Risk of Parkinson's disease among first-degree relatives: A community-based study.
OBJECTIVE
To determine the relative risk (RR) and cumulative incidence of idiopathic Parkinson's disease (PD) in first-degree relatives of PD patients compared with relatives of controls from the same geographic region.


METHODS
A family history questionnaire was used to obtain information on all first-degree relatives of cases and controls. A subset of these first-degree relative was also examined. A Cox proportional hazards model with double-censoring techniques for missing information was used to model the RR for PD, adjusting for gender, ethnicity, and relationship to proband.


RESULTS
A total of 1,458 first-degree relatives of 233 PD patients were 2.3 times as likely (95% CI = 1.3 to 4.0) as 7,834 relatives of 1,172 controls to develop PD. The cumulative incidence of PD to age 75 among first-degree relatives of PD patients was 2% compared with 1% among first-degree relatives of controls. The risk in male first-degree relatives was higher than in female relatives (RR = 2.0, 95% CI = 1.1 to 3.4) and the risk in relatives of Caucasians was higher than in African-Americans and Hispanics (RR = 2.4, 95% CI = 1.4 to 4.1). Risk for siblings and parents of probands was similar.


CONCLUSIONS
Susceptibility to PD is increased in first-degree relatives of both sporadic and familial cases. The pattern of inheritance and the relationship between genetic and environmental risk factors warrant further study.
Marder
K
K
Gertrude H. Sergievsky Center, College of Physicians and Surgeons, New York, New York, USA.
Tang
M X
MX
Mejia
H
H
Alfaro
B
B
Côté
L
L
Louis
E
E
Groves
J
J
Mayeux
R
R
D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000235:genetics*; D012307:Risk Factors; D011795:Surveys and Questionnaires