The influence of habitual physical activity and sedentary behavior on objective and subjective hot flashes at midlife.

Objective: The purpose of this study was to evaluate relationships between physical activity, sedentary time, and hot flashes during both waking and sleeping periods using concurrent objective and subjective measures of hot flashes in midlife women.

Methods: Women aged 45 to 55 years (n = 196) provided self-reported data on physical activity and underwent 24 hours of hot flash monitoring using sternal skin conductance. Participants used event marking and logs to indicate when hot flashes were perceived. Wake and sleep periods were defined by actigraphy. Mean ambient temperature and humidity were recorded during the study period. Generalized linear regression modeling was used to evaluate the effect of physical activity types and sedentary time on hot flash outcomes. Isotemporal substitution modeling was used to study the effect of replacing sedentary time with activity variables on hot flash frequency.

Results: Modeled results indicated that increasing sitting by 1 hour was associated with a 7% increase in the rate of objectively measured but not subjectively reported hot flashes during sleep. Replacing 1 hour of sitting with 1 hour of vigorous activity was associated with a 100% increase in subjectively reported but not objectively measured waking hot flashes. There was little evidence for an effect of temperature or humidity on any hot flash outcome.

Conclusions: These data provide support for relations between sedentary time, physical activity, and hot flashes and highlight the importance of using objective and subjective assessments to better understand the 24-hour hot flash experience.