Autonomic arousal and heart rate variability in functional somatic disorder - a cross-sectional population-based study

OBJECTIVE: The bodily distress syndrome (BDS) checklist has proven to be useful diagnostic aid and as screening tool for functional somatic disorder (FSD). It has been hypotheses that the symptoms clusters of the checklist represent autonomic activity. This study aims to investigate associations between autonomic activity (Heart rate variability, HRV) and somatic symptoms profiles measured by the BDS checklist and diagnoses of FSD based on interviews.

METHODS: This cross-sectional population-based study included 6891 men and women aged 18-72 years. Somatic symptom profiles were measured by the 25-item BDS checklist, and five short-term HRV measures (MeanRR, RMSSD, LF, HF, and LF/HF) were obtained. In a stratified subsample (n = 1590), diagnoses of FSD was established by diagnostic interviews, performed by trained family physicians. Associations were tested with regression models. Measures of associations were mean difference with 95 % confidence intervals (CIs) for Mean RR and median ratio and 95 % CI for RMSS, LF, HF, and LF/HF.

RESULTS: Overall, higher BDS checklist scores were associated with lower HRV, particularly reduced mean RR intervals (-0.86, 95 % CI: -0,24;-0,49 for the total sum score). The strongest associations were seen for the cardiopulmonary symptom cluster (-3.58, 95 % CI: -0,05;-2.10). Clinically diagnosed FSD cases also showed lower mean RR compared to non-cases (-23.12, 95 % CI: -41.17;-5.07), especially the multi-organ type (-39.44, 95 % CI: -75.49;-3.39).

CONCLUSIONS: The study indicate that the symptom clusters of the BDS checklist are associated with autonomic arousal as measured by HRV. Further that individuals with FSD, especially the multi-organ type, had an increased sympathetic neural and neurohormonal activity, suggesting this may be an important physiological mechanism in FSD.