Subjective and objective measures of hot flashes

Abstract

Up to 75% of women in the US report having experienced hot flashes during the menopausal transition. The purpose of this review is to describe the physiology of hot flashes, and the ways in which hot flashes have been examined by subjective report and by objective measurement. Hot flashes occur because of an activation of the heat dissipation response, possibly triggered by a hypothalamic mechanism within the context of declining estrogen levels. There is cross-population variation in the frequency of self-reported hot flashes, although cross-study comparisons are problematic because of incompatibilities in study design. Diaries are a good way to collect information on the time and severity of hot flashes, and body diagrams allow researchers to study the pattern of heat and sweating. Hot flashes can be objectively measured by increases in heart rate, finger blood flow, respiratory exchange ratio, skin temperature, and core body temperature. Sternal skin conductance is the method most highly correlated with subjective hot flash report. In a laboratory, concordance between subjective report and sternal skin conductance can approach 100%. Ambulatory monitoring allows for the tracking of hot flashes during a woman's daily routine or sleep; however, concordance is much lower with ambulatory, compared to laboratory, monitoring. The study of hot flashes at menopause provides a model for the study of any experience that can be assessed by both self-report and biometric measurement.