Background

Parkinson’s disease Parkinson’s disease (PD) is a degenerative movement disorder affecting 1 % to 2 % of the population over 60 years of age [1]. In one study on incidence rates, re-searchers reported that 0.5 % of patients were diagnosed before the age of 40 years, 3.5 % before the age of 50 years and more than 60 % between the ages of 65 and 79 years [2]. The core motor features of PD comprise com-binations of bradykinesia, resting tremor, rigidity, flexed posture, ‘freezing ’ and loss of postural reflexes [3]. PD is a disabling condition with significant impact on quality of life (QoL) [4]. Notably, nonmotor symptoms of PD, such as dementia, sleep disturbances, depression and falls, may also have a significant negative impact on QoL [5]. Comorbidity is common in PD. Longitudina