Table 1. Characteristics of the study population at recruitment, and details of follow-up, by tubal ligation status.
|
Tubal ligation |
||
|---|---|---|
| No | Yes | |
|
Characteristics | ||
| Number of women | 984 059 | 294 724 |
| Mean (s.d.) age at recruitment (years) | 56.3 (5.0) | 55.4 (4.3) |
| Socioeconomic status, lowest quintile, % (n) | 18.1 (176 985) | 25.1 (73 503) |
| Nulliparous, % (n) | 13.3 (130 818) | 2.6 (7558) |
| Ever use of oral contraceptive pill, % (n) | 56.5 (551 799) | 69.5 (202 511) |
| Ever use of menopausal hormones, % (n) | 47.5 (463 250) | 58.2 (169 199) |
| Hysterectomy, % (n) | 21.9 (215 280) | 29.1 (84 514) |
| Mean (s.d.) body mass index (kg m−2) | 26.1 (4.6) | 26.7 (4.9) |
| Current smoker, % (n) | 18.5 (171 593) | 26.9 (74 647) |
| Strenuous exercise ⩾once/week, % (n) | 39.5 (375 006) | 37.1 (105 032) |
| Alcohol intake, ⩾7 units/week, % (n) | 23.3 (227 830) | 24.8 (72 471) |
|
Follow-up for cancer incidence | ||
| Woman-years of follow-up (100 000 s) | 136.0 | 40.5 |
| Mean (s.d.) follow-up time per woman | 13.8 (3.4) | 13.8 (3.3) |
| Number of incident cancers | 129 531 | 37 899 |
Abbreviations: n=Number of women; s.d.=standard deviation.
Notes: Means and percentages are calculated excluding missing values for the variable of interest.