Burden and temporal trends of major depressive disorder in older adults: a 10-year population-based longitudinal study on interlinked region-wide health registries, 2013-2023.

AIMS: Population-based longitudinal evidence using administrative healthcare registries remains limited. We aimed to estimate the burden and temporal trends of major depressive disorder (MDD) among individuals aged ≥65 in Lombardy, Italy, 2013 to 2023. METHODS: We conducted a retrospective population-based longitudinal study using multi-source administrative healthcare registries (Lombardy region, Italy), including an open cohort of individuals aged ≥65 years. Incident and prevalent MDD cases were identified from 2013 to 2023, through an algorithm combining hospital discharge records, administrative exemptions, long-term care facility admissions and community psychiatric services. Age-standardised incidence rates per 100,000 person-years and annual prevalence (%) were estimated overall, by sex and age, using the age-truncated (≥65) WHO standard population. Annual percent changes (APCs) and 95% confidence intervals (CIs) were estimated by Poisson regressions. RESULTS: We identified 19,851 incident MDD cases during the study period. Age-standardised incidence declined from 126.5/100,000 person-years (95% CI 121.7-131.3) in 2013 to 50.6 (47.6-53.7) in 2023, with an APC of 10.8% (-11.8 to -9.7). Age-standardised annual prevalence decreased from 0.94% (0.93-0.95) in 2013 to 0.63% (0.62-0.64) in 2023, corresponding to an annual decline of 3.0% (-4.7 to -1.3). Rates were higher among females. Burden and trends did not differ significantly by sex but across age groups, with the largest reductions among individuals aged 80 years or older. CONCLUSIONS: Administrative data capture clinically diagnosed MDD within the healthcare system, rather than the broader burden in the community. Comparable epidemiological estimates are needed to interpret trends across different settings.