Comparison of age of onset and development of motor complications between smokers and non-smokers in Parkinson's disease.
BACKGROUND
There is growing evidence from case-control and from cohort studies that smoking is inversely related to the risk of developing Parkinson's disease (PD). However, it is still controversial if PD starts at an older age in ever-smoking patients compared to never-smoking ones.


METHODS
The present retrospective study compares in a large series of 512 out-patients, collected over the last 24 years, the age of onset of the complaints, the age at which PD was diagnosed and the start of levodopa treatment between ever- and never-smokers. Also, the occurrence of long-term side-effects of the drug was evaluated. 184 PD patients with a history of smoking were compared with 328 who had never smoked. The subgroups with and without a family history of PD were analysed separately.


RESULTS
In the overall ever-smoking group, as well as in the subgroup without a family history, the onset of the disease and the time of the diagnosis of PD and the time at which levodopa was started occurred at an older age than in the never-smoking group. This difference could not be demonstrated in the patients with a family history, due to the low number of cases and the lack of statistical power. Although the follow-up period was the same in both study groups, motor fluctuations and dyskinesia were more frequent and appeared earlier after levodopa treatment in the non-smoking compared to the ever-smoking PD patients. Only for cognitive impairment there was a non-significant trend in the smoking group.


CONCLUSIONS
The present study confirms the protective action of smoking on PD and also suggests some modulating effect of smoking on the dopaminergic system.
De Reuck
J
J
Department of Neurology, University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. jacques.dereuck@yucom.be
De Weweire
M
M
Van Maele
G
G
Santens
P
P
D017668:Age of Onset; D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000188:drug therapy / Q000503:physiopathology; D015331:Cohort Studies; D004409:Dyskinesia, Drug-Induced / Q000503:physiopathology; D005260:Female; D006803:Human Development; D006801:Humans; D007980:Levodopa / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology*; D010300:Parkinson Disease / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology*; D012907:Smoking / Q000009:adverse effects; D013997:Time Factors
D000978:Antiparkinson Agents; D007980:Levodopa