Table 1. Baseline characteristics of study participants.
| Characteristics | BMI | |||
|---|---|---|---|---|
| Normal (<23 kg/m2) | Overweight (23–25 kg/m2) | Obese (≥25 kg/m2) | ||
| Age (yr) | 51.5±10.6 | 54.7±10.3 | 56.5±10.4 | |
| Age at menarche | ||||
| <15 years | 649,555 (24.5) | 311,311 (20.6) | 376,918 (19.4) | |
| 15–16 years | 1,000,585 (37.8) | 568,461 (37.7) | 709,674 (36.6) | |
| ≥17 years | 703,627 (26.6) | 491,009 (32.6) | 687,917 (35.5) | |
| Missing | 295,797 (11.2) | 136,882 (9.1) | 165,950 (8.6) | |
| Age at menopause | ||||
| Premenopause | 1,285,464 (48.5) | 584,477 (38.8) | 655,987 (33.8) | |
| <45 years | 77,549 (2.9) | 51,923 (3.4) | 81,942 (4.2) | |
| 45–52 years | 736,844 (27.8) | 515,903 (34.2) | 714,443 (36.8) | |
| ≥ 53 years | 217,939 (8.2) | 191,292 (12.7) | 287,751 (14.8) | |
| Missing | 331,768 (12.5) | 164,068 (10.9) | 200,336 (10.3) | |
| Delivery | ||||
| Nullipara | 291,726 (11.0) | 124,236 (8.2) | 139,635 (7.2) | |
| Para | 2,104,768 (79.4) | 1,272,189 (84.4) | 1,668,946 (86.0) | |
| Missing | 253,070 (9.6) | 111,238 (7.4) | 131,878 (6.8) | |
| Breast feeding | ||||
| Never | 461,092 (17.4) | 181,093 (12.0) | 175,361 (9.0) | |
| <1 year | 536,149 (20.2) | 295,555 (19.6) | 336,132 (17.3) | |
| ≥ 1 year | 1,388,895 (52.4) | 914,445 (60.7) | 1,289,924 (66.5) | |
| Missing | 263,428 (9.9) | 116,570 (7.7) | 139,042 (7.2) | |
| Oral contraceptive use | ||||
| Never | 1,969,875 (74.3) | 1,123,003 (74.5) | 1,434,555 (73.9) | |
| Ever | 423,389 (16.0) | 270,968 (18.0) | 370,700 (19.1) | |
| Missing | 256,300 (9.7) | 113,692 (7.5) | 135,204 (7.0) | |
| Family history of cancer | ||||
| No | 1,939,504 (73.2) | 1,142,825 (75.8) | 1,504,057 (77.5) | |
| Yes | 501,464 (18.9) | 280,098 (18.6) | 338,520 (17.4) | |
| Missing | 208,596 (7.9) | 84,740 (5.6) | 97,882 (5.0) | |
| Drinking frequency during the last 1 year | ||||
| No | 2,044,220 (77.2) | 1,196,744 (79.4) | 1,577,633 (81.3) | |
| 1 day/week | 365,867 (13.8) | 182,501 (12.1) | 208,724 (10.8) | |
| ≥2 day/week | 214,931 (8.1) | 113,871 (7.6) | 135,583 (7.0) | |
| Missing | 24,546 (0.9) | 14,547 (1.0) | 18,519 (1.0) | |
| Smoking | ||||
| Never | 2,501,378 (94.4) | 1,441,995 (95.6) | 1,853,413 (95.5) | |
| Ever | 134,321 (5.1) | 57,521 (3.8) | 76,654 (4.0) | |
| Missing | 13,865 (0.5) | 8,147 (0.5) | 10,392 (0.5) | |
| Vigorous physical activity | ||||
| No | 1,841,554 (69.5) | 1,034,814 (68.6) | 1,389,025 (71.6) | |
| 1–2 day/week | 435,974 (16.5) | 239,121 (15.9) | 277,335 (14.3) | |
| ≥3 day/week | 352,755 (13.3) | 223,056 (14.8) | 261,032 (13.5) | |
| Missing | 19,281 (0.7) | 10,672 (0.7) | 13,067 (0.7) | |
| Moderate physical activity | ||||
| No | 1,614,403 (60.9) | 925,499 (61.4) | 1,245,696 (64.2) | |
| 1–2 day/week | 514,755 (19.4) | 268,274 (17.8) | 318,461 (16.4) | |
| ≥3 day/week | 497,679 (18.8) | 300,644 (19.9) | 358,942 (18.5) | |
| Missing | 22,727 (0.9) | 13,246 (0.9) | 17,360 (0.9) | |
| Walking | ||||
| No | 869,356 (32.8) | 511,071 (33.9) | 707,277 (36.4) | |
| 1–3 days/week | 913,497 (34.5) | 488,657 (32.4) | 600,652 (31.0) | |
| 4–6 days/week | 543,164 (20.5) | 308,035 (20.4) | 369,369 (19.0) | |
| 7 days/week | 305,866 (11.5) | 189,568 (12.6) | 249,517 (12.9) | |
| Missing | 17,681 (0.7) | 10,332 (0.7) | 13,644 (0.7) | |
Values are presented as number (%) not otherwise specified.
BMI, body mass index.