Multimorbidity and mortality trends in the COVID19 syndemic in Madagascar covering 180 diseases 2015 2024

Multimorbidity and mortality shape population health in Madagascar, where chronic and infectious diseases interact across regions. Using surveillance data covering 180 diseases across 22 regions from 2015 to 2024, we quantified geographic disparities, dominant contributors to disease burden, and shifts associated with the COVID-19 syndemic. Stroke was the leading cause of death, with regional case-fatality rates often exceeding 45% and reaching nearly 99% for cardiac arrest in some urban areas. Stroke also showed strong correlations with hypertension (r = 0.97) and diarrhea (r = 0.98), highlighting interconnected vulnerabilities. During the COVID-19 period, overall disease frequency increased by 6.12% on average, though responses varied widely across conditions. Post-lockdown, incidence declined substantially (MRD = -90.17%), and mortality decreased slightly (MRD = -3.93%), yet disparities persisted. Groups with cardiovascular and mental health disorders exhibited the greatest instability. These findings illustrate how interacting epidemics reshape population vulnerability and underscore the importance of integrated strategies to strengthen health-system resilience.