It is well known that multimorbidity negatively impacts health-related quality of life (HRQoL). However, how psychosocial factors moderate this relationship remains unclear. The present study investigated the moderating effects of personality traits on the relationship between multimorbidity and HRQoL.

Data were extracted from three waves (i.e., Waves 13, 17, and 21) of the Household, Income, and Labor Dynamics in Australia (HILDA) survey and a representative cohort of the adult (20+ years) population was followed. The outcomes were three dimensions of SF-36: mental health, physical functioning, and general health. The predictor was the degree of multimorbidity, which was measured by counting the number of self-reported health conditions. The moderator was personality traits measured by the Five-Factor Model (extraversion, emotional stability, agreeableness, openness to experience, and conscientiousness). Mixed-effects models were used to explore the relationship between multimorbidity and HRQoL.

Overall, the study cohort comprised 13,285 adults in 2013 who were followed up to 2021, for a total of N = 32,950 observations. There were slightly more (53.9%) females, and the mean (SD) age was 50.3 (16.8) years. Personality traits significantly moderated the relationship between multimorbidity and HRQoL. For instance, extraversion and emotional stability significantly moderated the relationship between multimorbidity and mental health. The moderation effect sizes were larger than established minimal clinically important difference (MCID) thresholds. For example, the impact of 3 health conditions on mental health was moderated from 66 (extraversion score of 4) to 77 (extraversion score of 7), a difference of almost twice the MCID threshold of 6 established for mental health.

The results showed that personality traits moderated the relationship between multimorbidity and HRQoL to the extent of potentially influencing clinical decisions. Understanding the influences of personality traits on HRQoL in the context of varying degrees of multimorbidity could enhance interventions for improving quality of life.