 women aged 38 to 62 years were recruited from participants in the Wisconsin Sleep Cohort Study. Menopause status was determined from daily diaries in which participants reported menstrual flow, hot flashes, and use of hormonal medications. Each participant underwent in-home polysomnography studies every 6 months, to measure the apnea-hypopnea index (AHI) (N = 1,667 studies). Linear models with empirical standard errors were fit for logarithm of AHI on menopause status and years in menopause, adjusting for age, body mass index, waist girth, and neck girth.

Results

Compared with women in premenopause, AHI was 21% higher among participants in perimenopause (95% CI, -4 to 54), 31% higher among participants in postmenopause (95% CI, 2-68), and 41% higher among participants whose menopausal stage could not be distinguished between peri- and postmenopause (95% CI, 8-82). Among women who had begun perimenopause, each additional year in menopause was associated with 4% greater AHI (95% CI, 2-6).

Conclusions

Progression through menopause is associated with greater sleep-disordered breathing severity. This association is independent of aging and changes in body habitus.