Smoking and Parkinson's disease: A case-control study in the Greek population

OBJECTIVE Parkinson's disease (PD) is a progressive neurodegenerative brain disorder of unknown etiology. It usually affects middle aged individuals and its prevalence increases with advanced age. Smoking in relation to PD has been the subject of numerous epidemiological studies, conducted in various countries all over the world, some of which have shown a negative association between smoking and PD, while others failed to prove such a relationship. Differences in methodology and in the genetic background of the study populations have been proposed to explain the discrepancy in findings. The purpose of this case-control study was to investigate the association between smoking and PD in a Greek population sample. METHOD A specially designed questionnaire was administered to 201 patients with PD and 442 unselected healthy control subjects residing in Northern Greece. Questionnaire items were related to smoking habits, such as time of smoking initiation, duration of smoking and daily cigarette consumption. Non-smokers were also questioned about their reasons for non-smoking. RESULTS Smoking in general was not directly related to PD, but a dose-dependent inverse association was observed; a significantly higher daily cigarette consumption and duration of smoking, and consequently mean packet-years was recorded by the healthy control subjects. In patients with PD who were smokers, the age at onset of the disease was positively correlated to packet- years. CONCLUSIONS This study did not demonstrate a lower risk for PD development in smokers, but provided indirect evidence of a possible neuroprotective role of smoking, showing that PD was inversely related to the dose of cigarette smoking (packet-years). However, it cannot be claimed that a simple observational study, with a limited number of subjects, can lead to firm conclusions about the association between smoking and PD. Further, more extensive, epidemiological studies are needed in this field.