Plasma vitamin D and cytokines in relation to exercise in patients with fibromyalgia- A 15-week strength training intervention trial

The underlying causes of fibromyalgia are not fully understood and a link to chronic inflammation and vitamin D deficiency has been suggested. The mechanisms involved in the associations of fibromyalgia to vitamin D, biomarkers of inflammation and their relation to exercise have not been reported previously. This study aimed to investigate the effects of exercise on plasma 25-hydroxyvitamin D3 levels in patients with fibromyalgia, and further to examine the associations between biomarkers of chronic inflammation and vitamin D status.

This is a sub-study of a larger randomised controlled multi-center trial. Women with fibromyalgia (n=84) aged 20-65 years and 36 age-matched healthy controls were included. The fibromyalgia patients were randomised to resistance exercise or relaxation therapy and were examined based on physical capacity, symptoms and biomarkers including plasma 25-hydroxyvitamin D3 and cytokines.

At baseline, participants with fibromyalgia had lower plasma 25-hydroxyvitamin D3 compared to controls, 78.0 vs. 90.6 n mol/l (p=0.041). The 25-hydroxyvitamin D3 in participants with fibromyalgia increased after the intervention (p<0.001), but not in the controls. Multivariate data analyses showed an association between several cytokines and 25-hydroxyvitamin D3 in fibromyalgia at baseline, but not after the intervention. There were subgroups of patients who responded differently to exercise.

In women with fibromyalgia, several cytokines and 25-hydroxyvitamin D3 were associated. The vitamin D levels increased after resistance exercise and relaxation therapy. Different subgroups responded differently to strength training also from the point of objective data such as vitamin D and cytokines, which emphasise individual therapy strategies for patients with fibromyalgia.