Is quality of life impairment associated with chronic diseases dependent on educational level?

Previous research indicates that quality of life impairment as a result of chronic diseases differs between socioeconomic groups, but the pattern seems to vary between health-related quality of life (HRQOL) outcomes. We tested for a one-item and a multi-item outcome whether associations between diseases and HRQOL varied between educational levels. Data come from Dutch participants of HELIUS (N =4615, aged 18-70). Education was defined as low, middle or high. Myocardial infarction, angina pectoris, hypertension, diabetes, obesity and depressed mood were measured using physical examination and/or self-report. Outcomes were fair/poor self-rated health (SRH) and physical (PCS) and mental (MCS) SF-12 scores. Interaction terms and relative excess risk due to interaction (RERI) were used as measures of additive interaction. SRH and PCS were worst in lower educated participants, whereas MCS was worst in middle educated participants. Out of thirty-six interactions tested, four were statistically significant, with risks of poor HRQOL being both larger and smaller in low vs. high education groups. Obesity was associated with smaller risk of fair/poor SRH in low vs. high educated [RERI=-2.49 (-4.66; -0.33)]. Depressed mood was associated with more [b=-3.34 (-6.14; -0.54)] and hypertension with less reduction in PCS [b=1.23 (0.18; 2.27)] in middle vs. high educated. Depressed mood was highly associated with MCS, but less so in middle vs. high educated [b=4.09 (0.72; 7.47)]. Despite a higher prevalence of diseases in low education groups, if measured in absolute terms, most diseases were not associated with larger impairment of HRQOL in lower vs. higher educated groups, regardless of the outcome measure used