Table 3.
Associations between breastfeeding and endometrial cancer risk among parous women in the pooled analysis
| Breastfeeding variables | Cases N(%)* |
Controls N(%)* |
Crude Pooled OR (95%CI) |
Adjusted Pooled OR† (95%CI) |
I2%‡ |
|---|---|---|---|---|---|
| Ever breast fed | |||||
| No | 3049 (33.9) | 5566 (32.3) | 1.00 | 1.00 | 4 |
| Yes | 5932 (66.1) | 11675 (67.7) | 0.82 (0.75–0.90) | 0.89 (0.81–0.98) | 5 |
| Total duration of breastfeeding (months) | |||||
| Never breastfed | 3049 (34.1) | 5566 (32.3) | 1.00 | 1.00 | |
| >0 to ≤3 | 1647 (18.4) | 3059 (17.8) | 0.98 (0.88–1.09) | 1.01 (0.91–1.12) | 18 |
| >3 to ≤6 | 915 (10.2) | 2017 (11.7) | 0.83 (0.74–0.92) | 0.84 (0.73–0.98) | 39 |
| >6 to ≤9 | 710 (7.9) | 1555 (9.0) | 0.81 (0.70–0.95) | 0.90 (0.77–1.05) | 32 |
| >9 to ≤12 | 667 (7.5) | 1000 (5.8) | 0.89 (0.73–1.07) | 0.96 (0.79–1.16) | 47 |
| >12 to ≤18 | 723 (8.1) | 1413 (8.2) | 0.82 (0.73–0.93) | 0.93 (0.82–1.05) | 0 |
| >18 to ≤24 | 506 (5.7) | 998 (5.8) | 0.74 (0.64–0.85) | 0.80 (0.69–0.93) | 3 |
| >24 to ≤30 | 248 (2.8) | 598 (3.5) | 0.66 (0.51–0.84) | 0.67 (0.51–0.87) | 40 |
| >30 to ≤36 | 179 (2.0) | 319 (1.9) | 0.65 (0.53–0.81) | 0.69 (0.54–0.88) | 0 |
| >36 | 309 (3.5) | 686 (4.0) | 0.58 (0.48–0.70) | 0.67 (0.53–0.83) | 18 |
| Per 3 months of total breastfeeding | 0.97 (0.96–0.98) | 0.97 (0.96–0.98) | 26 | ||
| Average duration of breastfeeding/child (months) § | |||||
| Never breastfed | 3049 (34.3) | 5566 (32.6) | 1.00 | 1.00 | |
| >0 to ≤3 | 2777 (31.3) | 5603 (32.9) | 0.99 (0.96–1.02) | 1.01 (0.98–1.03) | 0 |
| >3 to ≤6 | 1230 (13.9) | 2618 (15.4) | 0.92 (0.89–0.97) | 0.95 (0.91–0.99) | 25 |
| >6 to ≤9 | 844 (9.5) | 1649 (9.7) | 0.92 (0.88–0.97) | 0.93 (0.88–0.98) | 31 |
| >9 to ≤12 | 752 (8.5) | 1184 (6.9) | 0.90 (0.85–0.95) | 0.92 (0.86–0.97) | 7 |
| >12 to ≤18 | 225 (2.5) | 430 (2.5) | 0.86 (0.78–0.95) | 0.88 (0.79–0.97) | 22 |
| Average duration of breastfeeding/child breastfed§‖ (months) | |||||
| Never breastfed | 1793 (32.9) | 2335 (26.4) | 1.00 | 1.00 | |
| >0 to ≤3 | 1394 (25.6) | 2324 (26.3) | 0.98 (0.92–1.04) | 0.99 (0.93–1.05) | 29 |
| >3 to ≤6 | 798 (14.6) | 1674 (18.9) | 0.92 (0.86–0.98) | 0.93 (0.88–0.98) | 15 |
| >6 to ≤9 | 616 (11.3) | 1200 (13.6) | 0.90 (0.85–0.96) | 0.89 (0.83–0.95) | 17 |
| >9 to ≤12 | 673 (12.3) | 993 (11.2) | 0.88 (0.81–0.96) | 0.87 (0.80–0.95) | 21 |
| >12 to ≤18 | 176 (3.2) | 310 (3.5) | 0.86 (0.77–0.96) | 0.86 (0.78–0.95) | 1 |
OR, odds ratio; CI, confidence interval;
*
May not add to total due to missing data
†
Adjusted for age (years), parity (continuous), oral contraceptive duration (continuous; or ever use (yes/no)17,23, BMI (around reference age, continuous), education (level achieved or number of years).
‡
From random effects meta-analysis models. The I2% measures variation across studies that is due to heterogeneity rather than chance.
§
OR is for the risk change per child or per child breast fed.