Decomposition of Disability Prevalences. Age and Rate Effects in Northern Sweden, 1900–1950

This study examines changes in disability prevalence during Sweden's demographic transition, focusing on the relative contributions of population aging and changing disability rates. Using unique longitudinal data from parish registers covering 194,500 individuals in Västerbotten county 1900–1950, we analyze trends in four disability categories: sensory, physical, mental and intellectual disabilities. Through demographic decomposition methods, we separate the effects of changes in population age structure from changes in age-specific disability rates. Our findings reveal that the substantial increase in disability prevalence was primarily driven by changes in disability rates during the period studied rather than population aging. Mental disabilities showed the most pronounced increase, rising from 0.8% to 2.5%, while other disability types remained stable or declined. The impact was particularly strong among middle-aged adults (25–54 years), challenging assumptions about the predominant role of population aging in historical disability trends. Our results suggest that social and environmental factors played a more significant role than demographic change in shaping disability prevalence during times of demographic transition.