Regional differences in age at menopause between Korean-Korean and Korean-Chinese.

Abstract:  OBJECTIVE: To evaluate the difference in age at menopause between Korean-Korean (KK) women and Korean-Chinese (KC) women. DESIGN: A total of 1,972 participants were recruited: 961 postmenopausal women living in Korea, and 1,011 second- or third-generation emigrants to China. A structured questionnaire was used that included current age (at interview), age at menopause, weight, height, duration of education, socioeconomic status (SES), smoking, alcohol intake, number of children and abortions, etc. For every independent variable, the effect of regional difference (ie, living in Korea or China) on age at menopause was analyzed. Student's t test and chi2 test were applied as appropriate, and multiple regression analyses were performed for significant variables. RESULTS: Age at menopause was significantly higher in KK than KC (49.3 +/- 3.5 y vs 48.9 +/- 3.1 y, P = 0.011). Body mass index (BMI) and number of abortions were also higher in KK (23.3 +/- 2.7 vs 23.1 +/- 2.6, P = 0.021; 1.3 +/- 1.7 vs 0.2 +/- 0.7, P = 0.0001). Duration of education was significantly longer in KK. Smokers showed a significantly earlier menopause onset. BMI was significantly and positively correlated with age at menopause, whereas current SES was negatively correlated. When regional differences were assessed in each categorized subgroup, age at menopause showed a significant difference, too. After adjusting for age, SES, BMI, smoking, and number of children, onset of menopause was still earlier in KC (P = 0.0001, R = 0.037). CONCLUSION: KK women were found to have a later onset of menopause than KC women, and our results suggest that, apart from the well-known genetic influence, environmental effects play a significant role in determining age at menopause.