Sex differences in frailty trajectories among older adults in Mexico: a 17-year longitudinal cohort study

Introduction Frailty is an ageing-related state associated with disability and mortality. Women often experience higher frailty but lower mortality than men, a pattern described as the male-female health-survival paradox. Evidence from low- and middle-income settings is limited. We examined sex differences in frailty trajectories and terminal decline in Mexico. Methods We analysed five waves (2001-2018) of the nationally representative Mexican Health and Aging Study (MHAS) including 12,440 adults ([≥]50 years at baseline). Frailty was measured using a 31-deficit frailty index (FI score; 0-1). We used survey-weighted linear mixed-effects models with time interactions, adjusted for sociodemographic, behavioural and health covariates to model sex differences in frailty trajectories. Terminal decline in FI was modelled among those who died using mixed-effects models on the time-to-death scale. Results A total of 12,440 adults aged 50 to 105 years were included, with a mean age of 62.1 years (SD 9.6); 5,698 men (45.8%) and 6,742 women (54.2%). Mean baseline FI was 0.17 (SD 0.12), higher in women than men (0.19 vs 0.16; P<0.001). After adjusting, women had a 0.014 higher mean FI than men at baseline (adjusted mean difference; 95%CI 0.008, 0.020), with difference widening over follow-up, increasing from 0.016 at 2 years to 0.029 at 17 years. Analysis of terminal decline found that accumulation of frailty accelerated in the years preceding death; with results suggesting that women reached death with higher frailty than men (difference 0.029; 95%CI 0.009, 0.048). Conclusion Women experienced higher and more rapidly increasing frailty compared to men and carried a greater frailty burden in the years preceding death. These findings underscore the importance of considering sex differences in frailty trajectories when developing healthy ageing strategies that address the life-course vulnerabilities disproportionately driving frailty accumulation in women in low- and middle-income countries.