Table 3.
Odds ratios (ORs) and 95% confidence intervals (CIs) of quantitative IUD variables and endometrial cancer risk according to IUD type
| Inert IUD users | Copper IUD users | |||||
|---|---|---|---|---|---|---|
| Cases | Controls | Cases | Controls | |||
| n (%) | OR (95% CI)1 | n (%) | OR (95% CI)1 | |||
| Age at first IUD use2 | ||||||
| Never user | 1521 (82.3) | 1895 (80.5) | Ref | 1521 (94.3) | 1895 (83.4) | Ref |
| <25 | 9 (0.5) | 28 (1.2) | 0.23 (0.10, 0.52) | 22 (1.4) | 83 (3.6) | 1.11 (0.65, 1.91) |
| 25–29 | 128 (6.9) | 146 (6.2) | 0.68 (0.51, 0.91) | 38 (2.4) | 119 (5.2) | 1.32 (0.84, 2.07) |
| 30–34 | 144 (7.8) | 198 (8.4) | 0.61 (0.47, 0.80) | 19 (1.2) | 91 (4.0) | 0.78 (0.44, 1.39) |
| ≥35 | 45 (2.4) | 87 (3.7) | 0.49 (0.33, 0.72) | 10 (0.6) | 69 (3.0) | 0.52 (0.25, 1.10) |
| ptrend3 | 0.43 | 0.08 | ||||
| Age at last IUD use4 | ||||||
| Never user | 1177 (78.3) | 1312 (74.1) | Ref | 1177 (92.7) | 1312 (77.7) | Ref |
| <30 | 22 (1.5) | 31 (1.7) | 0.73 (0.40, 1.32) | 16 (1.3) | 66 (3.9) | 0.98 (0.52, 1.82) |
| 30–39 | 87 (5.8) | 95 (5.4) | 0.85 (0.60, 1.19) | 39 (3.1) | 130 (7.7) | 1.30 (0.83, 2.03) |
| 40–44 | 49 (3.3) | 88 (5.0) | 0.44 (0.29, 0.66) | 16 (1.3) | 81 (4.8) | 0.83 (0.45, 1.54) |
| ≥45 | 162 (10.8) | 241 (13.6) | 0.56 (0.44, 0.72) | 18 (1.4) | 80 (4.7) | 0.82 (0.45, 1.50) |
| ptrend3 | 0.03 | 0.91 | ||||
| Duration of use (years)5 | ||||||
| Never user | 2570 (88.7) | 2439 (84.2) | Ref | 2570 (96.5) | 2439 (86.8) | Ref |
| < 1 | 20 (0.7) | 33 (1.1) | 0.69 (0.39, 1.24) | 0 (0.0) | 10 (0.4) | 0.94 (0.22, 4.04) |
| 1–4 | 50 (1.7) | 65 (2.2) | 0.82 (0.55, 1.22) | 36 (1.3) | 122 (4.3) | 1.15 (0.72, 1.83) |
| 5–9 | 50 (1.7) | 53 (1.8) | 0.82 (0.53, 1.25) | 18 (0.7) | 79 (2.8) | 0.98 (0.55, 1.76) |
| ≥10 | 200 (6.9) | 307 (10.6) | 0.53 (0.42, 0.67) | 38 (1.4) | 152 (5.4) | 1.03 (0.65, 1.61) |
| ptrend3 | 0.06 | 0.55 | ||||
| Time since last IUD use (years)6 | ||||||
| Never user | 1098 (77.1) | 1027 (69.1) | Ref | 1098 (99.3) | 1027 (98.8) | Ref |
| Within 1 year of study entry | 99 (6.9) | 187 (12.6) | 0.38 (0.28, 0.52) | 0 (0.0) | 1 (0.1) | NE |
| 1–4 | 68 (4.8) | 76 (5.1) | 0.71 (0.48, 1.03) | 1 (0.9) | 2 (0.2) | 2.52 (0.20, 31.15) |
| 5–9 | 50 (3.5) | 58 (3.9) | 0.71 (0.46, 1.08) | 5 (0.4) | 2 (0.2) | 6.33 (1.03, 38.96) |
| ≥10 | 103 (7.2) | 134 (9.0) | 0.77 (0.57, 1.04) | 2 (0.2) | 6 (0.6) | 0.75 (0.14, 3.96) |
| ptrend3 | <0.0001 | NE | ||||
Adjusted for age (continuous), race (White, Black, Asian, Other), BMI (< 25kg/m2, 25–30 kg/m2, ≥30 kg/m2), age at menarche (<11, 11–12, 13–14, ≥15), duration of oral contraceptive use (never, <5, 5–9, ≥10 years), parity/age at last birth (nulliparous, 1–2 births and <25, 1–2 births and 25–29, 1–2 births and 30–34, 1–2 births and ≥35, ≥3 births and <25, ≥3 births and 25–29, ≥3 births and 30–34, ≥3 births and ≥35), menopausal status (premenopausal, postmenopausal), any menopausal hormone use (never, ever), smoking status (never, former, current), and stratified by study
Available in CTS, SECS, US, WLHS
p-value for trend was calculated using the Wald test for the ordinal variable based on the categories shown among IUD users
Available in SECS, US, WLHS
Available in ANECS, CTS, SECS, US, WLHS
Available in SECS and US
NE: Not estimable