Table 1.
No. of Cases | No. of Person-Years | IRRa | 95% CI | IRRb | 95% CI | |
---|---|---|---|---|---|---|
Age at menarche, years | ||||||
≤11 | 123 | 195,800 | 1.01 | 0.81, 1.26 | 0.98 | 0.78, 1.22 |
12–13 | 230 | 363,091 | 1.00 | Reference | 1.00 | Reference |
≥14 | 98 | 132,709 | 1.14 | 0.90, 1.44 | 1.15 | 0.91, 1.46 |
P-trend | 0.25 | |||||
Age at menopause, yearsc | ||||||
<40 | 24 | 32,699 | 1.00 | Reference | 1.00 | Reference |
40–44 | 20 | 32,635 | 0.89 | 0.49, 1.61 | 0.92 | 0.51, 1.67 |
45–49 | 16 | 43,463 | 0.59 | 0.31, 1.12 | 0.65 | 0.34, 1.22 |
≥50 | 17 | 50,833 | 0.58 | 0.31, 1.12 | 0.60 | 0.31, 1.15 |
P-trend | 0.03 |
Abbreviations: CI, confidence interval; IRR, incidence rate ratio.
a Adjusted for age.
b Adjusted for age, education, geographic region, smoking, and body mass index.
c Restricted to postmenopausal women. Includes women who reported having undergone natural menopause or surgical menopause with removal of both ovaries.