Family-based case-control study of cigarette smoking and Parkinson disease.
OBJECTIVE
To determine whether people with Parkinson disease (PD) are less likely to report a history of cigarette smoking than their unaffected siblings.


BACKGROUND
Previous studies reported that individuals with PD are half as likely to have smoked as those unaffected by PD. Other studies reported that smoking modified the risk of PD due to polymorphisms in the MAO-B and nNOS genes. Thus, genetic studies of PD should consider confounding or interaction with smoking history as well. The authors have collected detailed smoking histories on a family-based case-control sample ascertained for genetic studies of PD.


METHODS
In a matched case-control study of 140 sibships, individuals with PD (n = 143) were compared to sibling controls (n = 168). Cigarette smoking history was collected by a structured telephone interview. Conditional logistic regression was used to examine the relationship between smoking and PD while controlling for confounding by age and sex.


RESULTS
Ever smoking, current smoking, and increasing duration (in years), dose (in packs/day), and intensity (in pack-years) of smoking were significantly inversely associated with PD (p < 0.05). The association was not modified by sex, age at onset, or recency of exposure.


CONCLUSIONS
Consistent with previous studies, individuals with Parkinson disease are significantly less likely to have smoked regularly than their unaffected siblings. This association was detected even though discordant sibling pairs are more likely to be overmatched for environmental exposures than unmatched case and control groups.
Scott
W K
WK
Department of Medicine and Duke Center for Human Genetics, Duke University Medical Center, Box 3445, Durham, NC 27710, USA. bill.scott@duke.edu
Zhang
F
F
Stajich
J M
JM
Scott
B L
BL
Stacy
M A
MA
Vance
J M
JM
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D004777:Environment; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000453:epidemiology* / Q000235:genetics; D012307:Risk Factors; D035781:Siblings; D012907:Smoking / Q000453:epidemiology* / Q000235:genetics; D016540:Smoking Cessation