Table 2. Summary risk estimates of the association between menarcheal age and endometrial cancer risk, oldest versus youngest category.
| No. of | Summary RR | I2 | Ph* | Ph** | |
|---|---|---|---|---|---|
| studies | (95% CI) | Value (%) | |||
| Overall | 8 | 0.68 (0.58–0.81) | 41.9 | 0.099 | — |
| Subgroup analyses | |||||
| Duration of follow-up | 0.085 | ||||
| <10y | 3 | 0.78 (0.68–0.89) | 0 | 0.674 | |
| ≥10y | 5 | 0.56 (0.42–0.74) | 37.2 | 0.173 | |
| Number of cases | 0.281 | ||||
| <400 | 4 | 0.74 (0.65–0.84) | 62.4 | 0.046 | |
| ≥400 | 4 | 0.55 (0.33–0.90) | 0 | 0.563 | |
| Exposure Assessment | 0.992 | ||||
| Trained interviewer | 1 | 1.01 (0.82–1.24) | N/A | N/A | |
| Self-administered questionnaire | 7 | 0.68 (0.57–0.81) | 50.2 | 0.061 | |
| Study population | 0.232 | ||||
| Non-American | 3 | 0.58 (0.41–0.81) | 62.2 | 0.071 | |
| American | 5 | 0.77 (0.67–0.90) | 0 | 0.421 | |
| Adjustment for confounders or important risk factors | |||||
| Body mass index | 0.057 | ||||
| Yes | 4 | 0.77 (0.68–0.88) | 0 | 0.849 | |
| No | 4 | 0.48 (0.36–0.63) | 0 | 0.612 | |
| Parity | 0.710 | ||||
| Yes | 5 | 0.69 (0.55–0.86) | 57.0 | 0.054 | |
| No | 3 | 0.64 (0.45–0.91) | 20.3 | 0.285 | |
| Oral contraceptive use | 0.085 | ||||
| Yes | 3 | 0.80 (0.69–0.93) | 0 | 0.900 | |
| No | 5 | 0.56 (0.42–0.74) | 41.8 | 0.143 | |
| Exogenous hormones use | 0.085 | ||||
| Yes | 3 | 0.80 (0.69–0.93) | 0 | 0.900 | |
| No | 5 | 0.56 (0.42–0.74) | 41.8 | 0.143 | |
| Menopause status | 0.085 | ||||
| Yes | 3 | 0.80 (0.69–0.93) | 0 | 0.900 | |
| No | 5 | 0.56 (0.42–0.74) | 41.8 | 0.143 | |
| Smoking status | 0.057 | ||||
| Yes | 4 | 0.77 (0.68–0.88) | 0 | 0.849 | |
| No | 4 | 0.48 (0.36–0.63) | 0 | 0.612 | |
RR: relative risk; CI: confidence interval; N/A: not available.
*P value for heterogeneity within each subgroup.
**P value for heterogeneity between subgroups with meta-regression analysis.