Estrogen replacement therapy moderates the sleep disruption associated with nocturnal blood sampling

Study Objectives: To determine whether chronic oral estrogen replacement th erapy (ERT) (1) improves the sleep of older, non-symptomatic postmenopausal women; and (2) reduces the sleep disruption associated with a stressor (fr equent remote nocturnal blood-sampling through an intravenous catheter). Design: Descriptive, cross-sectional, secondary analysis of a larger study. Setting: The General Clinical Research Center at the University of Washingt on Medical Center. Participants: Women aged 57-80 (mean age = 70) at least 5 years past menopa use were recruited from the community. Hot flashes and significant sleep di fficulties were exclusion criteria. The ERT group (n=37) consisted of women on chronic oral ERT for greater than or equal to2 years. The NERT group (n =56) consisted of women not using estrogen (NERT) for greater than or equal to2 years. Interventions: N/A Measurements and Results: Following an adaptation night, polysomnographic m easures were collected for 2 consecutive nights. A blood sample was collect ed every 20 minutes for the last 24 hours (including Night 2), through an i ntravenous catheter. The only group difference in sleep on the baseline (no n-catheter) night was that NERT women had a shorter sleep latency. Sleep on the catheter night was characterized by increased wakefulness, longer slee p latency, and decreased REM sleep for both groups relative to the baseline . However, the impact of nocturnal blood sampling was much greater for INER T than for ERT women: they experienced significantly greater percent change s in more sleep-wake variables, particularly slow-wave sleep (SWS). Conclusions: In this cross-sectional study, the use of chronic oral ERT was associated with little effect on the sleep of older postmenopausal women n ot experiencing hot flashes, except in the presence of a challenge to sleep . ERT ameliorated the disruptive effect of nocturnal blood sampling on both objectively assessed and subjectively assessed sleep.