Table 3.
Duration and Cessation of IUD Use and Ovarian Cancer Risk, among users, the Shanghai Women’s Health Study
| Total | Cases | Non-Cases | HR1 | P | HR2 | P | |
|---|---|---|---|---|---|---|---|
| Among IUD Users | |||||||
| Years of Use* | |||||||
| <12 years | 9235 (23.7%) | 31 (34.1%) | 9204 (23.6%) | 1 (reference) | – | 1 (reference) | – |
| 12≤ to <20 years | 8622 (22.1%) | 20 (22.0%) | 8602 (22.1%) | 0.71 (0.43–1.15) | 0.16 | 0.67 (0.41–1.10) | 0.11 |
| 20≤ to <24 years | 9811 (25.1%) | 20 (22.0%) | 9791 (25.1%) | 0.65 (0.39–1.07) | 0.09 | 0.61 (0.37–1.02) | 0.06 |
| ≥24 years | 11386 (29.2%) | 20 (22.0%) | 11366 (29.2%) | 0.59 (0.35–0.98) | 0.04 | 0.56 (0.33–0.93) | 0.02 |
| P-value for trend | 0.02 | 0.01 | |||||
| IUD Removal | |||||||
| Removed by Interview | 16023 (41.0%) | 48 (52.8%) | 15975 (41.0%) | 1 (reference) | – | 1 (reference) | – |
| Present at Interview | 23031 (59.0%) | 43 (47.3%) | 22988 (59.0%) | 0.58 (0.37–0.91) | 0.02 | 0.55 (0.35–0.88) | 0.01 |
1
Adjusted for age at recruitment
2
Adjusted for age at recruitment, education, years of ovulation, irregular ovulatory cycles (yes/no), first-degree family history of cancer (yes/no), BMI, exercised regularly in past 5 years (yes/no), and other contraceptive methods (never/ever)
*
Years of use if IUD removed, or until age at interview plus two years for post-menopausal women or to age 53 (mean plus one standard deviation) for pre-menopausal women with IUDs present at interview