Geographical distribution of hot flash frequencies: Considering climatic influences

Abstract

Laboratory studies suggest that hot flashes are triggered by small elevations in core body temperature acting within a reduced thermoneutral zone, i.e., the temperature range in which a woman neither shivers nor sweats. In the present study, it was hypothesized that women in different populations develop climate-specific thermoneutral zones, and ultimately, population-specific frequencies of hot flashes at menopause. Correlations were predicted between hot flash frequencies and latitude, elevation, and annual temperatures. Data on hot flash frequencies were drawn from 54 studies. Pearson correlation analyses and simple linear regressions were applied, first using all studies, and second using a subset of studies that included participants only to age 60 (n = 36). Regressions were repeated with all studies, controlling for method of hot flash assessment. When analyses were restricted to studies that included women up to age 60, average temperature of the coldest month was a significant predictor of hot flash frequency (P < 0.01), explaining 29.2% of the variation in hot flash frequency. In a separate equation, the difference between hottest and coldest temperatures was also a significant predictor (P < 0.01), explaining 26.4% of the variation in hot flash frequency. When regressions used all studies but controlled for method of hot flash assessment, average temperature of the coldest month, difference between hottest and coldest temperatures, and mean annual temperature were significant predictors of hot flash frequency. Women reported fewer hot flashes in warmer temperatures, and more hot flashes with increasing seasonality. These results suggest that acclimatization to coldest temperatures or sensitivity to seasonality may explain part of the population variation in hot flash frequency.

A large multinational study of vasomotor symptom prevalence, duration, and impact on quality of life in middle-aged women

“…Women in warmer temperatures report fewer hot flushes, and the difference between the hottest and coldest temperatures was also a significant predictor. 64 Conversely, others have reported a direct relation between warmer climate and more intense hot flushes. 23 A direct relation between hot flushes and the number of cigarettes smoked has been 65 This was not the case in our series, perhaps because of the fact that smoking habit is low among middleaged Latin American women.…”

Prevalence of hot flushes and night sweats around the world: a systematic review

“…Interestingly, the analysis indicated that hot flush frequency appears to increase as the difference in temperatures between the hottest and coldest months increase. In other words, women living in seasonal climates may have greater sensitivity to temperature changes and this may explain, in part, why there is variation in hot flush frequency in different areas of the world 76 . The authors speculated that women in warmer climates report fewer hot flushes because they may have a reduced sensitivity to elevated temperatures or because they attribute warming sensations to the ambient warmth rather than hot flushes.…”

Somatic, mood, and vasomotor symptoms at midlife in relation to family structure and household workloads in Sylhet, Bangladesh

“…Factors associated with somatic, emotional, and vasomotor symptom experience at midlife include menopausal status (Avis et al 2001;Kuh et al 1997;Guthrie et al 2004;Melby et al 2011), smoking, socioeconomic status (Avis et al 1997), education (Schwingl et al 1994;Brambilla et al 1989), culture/cultural significance (Beyene 1989;Lock 1998;Robinson 1996;Melby et al 2005), diet (Nagata et al 2000) and environment/climate and seasonality (Sievert and Flanagan 2005). Studies of midlife have also suggested that psycho-social stress is a significant correlate of symptom frequencies in Canada (Kaufert et al 1992), the UK (Kuh et al 1997), the U.S. (McKinlay et al 1987;Thurston et al 2008), Spain (Sievert et al 2007b), Japan (Igarashi et al 2000), and Chile (Binfa et al 2004).…”