Objective: Many studies have found a significantly lower frequency of reported hot flashes (HFs) in Japanese and Japanese American (JA) populations, leading to speculation about possible dietary, genetic, or cultural differences. These studies have relied on subjective reports of HFs. Accordingly, the purpose of this study was to compare both reported and objective HFs measured by sternal and nuchal skin conductance among JA and European American (EA) women.
Methods: Two surveys of HF frequencies were carried out among women of either EA or JA ethnicity; aged 45 to 55 years; living in Hilo, Hawaii; and not using exogenous hormones. The first was a postal questionnaire (n = 325); the second was carried out during a clinical study of HFs (n = 134). Women in the second group underwent 24-hour ambulatory and 3-hour laboratory monitoring for objective HFs measured through skin conductance at sternal and nuchal sites. Subjective HFs were recorded on the monitor or in a diary.
Results: JAs were significantly less likely to report having had HFs in the previous 2 weeks compared with EAs (postal sample: JAs, 30.9%; EAs, 43.9%; χ2 = 6.9, P < 0.01; monitored sample: JAs, 26.1%; EAs, 46.6%; χ2 = 5.3, P < 0.05). JAs were also significantly less likely to report experiencing other symptoms (15 of 30 in the postal sample; 6 of 30 in the monitored sample) than EAs. However, JAs did not significantly differ in likelihood of reporting subjective HFs during the 24-hour ambulatory period (JAs, 51.1%; EAs, 55.8%; χ2 = 0.3, NS), nor in percentage of individuals displaying one or more objective HFs as measured by the skin conductance monitor (JAs, 77.8%; EAs, 72.1%; χ2 = 0.5, NS). JAs also did not have a significantly fewer number of objective HFs (t = 0.2, NS) nor of subjective HFs (t = 0.8, NS) during the monitoring period, and these results were unchanged when analyses controlled for menopause status and body mass index.
Conclusions: The common finding of fewer reported HFs in people of Japanese ancestry may be a consequence of reporting bias: JAs report fewer symptoms of many conditions compared with people from other ethnic groups. This is probably due to cultural conceptions of what is appropriate to report.