Lifestyle factors as predictors of incident functional somatic disorder. Five-year follow-up of The DanFunD study.

Aims: To assess whether lifestyle factors, including sleep pattern, are predictors for the development of functional somatic disorder (FSD).

Methods: A population-based prospective cohort of 9656 men and women aged 18-76 years was established in 2011-2015 and invited for re-examination in 2017-2020, when 5738 participated. Median follow-up period was 65 months. Participants filled in validated questionnaires on lifestyle, sleep pattern and various delimitations of FSD, which were operationalized using two different approaches: bodily distress syndrome (BDS) and functional somatic syndromes (FSS) (i.e. chronic fatigue, chronic widespread pain (CWP), irritable bowel, and multiple chemical sensitivity (MCS)). Baseline lifestyle and sleep pattern in relation to incidence of BDS and FSS (chronic fatigue, CWP, irritable bowel, MCS) was analysed by logistic regressions, adjusted for age, sex and subjective social status.

Results: Inferior sleep quality at baseline predicted both incidence of BDS and all FSS delimitations except MCS. Smoking, alcohol intake, and low physical activity, but not diet, were predictors for the development of BDS. No uniform pattern was observed for the FSS. Smoking predicted development of chronic fatigue, CWP and irritable bowel, but not MCS. Alcohol and food quality only influenced the development of chronic fatigue whereas low physical activity only influenced the development of chronic fatigue and CWP.

Conclusions: Lifestyle factors and sleep pattern seem to be predictors for some delimitations of FSD, but the importance of the various lifestyle factors is different for the different delimitations. The study shows the importance of analysing the various FSSs separately.