Epidemiology of early-onset Parkinson disease (EOPD) worldwide: East versus west.

Parkinson disease (PD) is characterized by the presence of bradykinesia with either rest tremor, muscle rigidity, or postural instability. If the features for PD are present but the age at onset (AAO) is before the usual but later than 21 years of age, it is considered as early-onset PD (EOPD). With Eastern countries projected to account for over 60 % of the world's population, it is paramount to understand the differences in EOPD between Western and Eastern countries. Epidemiology can differ substantially between the East and West, such as China showing a much steeper rise in EOPD prevalence and incidence with age, or Japan and Korea showing a female predominance in EOPD for certain age groups. Symptomatology appears to be similar across Western and Eastern populations, though some Eastern populations may have a higher prevalence of the akinetic-rigid or postural instability/gait difficulty motor phenotypes. Genetic epidemiology, conversely, varies significantly between the East and West, though some genes are frequently implicated in both (such as LRRK2, PINK1, PRKN, and GBA). Next, treatment patterns also exhibit substantial geographical variation, which could be driven by local availability of medications, adequacy of staff training and infrastructure, and local regulatory bodies. Lastly, regardless of region, EOPD exerts a profound psychosocial impact on patients, such as strained relationships, unemployment, and psychological distress. In summary, understanding these differences (and similarities) between the East and West could help generate innovative solutions, while the development of healthy habits and robust social networks should also be actively encouraged in all patients.