Mediators of the Association Between Severity of Noncommunicable Diseases and Subjective Health-Related Quality of Life.

Aim: Noncommunicable diseases (NCDs) represent one of the greatest global burdens of disease and disability, and there is evidence that mental disorders associated with NCDs may reduce quality of life (QOL). We investigated the factors mediating the association between the severity of NCDs and subjective health-related QOL in 173 patients with NCDs.

Methods: We hypothesized that mental health indicators and inflammatory cytokines mediate the association between physical disease severity and subjective health-related QOL. We conducted a structural equation model analysis and selected variables representing mental health and inflammatory cytokines using a multivariable regression analysis and factor analysis.

Results: The structural equation model showed that mental health indicators such as anxiety and positive emotions are potential mediators, and that proinflammatory cytokines such as interleukin-6 (IL6) and tumor necrosis factor-α (TNF-α) may reduce subjective health-related QOL by increasing anxiety and suppressing positive emotions, without being particularly related to physical disease severity. The findings also suggest that anti-inflammatory cytokines such as interleukin-10 (IL10) and adiponectin (ADPN) are activated as physical disease severity increases, and likely protect against physical disease by enhancing positive emotions, potentially increasing subjective health-related QOL and resilience.

Conclusion: Mental health mediates the association between physical disease and subjective health-related QOL, and between inflammatory cytokines and subjective health-related QOL. Anti-inflammatory cytokines are activated by physical disease severity and have a protective effect on mental health.