Objectives: The outcome of interest was the assessment of age at natural menopause and the variables hypothesized as covariates of age at menopause were indicators of demographic and social status, characteristics of the reproductive history and lifestyle behaviour.
Methodology: Seven thousand one hundred and eighty-three women from all social strata of non-clinical population, and aged between 35 and 65 years were investigated in cross-sectional survey across Poland in 2000-2004. The demographic, social, lifestyle behaviour and reproductive history aspects of the menopause-specific questionnaire were examined. The non-parametric Kaplan-Meier cumulative survivorship estimates were used to assess the timing of natural menopause. Univariate and multivariate Cox proportional hazards regression models were used to assess the association of age at natural menopause with factors of interest and to estimate relevant relative risk (the hazard ratio) for earlier age at menopause.
Results: The overall median age at natural menopause was 51.25 years; 25th percentile 49; 75th percentile 54 years. Temporal changes in age at menopause were not demonstrated in the sample (p=0.9 for differences among age cohorts). Univariate Cox models were first fitted to the age at natural menopause for all covariates singly. The findings revealed that marital status, living environment, employment, BMI, age at first live birth delivered by a woman, breastfeeding, physical activity, smoking amount, and consumption of alcohol were not associated with age at menopause (p>0.05). The multiple Cox model revealed that early menarche, short menstrual cycle length, smoking cigarettes, a low level of education, and a negative health perception were associated with younger age at menopause (p<0.01). Use of oral contraceptives and parity were associated with later menopause (p<0.01).
Conclusion: The present study provides an estimate of median age at natural menopause in Poland that may be used as a measure of health for the growing number of Polish women whose survival is calculated at 30 years after menopause. This study has revealed that the pattern of relationship between age at menopause and the study factors reflects its population-specific character for its social and cultural backgrounds, socio-economic status, and social behaviours.