Table 3.
Odds Ratios for Non-Hodgkin Lymphoma According to Birth Order/Sibship Size in a Pooled Analysis of Results From 18 Non-Hodgkin Lymphoma Case-Control Studies Within the International Lymphoma Epidemiology Consortium (InterLymph), 1983–2005
| Familial Structure Variable | No. of Cases | No. of Controls | Odds Ratioa | 95% Confidence Interval | Heterogeneity |
||
| No. of Studies | P Value | I2, % | |||||
| Birth order | |||||||
| Firstborn | 3,610 | 4,579 | 1.00 | ||||
| Second-born | 2,595 | 3,311 | 1.01 | 0.92, 1.10 | 14 | 0.19 | 24.5 |
| Third-born | 1,520 | 1,841 | 1.05 | 0.93, 1.20 | 14 | 0.02 | 48.1 |
| Fourth-born | 816 | 977 | 1.12 | 0.96, 1.30 | 14 | 0.05 | 42.0 |
| Fifth-born or higher | 1,228 | 1,401 | 1.12 | 0.95, 1.32 | 14 | <0.01 | 60.9 |
| P-trend | 0.082 | ||||||
| Sibship size | |||||||
| Only child | 1,283 | 1,581 | 1.00 | ||||
| No. of other siblings | |||||||
| 1 | 2,820 | 3,591 | 1.02 | 0.93, 1.12 | 18 | 0.83 | 0.0 |
| 2 | 2,668 | 3,290 | 1.06 | 0.96, 1.16 | 18 | 0.72 | 0.0 |
| 3 | 1,902 | 2,314 | 1.04 | 0.88, 1.21 | 18 | 0.02 | 46.7 |
| 4 | 1,248 | 1,591 | 1.01 | 0.87, 1.18 | 18 | 0.09 | 32.8 |
| ≥5 | 2,720 | 3,235 | 1.10 | 0.93, 1.29 | 18 | 0.01 | 50.9 |
| P-trend | 0.313 | ||||||
a
Odds ratios and 95% confidence intervals were computed using a 2-stage random-effects model, adjusted for age (in 5-year intervals), sex, and study center.