How well do different measurement modalities estimate the number of vasomotor symptoms? Findings from the Study of Women's Health Across the Nation FLASHES Study.

OBJECTIVE: Studies of vasomotor symptoms (VMS) typically measure VMS via daily diaries completed at the end of the day. VMS can also be measured via diaries completed throughout the day or via physiological monitors-modalities with lower recall demands. We examined the degree of correspondence between three VMS measurement modalities: retrospective end-of-day/morning diaries, prospective reporting, and physiological monitoring. We determined whether discrepancies between measurement modalities varied by participant characteristics.
METHODS: Twenty-five African-American women and 27 white women from the Pittsburgh site of the Study of Women's Health Across the Nation who were experiencing VMS, had intact uterus and ovaries, and were free of medications affecting VMS underwent 4 days of ambulatory VMS and Actiwatch monitoring. VMS were recalled in end-of-day and morning diaries, reported prospectively during the day, and measured physiologically via a hot flash monitor. Associations between anxiety, sleep, or race/ethnicity and VMS measurement modality difference scores were examined using generalized estimating equations.
RESULTS: Women underestimated the number of daytime VMS at the end of the day as compared with VMS that were prospectively reported or physiologically measured throughout the day. This pattern was particularly pronounced among African-American women (b [SE] = -3.01 [0.93], P = 0.001) and women with higher anxiety (b [SE] = -3.13 [1.53], P = 0.04). For nighttime VMS, women overestimated the number of VMS in the morning upon waking as compared with prospective measures, particularly if they had poorer sleep (higher wakening after sleep onset: b [SE] = 0.03 [0.008], P = 0.001).
CONCLUSIONS: Different measurement modalities yield different VMS estimates. Negative affect, sleep, and race/ethnicity may affect the recall of VMS.