Hormone Therapy and Biological Aging in Postmenopausal Women.

Importance: Menopause is associated with biological aging, and hormone therapy (HT) is associated with health outcomes in postmenopausal women. Objective: To evaluate the association between HT use and discrepancies between chronological and biological age in postmenopausal women as well as the potential modifying role of socioeconomic status (SES). Design, Setting, and Participants: This population-based, retrospective cohort study included postmenopausal women registered in the UK Biobank. A baseline survey on HT use and biological aging biomarkers was conducted from March 2006 to October 2010. Data analyses were conducted in December 2023. Exposures: Information regarding HT use, the age at starting HT, and HT duration was collected via a touchscreen questionnaire. SES was evaluated by education, family income, occupation, and the Townsend Deprivation Index. Main Outcomes and Measures: Biological aging discrepancy was evaluated using validated phenotypic age, which was calculated using chronological age and 9 biomarkers measured at baseline. All-cause and cause-specific mortality were also assessed. Results: Among the 117 763 postmenopausal women (mean [SD] age, 60.2 [5.4] years), 47 461 (40.3%) ever used HT. The mean phenotypic age was 52.1 (7.9) years. Ever use of HT was associated with a smaller biological aging discrepancy than never use of HT (β, -0.17 years; 95% CI, -0.23 to -0.10 years). This smaller aging discrepancy was more evident in those who started HT at age 55 years or older (β, -0.32 years; 95% CI, -0.48 to -0.15 years) and in those who used HT for 4 to 8 years (β, -0.25 years; 95% CI, -0.35 to -0.15 years). The association between HT and a smaller aging discrepancy was more evident in women with low SES, with a significant interaction observed for education (higher education: β, -0.08 years [95% CI, -0.17 to 0.01]; other education: β, -0.23 [95% CI, -0.32 to -0.14] years; P for interaction = .02). Phenotypic aging discrepancy mediated 12.7% (95% CI, 6.3% to 23.9%) of the association between HT and all-cause mortality and cause-specific mortality. Conclusions and Relevance: In this study, postmenopausal women with historical HT use were biologically younger than those not receiving HT, with a more evident association observed in those with low SES. The biological aging discrepancy mediated the association between HT and decreased mortality. Promoting HT in postmenopausal women could be important for healthy aging.