Age at natural menopause and associated factors with early and late menopause among Chinese women in Zhejiang province: A cross-sectional study

Objectives Menopause is a significant life transition for women, impacting their physical and psychological health. The age at natural menopause (ANM) and its associated factors have differed by race and region. This study aimed to investigate ANM and associated factors of early and late menopause among Chinese women in Zhejiang province. Methods A cross-sectional study was conducted using a multi-stage stratified cluster sampling method to recruit 8,006 women aged 40-69 years who had resided in Zhejiang province for over 6 months between July 2019 and December 2021. Self-reported ANM and sociodemographics, lifestyle behaviors, reproductive history, and health-related factors were collected using questionnaires in face-to-face surveys. ANM were categorized into three groups: early menopause (<45 years), normal menopause (45-54 years), and late menopause (>= 55 years). Kaplan-Meier survival analysis was utilized to calculate the median ANM. Multivariable multinomial logistic regression was employed to explore the associated factors of early menopause and late menopause. Results A total of 6,047 women aged 40-69 years were included for survival analysis, with 3,176 of them for the regression analysis. The overall median ANM was 51 years (Inter-quartile range [IQR]: 51-52). Women who were smokers (odds ratio [OR]:4.54, 95% confidence interval [CI]:1.6-12.84), had irregular menstrual cycles (OR:1.78, 95% CI:1.12-2.83) and hypertension (OR:1.55, 95% CI:1.09-2.21) had a higher odds ratio of early menopause, while central obesity (OR:1.33, 95% CI:1.03-1.73) and hyperlipidemia (OR:1.51, 95% CI:1.04-2.18) were factors associated with late menopause. Conclusions This study revealed the associations between ANM and various factors among Chinese women. These factors included socio-demographic factors such as age; life behavior factors like current or prior smoking status; reproductive history factors such as irregular menstrual cycles, miscarriages, and breastfeeding; and health-related factors like central adiposity, hypertension, and hyperlipidemia. These findings provided a basis for understanding factors associated with ANM.