Table 3. Summary risk estimates of the association between menarcheal age and endometrial cancer risk, dose-response analysis of per 2 year delay.

	No. of	Summary RR	I2	Ph*	Ph**
	studies	(95% CI)	Value (%)
Overall	6	0.96 (0.94–0.98)	45.7	0.101	—
Subgroup analyses
Duration of follow-up					0.303
<10y	2	0.97 (0.95–0.99)	44.7	0.179
≥10y	4	0.95 (0.91–0.98)	33.7	0.210
Number of cases					0.067
<400	3	0.92 (0.89–0.96)	0	0.868
≥400	3	0.97 (0.96–0.99)	0	0.388
Exposure Assessment					0.680
Trained interviewer	1	1.01 (0.82–1.24)	N/A	N/A
Self-administered questionnaire	6	0.96 (0.94–0.98)	55.8	0.066
Study population					0.259
Non-American	2	0.95 (0.91–0.98)	56.3	0.130
American	4	0.98 (0.96–0.99)	7.5	0.356
Adjustment for confounders or important risk factors
Body mass index					0.067
Yes	3	0.97 (0.96–0.99)	0	0.388
No	3	0.92 (0.89–0.96)	0	0.868
Parity					0.652
Yes	3	0.96 (0.94–0.99)	66.5	0.051
No	3	0.96 (0.93–0.98)	0	0.469
Oral contraceptive use					0.080
Yes	2	0.98 (0.97–0.99)	0	0.560
No	4	0.95 (0.92–0.97)	12.2	0.332
Exogenous hormones use					0.080
Yes	2	0.98 (0.97–0.99)	0	0.560
No	4	0.95 (0.92–0.97)	12.2	0.332
Menopause status					0.080
Yes	2	0.98 (0.97–0.99)	0	0.560
No	4	0.95 (0.92–0.97)	12.2	0.332
Smoking status					0.067
Yes	3	0.97 (0.96–0.99)	0	0.388
No	3	0.92 (0.89–0.96)	0	0.868

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.