Are Younger Korean Adults Getting Sicker or Getting Treated? Decomposing the Growth in Treated Chronic Disease Prevalence into Disease Burden, Treatment Uptake, and Claims Capture, 2010–2024

Background/Objectives: The number of Korean adults treated for chronic diseases has grown fastest at ages 30–49, but whether this reflects more disease or more treatment is unclear. Methods: Sex- and age-specific prevalence and treatment rates from the Korea National Health and Nutrition Examination Survey (three-year waves, 2010–2024) were linked to claims-based counts of treated patients with hypertension, diabetes, and hypercholesterolaemia. Changes were decomposed into population, prevalence, treatment rate, and residual claims capture ratio using the logarithmic mean Divisia index with Monte Carlo intervals. Results: Among adults aged 30–49 years, treated patients rose by 19% for hypertension, 39% for diabetes, and 123% for hypercholesterolaemia despite a 12% population decline. Survey prevalence was flat for hypertension (13.1% to 13.5%) and diabetes (5.4% to 5.5%), whereas treatment rates rose from 29% to 49% and from 35% to 57%. Treatment uptake accounted for more than the entire net increase for hypertension and diabetes (95% intervals excluding zero), and prevalence for little; for hypercholesterolaemia, prevalence and treatment contributed similarly. At ages ≥ 50, population growth dominated for hypertension and diabetes. Results were robust to alternative specifications, including survey-only decomposition. Conclusions: Growth in younger adults under treatment is more consistent with increased detection and treatment uptake than with rising prevalence.