Unfavourable glucose metabolism is associated with functional somatic disorders. A cross-sectional general population-based study: The DanFunD study

Objectives: Several studies have observed associations between unfavorable levels of blood glucose metabolic markers (i.e., fasting glucose, fasting insulin, glycated hemoglobin (HbA1c), and insulin resistance (HOMA-IR)) and functional somatic disorder (FSD). However, such associations have not yet been systematically analyzed in a general population-based sample using various FSD delimitations simultaneously. The aim of this study was to assess whether an unfavorable glucose metabolism is associated with FSD.

Design: Cross-sectional population-based study SETTING: Ten municipalities in the western part of greater Copenhagen area in Denmark PARTICIPANTS: A total of 8183 men and women aged 18-76 years were included. Various delimitations of FSD, i.e., chronic fatigue (CF), chronic widespread pain (CWP), irritable bowel (IB), and bodily distress syndrome (BDS), were measured using validated self-administrated questionnaires. In a stratified subsample, BDS was also assessed by diagnostic interviews.

Outcome measures: Logistic regression models were estimated for each delimitation of FSD as outcome and fasting glucose, fasting insulin, HbA1c, and estimated insulin resistance. Results were adjusted for age, sex (model 1), lifestyle, and social factors (model 2) and presented as odds ratios (OR) with 95 % confidence intervals (CI).

Results: When only adjusting for sex and age, positive associations were found between all FSD delimitations and glucose, insulin, and HbA1c, except for between IB and HbA1c. Positive associations were also found between all questionnaire-based BDS groups, and men with BDS confirmed by diagnostic interviews and elevated insulin resistance. After adjusting for lifestyle and social factors, associations remained significant between both CF and glucose and HbA1c and between multi-organ BDS and glucose and HbA1c. Further, CF, single-organ BDS, multi-organ BDS, and women with overall-BDS also remained associated with increased levels of insulin resistance.

Conclusion: FSD seems to be associated with especially an increase in plasma insulin levels and increased levels of insulin resistance. Elevated levels of blood glucose and HbA1c among all FSD groups could also completely be explained by unhealthy lifestyle. Prospective studies are needed for further clarification of the clinical relevance of this observation.