Table 2.
Meta-analysis of the effect of the exposure to DDT on the risk of breast cancer according to subgroup
| Studies included | No. of Studies | OR | 95% CI | Heterogeneity |
Egger’s test (p for bias) | |
|---|---|---|---|---|---|---|
| p-value | I2 (%) | |||||
| Type of study design | ||||||
| Hospital CC | 16 | 1.02 | 0.91 to 1.15 | 0.183 | 24.0 | 0.780 |
| Population CC | 11 | 1.19 | 0.99 to 1.44 | 0.004 | 61.3 | 0.212 |
| Nested CC | 10 | 0.90 | 0.81 to 1.01 | 0.554 | 0.0 | 0.274 |
| Study years | ||||||
| 2000s | 2 | 1.28 | 0.44 to 3.71 | 0.001 | 91.5 | – |
| 1990s | 27 | 1.03 | 0.94 to 1.24 | 0.034 | 35.9 | 0.169 |
| 1980s | 4 | 0.87 | 0.69 to 1.09 | 0.575 | 0.0 | 0.908 |
| 1970s | 2 | 0.92 | 0.73 to 1.17 | 0.808 | 0.0 | – |
| 1960s | 2 | 1.30 | 0.95 to 1.77 | 0.962 | 0.0 | – |
| Type of biologic specimen | ||||||
| Serum | 24 | 1.07 | 0.93 to 1.11 | 0.006 | 47.0 | 0.365 |
| Plasma | 5 | 0.97 | 0.85 to 1.11 | 0.325 | 14.1 | 0.910 |
| Adipose tissue | 8 | 0.98 | 0.83 to 1.16 | 0.141 | 36.0 | 0.228 |
| Country | ||||||
| North America | 22 | 1.01 | 0.92 to 1.10 | 0.185 | 21.0 | 0.524 |
| Europe | 8 | 1.02 | 0.81 to 1.29 | 0.010 | 62.0 | 0.246 |
| Asia | 3 | 0.92 | 0.63 to 1.36 | 0.226 | 32.8 | 0.900 |
| South America | 4 | 1.20 | 0.78 to 1.83 | 0.012 | 72.8 | 0.707 |
CC = case–control study; CI = confidence interval; OR = odds ratio.