Associations of age at natural menopause and occupations in Chinese female workers: a cross-sectional study

AIMS To investigate the impact of occupation types on age at natural menopause. METHODS This is a nation-wide cross-sectional study based on 17,948 female workers aged over 40, who come from different industries or organizations. A face-to-face standardized questionnaire was conducted in all participants with the help of occupational hygienists. Occupational titles were coded according to the International Standard Classification of Occupations (2008) (ISCO08). Cox regression model was used to assess the association between each independent occupation and menopausal timing. Models were adjusted for marriage, education, average annual family income, parity, cigarette smoking, alcohol consumption. RESULTS Higher risks of earlier age at natural menopause was found among legislators and senior officials (ISCO Minor group:111, HR = 2.328, P < 0.001), among other health associated professionals (ISCO Minor group: 325, HR = 1.477, P = 0.003), the workers involved in mining and mineral processing (ISCO Minor group: 811, HR = 1.515, P = 0.048) and metal processing and finishing (ISCO Minor group: 812, HR = 1.722, P < 0.001). Reduced risks of earlier age at natural menopause, including: finance professionals (ISCO Minor group: 241, HR = 0.751, P = 0.021), manufacturing and construction supervisors (ISCO Minor group: 312, HR = 0.477, P = 0.002), administrative and specialized secretaries (ISCO Minor group: 334, HR = 0.788, P = 0.045), cleaners and helpers (ISCO Minor group: 911, HR = 0.633, P = 0.01). CONCLUSIONS This is the first study to address the influence of occupation types on reproductive aging, showing some specific occupations could be associated with age at natural menopause. Further investigations are necessary to clarify whether it is chance finding or a true association.