Age at menarche, age at menopause, reproductive years and risk of fatal stroke occurrence among Chinese women: the Guangzhou Biobank Cohort Study

Background: The relationship between women's reproductive characteristics and stroke events is unclear. We aimed to investigate age at menarche, age at menopause and number of reproductive years in relation to fatal stroke occurrence in the Guangzhou Biobank Cohort Study.

Methods: In total, 16,504 postmenopausal women without stroke, heart disease or a cancer history at baseline were included and followed up for a median of 12.0 years. After review of available records, 222 stroke deaths were recorded. Cox proportional hazards regression was used to assess the associations between the risk of fatal stroke occurrence and age at menarche, age at menopause and number of reproductive years.

Results: In the whole cohort, compared with those aged 15 years at menarche, an increased risk of fatal stroke among women at menarche showed respectively in those aged 12 years (aHR (adjusted hazard ratio) = 1.86, 95% confidence interval (CI) 0.96-3.60), aged 13 years (aHR = 1.69, 95% CI 0.98-2.92), aged 17 years (aHR = 1.83, 95% CI 1.10-3.05) and aged ≥ 18 years (aHR = 1.66, 95% CI 1.03-2.70), wherein the associations revealed an atypically U-shaped; similar U-shaped association to the cohort of postmenopausal women born before 1940 released a range of incremental risks of fatal stroke in women at menarche aged ≤ 12 years (aHR = 3.68, 95% CI 1.68-8.05), aged 13 years (aHR = 2.11, 95% CI 1.02-4.34), aged 14 years (aHR = 2.07, 95% CI 1.04), aged 17 years (aHR = 2.30, 95% CI 1.20-4.39) and aged 18 years (aHR = 2.50, 95% CI 1.37-4.57), respectively. Compared with menopausal women aged 51-52 years, those aged < 43 years at menopause had an increased risk for fatal stroke among postmenopausal women born in and after 1940 (aHR = 1.64, 95% CI 0.97-2.78) and postmenopausal women born before 1940 (aHR = 1.97, 95% CI 1.05-3.69). Additionally, compared with those with 32-34 reproductive years, women with ≤ 28 reproductive years had an increased risk for fatal stroke in the whole cohort (aHR = 1.91, 95% CI 1.28-2.86) and the cohort of postmenopausal women born before 1940 (aHR = 1.79, 95% CI 1.15-2.80).

Conclusions: Younger and older age at menarche, younger age at menopause and fewer reproductive ages were related to an increased risk of fatal stroke in postmenopausal women.