OBJECTIVE: The impact of hot flashes on sleep is of great clinical interest, but results are inconsistent, especially when both hot flashes and sleep are measured objectively. Using objective and subjective measurements, we examined the impact of hot flashes on sleep by inducing hot flashes with a gonadotropin-releasing hormone agonist.

METHODS: The gonadotropin-releasing hormone agonist leuprolide was administered to 20 healthy premenopausal volunteers without hot flashes or sleep disturbances. Induced hot flashes were assessed objectively (skin conductance monitor) and subjectively (daily diary) during 1-month follow-up. Changes from baseline in objective sleep quality (actigraphy) and subjective sleep quality (Pittsburgh Sleep Quality Index) were compared between women who developed and women who did not develop objective hot flashes and, in parallel analyses, subjective hot flashes.

RESULTS: New-onset hot flashes were recorded in 14 (70%) women and reported by 14 (70%) women (80% concordance). Estradiol was universally suppressed. Objective sleep efficiency worsened in women with objective hot flashes and improved in women without objective hot flashes (median decrease, 2.6%; median increase, 4.2%; P = 0.005). Subjective sleep quality worsened more in those with subjective hot flashes than in those without subjective hot flashes (median increase in Pittsburgh Sleep Quality Index, 2.5 vs 1.0; P = 0.03). Objective hot flashes were not associated with subjective sleep quality, nor were subjective symptoms linked to objective sleep measures.

CONCLUSIONS: This experimental model of induced hot flashes demonstrates a causal relationship between hot flashes and poor sleep quality. Objective hot flashes result in worse objective sleep efficiency, whereas subjective hot flashes worsen perceived sleep quality.