Fisher-Rao distance and sex differences in disease prevalence trajectories

ObjectivesWe introduce a new application of the Fisher-Rao geodesic distance to quantify sex differences in age-stratified chronic-disease prevalence trajectories, modelling those trajectories as dynami-cal systems on the hyperbolic plane and using GBD 2021 data. MethodsWe analysed prevalence for 10 major chronic conditions across three regions--US states (50 states + DC), 24 Western European countries, and 47 Japanese prefectures--over 1990-2019. We logit-transformed prevalence and summarised each age-sex cohort by normal-approximation parameters ({micro}, {sigma}), which were then embedded in the hyperbolic plane. Sex differences were quantified as the difference between the total Fisher-Rao trajectory lengths for males and females. We assessed cross-regional consistency using parametric (mean differences) and nonparametric (Cohens g) summaries, and compared Fisher-Rao results to KL divergence, absolute mean differences, and absolute SD differences. Study designCross-sectional analysis of GBD 2021 prevalence data modelled as trajectories in the hyperbolic plane. ResultsThe Fisher-Rao distance showed greater cross-regional consistency than the alternative metrics. Males showed greater trajectory shifts in neoplasms, cardiovascular diseases, chronic respiratory diseases, diabetes/kidney diseases, skin/subcutaneous diseases, and sense organ diseases. Females showed greater shifts in neurological disorders, mental disorders, and substance use disorders. Digestive diseases exhibited mixed patterns. ConclusionsThis geometry-informed metric outperforms alternatives in assessing sex disparities in disease burdens, enhancing public health surveillance and equity in chronic disease management. Future extensions should incorporate gender dimensions.