Functional Somatic Syndromes: Skin Temperatures and Activity Measurements Under Ambulatory Conditions

Functional somatic syndromes are mostly associated with pain and emotional distress. As one marker for the autonomic stress response, the distal skin temperature decreases during psychological stress. In patients with functional somatic syndromes, the distal skin temperature under baseline conditions (without stress induction) is usually lower than in healthy subjects, which could be due to the sustained presence of pain-related stress in such patients. The aim of our study was to investigate whether patients with functional somatic syndromes show altered skin temperatures also under everyday life conditions. 14 patients with functional somatic syndromes and 14 matched healthy control subjects were investigated under ambulatory conditions over six consecutive days. During this time, distal and proximal skin temperatures were continuously recorded and sleep-wake cycles were monitored by actimetry and sleep-wake diaries. Unexpectedly, the patients showed higher distal skin temperatures than control subjects in the afternoon. The objective temperature data did not match the patients' subjective experience: ratings of thermal comfort did not vary between the two groups. Moreover, similar levels of daytime activity were recorded in the two samples, even though patients reported more tiredness and more body tension than controls. We interpret the observed dissociation between objective skin temperature measurements and subjective ratings of the bodily thermal comfort as support for the notion of an alexisomia account (reduced bodily awareness) for functional somatic syndromes. Moreover, findings indicate that subjective complaints of tiredness and tension do not necessarily result in physical avoidance behaviour.