Comorbidity and health-related quality of life among Australian adults with psychological distress: a detailed longitudinal study

Abstract Aim This observational study explores how clinically relevant comorbidities affect health-related quality of life (HRQoL) in individuals with psychological distress (PD), focusing on the number, types, and patterns of comorbidities to improve patient care and outcomes. Subject and methods We utilized unit record data for individuals with PD from the Household, Income, and Labor Dynamics in Australia (HILDA) survey. HRQoL, expressed as the health state utility score (HSU), was assessed via the Short-Form Six-Dimension (SF-6D) health survey derived from the 36-Item Short Form Survey (SF-36) and calculated using an Australian scoring algorithm. Multimorbidity was defined as the presence of two or more chronic conditions. A linear mixed model (LMM) was used to assess the impact of comorbidities on HRQoL in individuals with PD, and additional LMM regressions were performed to examine differences based on comorbidity type and pattern. Results The final sample included 26,991 observations (mean age 40.75 years; 58.25% female). Among individuals with PD, 31.36% had at least one comorbidity, with cardiovascular disease the most common (14.09%). The most prevalent pattern was ‘cardiovascular + musculoskeletal’ (9.43%). Higher numbers of comorbidities significantly worsened HRQoL, from −0.01 (95% CI −0.03, 0.01) for one comorbidity to −0.06 (95% CI −0.08, −0.03) for five comorbidities. Cancer had the greatest impact (−0.02; 95% CI −0.03, −0.02), while patterns involving cardiovascular and cancer or metabolic with multiple conditions reduced HSU by −0.03 (95% CI −0.05, −0.01) to −0.05 (95% CI −0.08, −0.02). Conclusions The types and patterns of comorbidities significantly impact HRQoL, even with a consistent comorbidity count. Early detection and treatment of these conditions can enhance HRQoL in individuals with PD.