Objective: To evaluate the prevalence of different types of nocturnal breathing abnormalities in postmenopausal women and the effect of estrogen replacement therapy (ERT) on nocturnal breathing.
Methods: A prospective, randomized, placebo-controlled, double-blind, crossover study was completed by 62 of 71 recruited healthy women. The first 3-month treatment period with either estrogen or placebo was followed by placebo washout for a month and then by a second treatment period with crossover to either estrogen or placebo. On a night after each treatment period, sleep was monitored with polysomnography, and breathing was assessed with a static-charge-sensitive bed and oximeter. For the respiratory variables, a sample size of 48 subjects was sufficient to give statistical power of 85% with a significance level of P <.05.
Results: The occurrence of obstructive sleep apnea in all women was low (1.6%), but partial upper airway obstruction, manifesting as an increased respiratory resistance pattern, was more common (17.7%). Estrogen replacement therapy decreased the occurrence (P =.047) and frequency (P =.049) of sleep apnea but had no effect on partial upper airway obstruction or arterial oxyhemoglobin saturation.
Conclusion: Partial upper airway obstruction is the most prevalent form of sleep-disordered breathing, occurring ten times more frequently than sleep apnea in postmenopausal women. Unopposed estrogen replacement therapy has only a minor effect on sleep apnea and has no effect on partial airway obstruction.