Insulin, Glucose and Lipid Biomarkers as Possible Risk Factors for Functional Somatic Disorder: A Five-Year Follow-Up of the DanFunD Cohort.

Background: Functional somatic disorder (FSD) is prevalent, but pathological pathways have not yet been identified. Cross-sectional studies suggest an association between FSD and lipid and glucose metabolism. The aim of the present prospective study was to assess whether metabolic factors represent possible risk factors for development of FSD. Methods: A population-based cohort of 9656 men and women aged 18-76 years was established in 2011-2015, and 5738 participated in a re-examination after a median of 65 months. At both baseline and follow-up, participants answered questionnaires on lifestyle and various delimitations of FSD including bodily distress syndrome (BDS), chronic fatigue (CF), chronic widespread pain (CWP), irritable bowel (IB), and multiple chemical sensitivity (MCS). Fasting values of cholesterol, triglycerides, glucose, HbA1c, insulin, and insulin resistance were assessed at baseline and analyzed in relation to incidence of FSD using logistic regression models, adjusted for age, sex, lipid- and glucose-lowering medications, obesity, social status, lifestyle, and sleep quality. Results: Several small, although significant, effects were observed. Lower levels of cholesterol were associated with development of BDS (OR: 0.982 (95% CI: 0.971-0.993)), CF (OR: 0.980 (95% CI: 0.964-0.996)), and CWP without co-morbid FSS among men. Higher levels of triglycerides were associated with development of CF (OR: 1.022 (95% CI: 1.003-1.041)). Glucose and HbA1c levels were not associated with development of FSD. Insulin and HOMA-IR levels were associated with development of CF in a non-linear relation, being negative at lower levels and changing to a positive relation at higher levels. Conclusions: More large-scale cohort studies are necessary to explore whether metabolism could play a role in the pathological pathway of FSD as indicated in the present study.