Willis et al. write [1]:

"Cross sectional study of 3,459,986 disabled Americans, aged 30-54, who were receiving Medicare benefits in the year 2005. ... We identified 14,354 Medicare beneficiaries with YOPD (prevalence = 414.9 per 100,000 disabled Americans). White men comprised the majority of cases (48.9%), followed by White women (34.7%), Black men (6.8%), Black women (5.0%), Hispanic men (2.4%), and Hispanic women (1.2%). Asian men (0.6%) and Asian women (0.4%) were the least common race-sex pairs with a YOPD diagnosis in this population (chi square, p < 0.001). Compared to the general population of medically disabled Americans, those with YOPD were more likely to receive medical care for depression (OR: 1.89, 1.83-1.95), dementia (OR: 7.73, 7.38-8.09), substance abuse/dependence (OR: 3.00, 2.99-3.01), and were more likely to be hospitalized for psychosis (OR: 3.36, 3.19-3.53), personality/impulse control disorders (OR: 4.56, 3.28-6.34), and psychosocial dysfunction (OR: 3.85, 2.89-5.14)."

Reference

[1] Parkinsonism Relat Disord. 2013 Feb;19(2):202-6.
"Epidemiology and neuropsychiatric manifestations of Young Onset Parkinson's Disease in the United States."
Willis AW1, Schootman M, Kung N, Racette BA.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3562561/

John