Factors associated with age at natural menopause among elderly women in São Paulo, Brazil.

OBJECTIVES: To analyze factors associated with age at natural menopause in elderly women who are part of the Health, Well-Being and Aging Study- which is a representative sample of elderly residents of the municipality of São Paulo, Brazil.

METHODS: Multivariate Cox proportional-hazards analysis using data from a total of 1,415 women with natural menopause. We included 163 women with hysterectomy, oophorectomy, and estrogen therapy as censored data.

RESULTS: The median age of natural menopause was 50 years. In the multivariate Cox proportional hazards, smoking was associated with earlier age at natural menopause for the three cohorts (2000, 2006, and 2010). Current smokers had a 35% higher risk of earlier natural menopause (hazard ratio [HR] 1.35, 95% confidence interval [CI] 1.12, 1.62) and former smokers had a 27% higher risk of earlier natural menopause (HR 1.27, 95% CI 1.09, 1.50), in comparison with never-smokers. Women with 8 years or more of formal education had a 33% lower risk of earlier natural menopause (HR 0.67, 95% CI 0.50, 0.89) than women with no education, and women who were separated, widowed, or divorced had a 15% higher risk of earlier natural menopause (HR 1.15, 95% CI 1.00, 1.31) in comparison with married women. Marital status and parity were associated with later age at natural menopause only in 2006.

CONCLUSIONS: We found significant associations of age at natural menopause with reproductive and lifestyle factors similar to some studies of women from developed countries.