Secular trends and associated factors of age at natural menopause in Taiwanese women

Abstract

Age at natural menopause (ANM) is considered an indicator for chronic disease and mortality risk in later life. Research suggests that ANM appears to vary across geographic regions and ethnicities. The aim of this study was to explore the secular trends and factors associated with ANM in Taiwanese women. We used data from three cross-sectional phases of the Nutrition and Health Survey in Taiwan. In all, 4,111 women aged 35 years and over were included. Information on ANM and sociodemographics, lifestyle, and health factors were collected using household questionnaires. A Cox proportional-hazards model was used to determine the association of ANM with relevant factors, and a life table method was used to estimate median ANM. Life table method estimated the median ANM to be 50 years. ANM was getting later for women born in younger cohorts (hazard ratio [HR] 0.87 per 10-year difference, 95% confidence interval [CI] 0.81-0.95). ANM was also later among women who achieved higher educational levels (HR 0.91 per one-category difference, 95% CI 0.86-0.96) and who had been married (HR 0.64, 95% CI 0.42-0.96). ANM occurred later for parous than for nulliparous women. Multivariable analysis found no significant associations of ANM with age at menarche, smoking, or alcohol drinking. The results suggest that women in the younger cohorts, with higher educational levels, and who are parous and married may have later ANM. The trend effect of secular time and educational levels on ANM may reflect the influences of socioeconomic/nutritional status in their childhood or throughout their lifetime.