Fatigue and excessive daytime sleepiness in idiopathic Parkinson's disease differently correlate with motor symptoms, depression and dopaminergic treatment

Background and purpose: A comprehensive study of both fatigue and excessive daytime sleepiness (EDS) in association with Parkinson’s disease (PD)‐related symptoms and treatment has not been performed yet. To assess the frequency and severity of fatigue and EDS in patients with idiopathic PD and to study their relation to motor and non‐motor symptoms and dopaminergic treatment. Methods: We prospectively assessed Fatigue Severity Scale (FSS) scores, Epworth Sleepiness Scale (ESS) scores, Beck Depression Inventory (BDI) scores, severity (Unified PD Rating Scale, UPDRS, part III; Hoehn & Yahr staging) and duration of the disease, and the current dopaminergic treatment in 88 consecutive patients with idiopathic PD. Results: Fatigue was found in 52 (59%), EDS in 42 (48%), and both complaints in 31 (35%) patients. Fatigued patients had higher UPDRS III scores (23.5 ± 11.1 vs. 18.6 ± 7.6, P = 0.03), higher Hoehn & Yahr staging (2.4 ± 0.9 vs. 2.1 ± 0.7, P = 0.03), and higher BDI scores (13.4 ± 7.1 vs. 9.1 ± 5.8, P = 0.004) than non‐fatigued patients. In contrast, UPDRS III, Hoehn & Yahr, and BDI scores did not differ between patients with or without EDS. However, the type of dopaminergic treatment (levodopa monotherapy versus combination of levodopa/dopamine agonists) was associated with significant differences in ESS (8.5 ± 5.2 vs. 10.8 ± 4.3, P = 0.04), but not FSS scores (4.1 ± 1.5 vs. 4.3 ± 1.5, P = 0.55). Disease duration correlated with ESS scores (r = 0.32, P = 0.003), but not with FSS scores (r = −0.02, P = 0.82). Conclusions: In PD, there is a significant overlap of fatigue and EDS, but the two symptoms are differently correlated with the severity of motor symptoms, disease duration, depression, and dopaminergic treatment.