Drug-induced parkinsonism as a risk factor for Parkinson's disease: a historical cohort study in Olmsted County, Minnesota.
OBJECTIVE
To investigate whether subjects who experienced a reversible episode of drug-induced parkinsonism have an increased risk of subsequent Parkinson's disease.


METHODS
We undertook a historical cohort study based on the medical records-linkage system of the Rochester Epidemiology Project in Olmsted County, Minnesota.


METHODS
All subjects in whom drug-induced parkinsonism developed between 1955 and 1990 and was indexed in the medical records-linkage system were identified. In the 24 eligible subjects, follow-up for the subsequent development of Parkinson's disease consisted of a total of 192.7 person-years. The observed number of cases of Parkinson's disease was compared with the expected number of cases in an age- and sex-matched cohort from the general population.


RESULTS
In 2 of 24 subjects with drug-induced parkinsonism, Parkinson's disease later developed. A comparison with the expected number of cases in the general population (0.08) yielded a relative risk of 24.3 (95% confidence interval, 2.9 to 87.5; P = 0.006).


CONCLUSIONS
Our findings suggest that drug-induced parkinsonism is associated with an increased risk of Parkinson's disease. Clarification of the mechanisms of this association may have preventive implications.
Department of Neurology, Mayo Clinic Jacksonville, Florida 32224, USA.
D R
DR
Chabolla
D M
DM
Maraganore
J E
JE
Ahlskog
P C
PC
O'Brien
W A
WA
Rocca
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000209:etiology*; D010302:Parkinson Disease, Secondary / Q000139:chemically induced* / Q000150:complications*; D012306:Risk; D012307:Risk Factors