Clearly, additional research to elucidate hot flash physiology is needed. Validated markers of neurotransmission activity in the brain would be nice to have.
Hot Flash Measurement
Another article in this issue of Menopause by Otte et al (9) describes a physiologic measure of hot flashes, involving sternal skin conductance. Women who have hot flashes, and thus sweat, have an increased conductance across two attached skin electrodes. In a controlled trial laboratory setting, there is a very high correlation between hot flashes detected by this sternal conductance monitor and by participant reports of hot flashes.10 In real-life situations, however, correlations between hot flashes measured by daily diaries and those measured by event monitoring devices do not correlate quite as well with sternal conductance monitor
Given this, it has been proposed that sternal skin conductance represents a new criterion standard and should be used in clinical trials to measure hot flashes and, therefore, the efficacy for agents improving hot flashes.12
Nonetheless, we propose that physiologic measures of hot flashes are not ripe enough to replace the time-honored standard of prospective participant hot flash diaries. There are several factors that support this contention. First, hot flash diaries have been validated,13 and a recent meta-analysis demonstrated
remarkably consistent data across studies that used hot flash diaries.3 Second, these physiologic measures of hot flashes actually measure sweating, which can result from sympathetic activation. However, there are other etiologies for sympathetic activation resulting in sweating as well as other causes of sweating other than hot flashes. If an individual sweats from climbing a couple flights of stairs, or other physical activity, this could be judged to be a hot flash when, in fact, it is not. Related to this issue, one of the investigators working with us, to check to see whether a monitor will record a sweating episode, put the device on
herself and walked up a couple flights of stairs.