Relationships Among BMI, Estradiol, And Sleep-wake Behavior In Women

Abstract

PURPOSE: It has been estimated that women are at 40% increased risk for developing clinically significant sleep disturbances (such as insomnia) compared to men. Reproductive-related hormones, such as estradiol (E2), have been shown to play a key role in sleep-wake behavior in women, and pharmacological interventions which target the regulation of E2 have been shown to improve sleep in women. Importantly, body mass index (BMI) has been shown to be inversely associated with E2 levels in premenopausal women, and previous studies have also suggested that women who are overweight or obese are significantly more likely to report clinically-significant sleep disturbances. Thus, this study aimed to examine associations between BMI, E2, and sleep disturbances in premenopausal women in order to identify a non-pharmacological, physical activity (PA) related modifiable target for the prevention of clinically significant sleep problems in women. METHODS: Following a two-tiered screening process, 28 healthy women (18-45y, mean age: 24.6y) who were medication-free and had regular menstrual cycles completed: (1) enrollment visit, (including mood and sleep assessment and assessment of cardiorespiratory fitness via maximal oxygen consumption during exercise); (2) one-week sleep monitoring period (objective and subjective measures of sleep-wake behavior); and (3) saliva collection for the assessment of salivary E2 levels. Saliva collection occurred during the follicular phase of the menstrual cycle to control for ovarian cycle E2 fluctuations. RESULTS: Higher BMI was significantly associated with lower E2 levels (r = -.38, p = 0.04), and also longer objectively-measured sleep onset latency (SOL) duration (r = .51, p = 0.004). Consequently, lower E2 levels were significantly associated with increased objectively-measured wake after sleep onset (WASO) duration (r = -.43, p = 0.03) and increased number of awakenings during the sleep period (r = -.48, p = 0.01). CONCLUSIONS: Results suggest that, in premenopausal women, higher BMI may be associated with increased sleep disturbances, and that this relationship may be mediated by E2 levels. It is therefore possible that regular PA, which has been shown to be inversely associated with BMI, may improve sleep via its positive effects on adiposity and associated regulation of E2.