An Explanation for Variation in Age at Menopause in Developing Countries Based on the Second National Integrated Micronutrient Survey in Iran.

Background: It is reported that women in developing countries reach menopause earlier compared to developed countries. This seems to be due to underestimation of age at menopause as pre-menopause women who will reach menopause at older ages are commonly excluded in cross-sectional settings. In this study, we propose an estimation method which can deal with this bias. We also assessed major determinants of menopause.

Methods: The second national integrated micronutrient survey in Iran completed in 2015 is a population-based study with a nationally representative sample of 4,898 Iranian women aged 50 to 60 years. We used data on menopause status and menopausal age (asked retrospectively) to estimate the median survival time. We also used Logistic regression to model menopausal status on the current age and to estimate the median age, at which 50% of women will experience menopause. Demographic, lifestyle, and anthropometric determinants were also examined.

Results: The estimated age at menopause was 51.2 (51.0-51.3) years in the logistic model and 50.5 (48.1, 53.7) years in survival analysis. In both models, the age at menopause was significantly lower among rural and underweight women. In addition, survival analysis showed that smokers and women with smaller family size had significantly lower age at menopause.

Conclusion: While many studies stress a gap in age at menopause between developed and developing countries, this study with a reliable estimation method showed that such a gap might originate from an underestimation of age at menopause in developing countries rather than a real difference.