Is sternal skin conductance monitoring a valid measure of hot flash intensity or distress?

OBJECTIVE: To examine the validity of using sternal skin conductance monitoring as a measure of hot flash intensity and hot flash distress.
DESIGN: Descriptive, prospective, longitudinal data from the 2-week baseline of a larger hot flash intervention study; 73 breast cancer survivors with daily hot flashes wore a hot flash monitor and completed a hot flash diary during two 24-hour assessment periods that were separated in time by 1 week.
RESULTS: Data consisted of 569 diary rated hot flashes; 46.9% had magnitude of less than 2.0 micromhos (insufficient to meet objective hot flash criterion) and 26.3% had magnitude of 0.0 micromho (no change in skin conductance). Results from mixed-linear modeling indicated that, although magnitude significantly predicted hot flash intensity and distress, effect sizes were very small: less than 2% when using all observations, and less than 1% when using only the subset meeting objective hot flash criteria. Even after adjusting for covariates that were associated with intensity or distress, magnitude explained very little variance in intensity or distress (<2.2%). Scatterplots and locally weighted smooth regression curves also revealed very little relationship between magnitude and either intensity or distress.
CONCLUSIONS: Findings indicate that objective change in sternal skin conductance, an indicator of sweat gland activity, should not be used as a proxy measure of subjective hot flash intensity or distress. Future research should continue to subjectively measure hot flash intensity and distress when these are important outcome variables to consider.