Joint Associations of Actual Age and Genetically Determined Age at Menarche With Risk of Mortality.

Importance Previous studies have shown an association between actual age at menarche and risk of all-cause mortality; however, the results are inconsistent, and no study has analyzed the joint associations between genetic susceptibility and actual age at menarche with the risk of mortality in prospective cohorts. Objectives To investigate joint associations of actual age and genetically determined age at menarche with risk of all-cause mortality. Design, Setting, and Participants This prospective cohort study was conducted using data from the UK Biobank population across the United Kingdom from March 13, 2006, to October 1, 2010. A total of 264 546 women aged between 39 and 71 years with actual menarcheal age were included in this study; 246 676 of these women had genetic data available. Actual age at menarche was obtained from the touchscreen questionnaire at recruitment from 2006 to 2010. Genetically determined age at menarche was assessed by a genetic risk score. Statistical analysis was performed from August 22 to December 12, 2019. Exposure Age at menarche. Main Outcomes and Measures A multivariable Cox proportional hazards regression model was used to assess associations of actual or genetically determined age at menarche with risk of all-cause mortality. Results The mean (SD) age of the study population at baseline was 56.4 (8.0) years, and the mean (SD) age at menarche included in the analyses was 13.0 (1.6) years. During a median of 9.0 years (range, 8.3-9.7 years) of follow-up, 7761 deaths were documented among the women with actual age at menarche, and 7054 deaths were documented among the women with genetically determined age at menarche. Both the actual age at menarche and the genetically determined age at menarche showed a U-shaped association with the risk of all-cause mortality (lowest actual age [<12 years] vs reference age [15 years]: hazard ratio [HR], 1.16 [95% CI, 1.07-1.26]; highest actual age [≥16 years] vs reference age [15 years]: HR, 1.17 [95% CI, 1.05-1.31]; P < .001 for quadratic trend; genetic risk score [GRS] of 1 vs reference score [GRS of 4]: HR, 1.10 [95% CI, 1.01-1.19; GRS of 6 vs reference score [GRS of 4]: HR, 1.09 [95% CI, 1.00-1.18]; P = .03 for quadratic trend). Significant interactions were also found between actual age at menarche and genetically determined age at menarche with all-cause mortality (HR of mortality associated with age of menarche <12 year was 1.24 [95% CI, 1.10-1.40] in the GRS of 1 group and 1.44 [95% CI, 1.21-1.72] in the GRS of 6 group; P = .001 for interaction). Women with mismatch of actual age and genetically determined age at menarche had the highest mortality risks; participants with the lowest genetic risk score and the highest age at menarche had an HR of 2.12 (95% CI, 1.58-2.83), and participants with the highest GRS and the lowest age at menarche had an HR of 1.44 (95% CI, 1.21-1.72). Conclusions and Relevance The results suggest that both actual age and genetically determined age at menarche exhibit U-shaped associations with all-cause mortality. Women with mismatch of actual age and genetically determined age at menarche may have the highest risk of all-cause mortality.