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.

Family-level leaf nitrogen and phosphorus stoichiometry of global terrestrial plants.

Leaf nitrogen (N) and phosphorus (P) concentrations are critical for photosynthesis, growth, reproduction and other ecological processes of plants. Previous studies on large-scale biogeographic patterns of leaf N and P stoichiometric relationships were mostly conducted using data pooled across taxa, while family/genus-level analyses are rarely reported. Here, we examined global patterns of family-specific leaf N and P stoichiometry using a global data set of 12,716 paired leaf N and P records which includes 204 families, 1,305 genera, and 3,420 species. After determining the minimum size of samples (i.e., 35 records), we analyzed leaf N and P concentrations, N:P ratios and N∼P scaling relationships of plants for 62 families with 11,440 records. The numeric values of leaf N and P stoichiometry varied significantly across families and showed diverse trends along gradients of mean annual temperature (MAT) and mean annual precipitation (MAP). The leaf N and P concentrations and N:P ratios of 62 families ranged from 6.11 to 30.30 mg g-1, 0.27 to 2.17 mg g-1, and 10.20 to 35.40, respectively. Approximately 1/3-1/2 of the families (22-35 of 62) showed a decrease in leaf N and P concentrations and N:P ratios with increasing MAT or MAP, while the remainder either did not show a significant trend or presented the opposite pattern. Family-specific leaf N∼P scaling exponents did not converge to a certain empirical value, with a range of 0.307-0.991 for 54 out of 62 families which indicated a significant N∼P scaling relationship. Our results for the first time revealed large variation in the family-level leaf N and P stoichiometry of global terrestrial plants and that the stoichiometric relationships for at least one-third of the families were not consistent with the global trends reported previously. The numeric values of the family-specific leaf N and P stoichiometry documented in the current study provide critical synthetic parameters for biogeographic modeling and for further studies on the physiological and ecological mechanisms underlying the nutrient use strategies of plants from different phylogenetic taxa.