Stress levels predict substantial improvement in pain intensity after 10 to 12 years in women with fibromyalgia and chronic widespread pain: a cohort study

BACKGROUND: Previous studies of prognosis for women with Fibromyalgia (FM) or chronic widespread pain (CWP) show contradictory results. However, some women appear to improve in pain and other core symptoms over time. There is limited knowledge about predictors of substantial improvement in pain intensity over a longer period of time. The primary objective of this study was to investigate the natural course of pain intensity and distribution of pain over 10 to 12 years in a cohort of 166 women with FM or CWP. Secondarily we wanted to investigate predictors of substantial improvement (≥50%) in pain intensity after 10 to 12 years. METHODS: The study is a longitudinal prospective cohort study. 166 women with FM or CWP were followed up after 10 to 12 years. 126 women (76%) participated in the follow-up and completed a battery of questionnaires concerning pain intensity, pain distribution and other physical and mental aspects of health. Differences in symptoms within the cohort over 10 to 12 years and predictors of substantial improvement (≥50%) in pain intensity were calculated. RESULTS: Pain had improved at the 10 to 12 year follow-up (p < 0.001) with a mean change of − 9.2 mm (SD 23.3, 95% CI: − 13.3; − 5.0) for pain intensity and − 2.0 sites (SD 4.2, 95% CI: − 2.7; − 1.2) for pain distribution. Nine percent of the 126 women showed an individual moderate improvement in pain intensity while 16% showed a substantial improvement at the follow-up as compared to baseline. Lower symptoms of stress and higher pain intensity at baseline predicted higher probability of reporting at least 50% less pain intensity after 10 to 12 years as compared to baseline. CONCLUSIONS: A majority of women with FM and CWP appear to have a positive course of pain over time, which should be communicated to these patients in health care. Reducing stress levels might contribute to better chances of improvement over time. TRIAL REGISTRATION: Clinicaltrials.gov NCT02872129, registered 06/30/2016.