Objective: To evaluate associations between health-related quality of life, HRQoL, and inflammatory biomarkers in a normal population, and investigate whether associations could be explained by the presence of disease, lifestyle and/or psychological factors.
Methods: A randomly selected sample of a middle-aged Swedish population (n=961; aged 45-70 years, 50% women) was investigated. Self-reported data on HRQoL (SF-36), presence of disease, lifestyle and psychological factors, and plasma levels of biomarkers of inflammation: C-reactive protein (CRP), CXCL8, interleukin (IL)-1β, 6, and 10, and matrix metalloproteinase-9, were analyzed using correlation and regression analyses.
Results: After adjustment for sex and age, significant negative associations were seen for all scales of the SF-36 to plasma levels of IL-6 and CRP (except the Mental Health scale for CRP), and to a lesser extent to MMP-9, while only a few significant associations were noted for the other biomarkers. Associations with IL-6 were attenuated but generally remained significant after full adjustment (for age, sex, presence of disease, lifestyle and psychological factors) in regression analyses, while associations with CRP for many scales became nonsignificant after control for lifestyle factors.
Conclusions: Poor HRQoL was related to low grade inflammation in a normal population. The results suggest a possible pathway for earlier observed effects of HRQoL on mortality risk and indicate that low HRQoL is a sign of increased biological vulnerability. The data further indicate that IL-6, CRP, and MMP-9 are more informative markers than CXCL8, IL-1β, and IL-10 for these relationships, but also that they may not convey exactly the same information.