Hot flashes and sleep disruption in a randomized trial in menopausal women.

Background: Hot flashes, common during menopause, affect up to 80% of the Western menopausal women and are reported to contribute to sleep disturbances in midlife. Few prospective data are available to confirm the specific role of hot flashes in disrupting sleep in midlife women, however, or confirm whether changes in hot flashes in response to clinical therapies result in improvement in sleep.

Objective: To examine the effects of continuous nitroglycerin therapy on sleep quality in perimenopausal and postmenopausal women with frequent hot flashes (pre-specified secondary trial endpoint) and to examine prospective associations between hot flashes and sleep disruption in this population.

Study design: Sleep data were analyzed from a randomized, double-blinded, placebo-controlled trial of continuous transdermal nitroglycerin (NTG) therapy to suppress nitric oxide-mediated vasodilation in perimenopausal or postmenopausal women with hot flashes. Participants were randomized to uninterrupted use of transdermal NTG (0.2-0.6 mg/hour) or placebo for 12 weeks. Nocturnal hot flashes awakening participants from sleep were evaluated using 7-day symptom diaries at baseline, 5 weeks, and 12 weeks. Sleep disruption (wakefulness after sleep onset, WASO) was assessed using validated sleep diaries, and global sleep quality was assessed by the validated Pittsburgh Sleep Quality Index (PSQI: range 0 [best] 21 [worst]) questionnaire. Mixed linear models examined changes in sleep quality and disruption, as well as the strength of associations between nocturnal hot flash frequency and sleep outcomes, over 5 and 12 weeks, adjusting for baseline values, age, race, and ethnicity.

Results: Among the 141 participants (70 to NTG and 71 to placebo, mean age 54.6 [±3.9] years), the mean baseline hot flash frequency was 10.8 (±3.5) per day, including 2.6 (±1.7) nocturnal hot flashes awakening participants. At baseline, hot flashes were the most commonly reported reason for nocturnal awakening, with 62.6% of participants reporting waking due to hot flashes at least twice nightly. Over 5 and 12 weeks, mean frequency of nocturnal hot flashes causing awakenings decreased in both groups (NTG: -0.9 episodes/night, placebo: -1.0 episodes/night). Sleep disruption as measured by average nightly WASO also decreased (NTG: -10.1 minutes, placebo: -7.3 minutes), and mean PSQI score improved (NTG: -1.3 points, placebo: -1.2 points). No significant between-group differences in change in sleep outcomes were detected from baseline to 5 and 12 weeks, including PSQI sleep quality score as a prespecified secondary trial endpoint (P≥.05 for all). Greater improvement in nocturnal hot flash frequency over 5 and 12 weeks was associated with greater improvement in PSQI sleep quality score (β= -0.30, P=.01) and sleep disruption reflected by WASO (β= -1.88, P=.02) in the combined sample.

Conclusion: Among menopausal women in a randomized trial of continuous NTG therapy for hot flashes, hot flashes were the most frequently reported cause of nocturnal awakenings. Compared to placebo, continuous NTG therapy did not result in greater improvements in sleep quality from baseline to 5 and 12 weeks. Based on night-by-night symptom diaries and questionnaires, however, greater improvement in nocturnal hot flash frequency in both groups was associated with greater improvement in sleep quality and disruption.