Life-Stage Differences in the Longitudinal Associations of Multimorbidity Profiles with Economic Burden, Health-Related Quality of Life, and Inpatient Utilization

Background/Objectives: Multimorbidity is associated with substantial healthcare burdens, but its associations with health and economic outcomes among young adults remain poorly characterized. This study examined associations between clinically defined multimorbidity profiles and expenditures, catastrophic healthcare expenditure, health-related quality of life, and inpatient utilization across adult life stages. Methods: Medical Expenditure Panel Survey Panel 24 data were analyzed for 4331 U.S. adults followed from 2019 through 2022, including 942 young adults. Respondents were classified into five profiles: no included conditions, respiratory only, cardiometabolic only, any-cancer involved, and cardiorespiratory. Longitudinally weighted generalized estimating equations were fitted. Results: Profile distribution differed significantly across age groups. Among young adults, overall profile and profile-by-year tests were nonsignificant for total expenditures and most other outcomes. In 2019, the cardiorespiratory profile was associated with higher expected expenditures than no included conditions (expenditure ratio = 3.44, 95% CI: 1.59–7.46; p = 0.002). It was also associated with higher hospitalization odds across 2019–2022 (OR = 3.39, 95% CI: 1.28–8.99; p = 0.014), although the overall profile test was nonsignificant. Sex, insurance, and income were associated with several outcomes. Mental health scores were lower in 2021 and 2022 than in 2019 within the reference profile, without evidence of uniform changes across profiles. Conclusions: Overall profile effects were not consistently demonstrated among young adults. Parameter-specific cardiorespiratory estimates suggested a potentially elevated burden but remained exploratory because of sparse observations and nonsignificant overall tests. Socioeconomic vulnerability remained an important correlate of healthcare burden.