Study objectives: To compare the prevalence and severity of sleep apnea between premenopausal and postmenopausal women, and to determine whether these differences are affected by the body mass index (BMI) and neck circumference.
Design: Cross-sectional study utilizing a sleep clinic patient database.
Setting: University hospital.
Patients: A total of 1,315 women, classified into premenopausal and postmenopausal groups based on age (< 45 years and > 55 years, respectively).
Measurements: Anthropometric measurements included height, weight, and neck circumference. Sleep measurements included full nocturnal polysomnography. Sleep apnea was defined as an apnea-hypopnea index (AHI) > 10/h.
Results: There were 797 premenopausal and 518 postmenopausal women. The latter group was more obese (mean +/- SE BMI, 32.2 +/- 0.4 kg/m(2) vs 30.2 +/- 0.4 kg/m(2); p < 0.0001) and had larger neck circumference (37.1 +/- 0.2 cm vs 35.8 +/- 0.2 cm; p < 0.0001). The prevalence of sleep apnea was greater in postmenopausal women than premenopausal women (47% vs 21%; chi(2) < 0.0001). There were proportionately more postmenopausal than premenopausal women in all ranges of apnea severity (AHI, 10 to 30/h, 30 to 50/h, and > 50/h). Postmenopausal women had a significantly higher mean AHI compared to premenopausal women (17.0 +/- 0.9/h vs 8.7 +/- 0.6/h; p < 0.0001); this significant difference persisted even after adjusting for BMI and neck circumference.
Conclusion: There may be functional, rather than anatomic, differences in the upper airway between premenopausal and postmenopausal women, which may account for the observed differences in apnea prevalence and severity.