Table 3.
Subgroup analyses based on study quality factors for the association between solar UVR exposure and the risk of developing breast cancer.
| Subgroup | Estimates (n) | Relative risk (95% CI) | (%) | Meta-regression (p-value) |
|---|---|---|---|---|
| vs. | ||||
| Study design | 0.65 | |||
| Prospective cohort | 4 | 0.82 (0.73, 0.92) | 65.2 | |
| Case–control | 5 | 0.85 (0.75, 0.97) | 80.3 | |
| Newcastle-Ottawa scores | 0.74 | |||
| Good | 5 | 0.81 (0.72, 0.92) | 81.7 | |
| Fair | 2 | 0.92 (0.82, 1.03) | 0.0 | |
| Poor | 2 | 0.83 (0.59, 1.15) | 30.3 | |
| Control for confounding | 0.11 | |||
| Adequate | 5 | 0.89 (0.82, 0.97) | 65.9 | |
| Moderate | 2 | 0.74 (0.61, 0.89) | 66.1 | |
| Insufficient | 2 | 0.82 (0.57, 1.18) | 73.3 | |
| 1 to vs. | ||||
| Study design | 0.79 | |||
| Prospective cohort | 3 | 0.84 (0.78, 0.91) | 0.0 | |
| Case–control | 4 | 0.80 (0.67, 0.96) | 57.0 | |
| Newcastle-Ottawa scores | 0.81 | |||
| Good | 5 | 0.82 (0.74, 0.90) | 35.8 | |
| Fair | 2 | 0.84 (0.71, 1.00) | 0.0 | |
| Poor | 0 | NA | NA | |
| Control for confounding | 0.11 | |||
| Adequate | 5 | 0.85 (0.80, 0.91) | 0.0 | |
| Moderate | 2 | 0.72 (0.59, 0.89) | 18.1 | |
| Insufficient | 0 | NA | NA | |
| vs. | ||||
| Study design | 0.89 | |||
| Prospective cohort | 3 | 0.86 (0.79, 0.93) | 12.1 | |
| Case–control | 4 | 0.82 (0.66, 1.02) | 88.8 | |
| Newcastle-Ottawa scores | 0.6 | |||
| Good | 5 | 0.81 (0.70, 0.94) | 79.2 | |
| Fair | 2 | 0.88 (0.77, 1.00) | 32.3 | |
| Poor | 0 | NA | NA | |
| Control for confounding | 0.17 | |||
| Adequate | 5 | 0.87 (0.77, 0.98) | 72.2 | |
| Moderate | 2 | 0.74 (0.63, 0.88) | 45.1 | |
| Insufficient | 0 | NA | NA | |
| Ambient UVR (high exposure vs. low exposure) | ||||
| Study design | 0.47 | |||
| Prospective cohort | 7 | 1.01 (0.93, 1.10) | 59.7 | |
| Case–control | 1 | 0.91 (0.72, 1.16) | NA | |
| Newcastle-Ottawa scores | 0.06 | |||
| Good | 4 | 0.94 (0.85, 1.04) | 46.1 | |
| Fair | 2 | 1.20 (1.02, 1.43) | 0.0 | |
| Poor | 1 | 1.03 (0.97, 1.09) | 0.0 | |
| Control for confounding | 0.29 | |||
| Adequate | 5 | 0.97 (0.86, 1.09) | 24.0 | |
| Moderate | 2 | 1.05 (0.96, 1.16) | 58.2 | |
| Insufficient | 0 | NA | NA | |
Note: Relative risk estimates for each subgroup were estimated with DerSimonian and Laird random-effect models. Meta-regression was used to determine whether there were significant differences in the risk of breast cancer by exposure to UVR in different study quality subgroups. NA, not applicable; UVR, ultraviolet radiation.