Progression of fatigue in Parkinson’s disease – a 9‐year follow‐up

Background and purpose Although highly disabling, the pathogenesis and evolution of fatigue in Parkinson’s disease (PD) is largely unknown, and no sufficiently documented treatment currently exists. The aim of the present study was to investigate the evolution of fatigue during the first 9 years after diagnosis. Methods This study is part of the Norwegian ParkWest collaboration, a prospective population‐based longitudinal cohort study. The present study comprised 191 newly diagnosed patients and 170 control participants. Fatigue was assessed by the Fatigue Severity Scale, with examinations at baseline and then every other year up to 9 years of follow‐up. Linear mixed models were applied to investigate possible variables associated with fatigue. Results It was found that there was a statistically significant increase in the proportion of PD patients with fatigue during the first 9 years after diagnosis. A large proportion of patients had a significant increase or decrease in fatigue score between consecutive visits. In addition, the relative risk of persistent fatigue and ever having fatigue was higher than for controls. There were statistically significant longitudinal associations between higher levels of fatigue and female gender, comorbidity at baseline, depressive symptoms, dependency in activities of daily living and better cognitive functioning. Lower levels of fatigue were associated with the use of dopamine agonists. Conclusion Fatigue is a common, severely limiting symptom in PD. This study demonstrates associations with other factors that could yield a better understanding of the symptom and thus possible treatment strategies, although further investigations are necessary to establish causal relationships.