Effect of Cigarette Smoking on Disease Progression in Idiopathic Parkinson's Disease Patients

Abstract

"Introduction: Cigarette smoking is known to have a protective role against the development of idiopathic Parkinson’s disease (IPD). Despite this, there have been few studies focusing on whether cigarette smoking is able to slow IPD disease progression. The few that have examined this issue must be regarded with care due to their intrinsic methodological problems which have likely hampered their power to detect any potential neuroprotective effect of cigarette smoking. Given that a relatively small proportion of female IPD patients has a history of smoking it is reasonable to distinguish disease progression relative to gender, or simply to include only male patients, neither of which the previous studies did. We therefore evaluated the neuroprotective role of cigarette smoking in male IPD patients. Method: A total of 81 male IPD patients, who regularly visited Ajou University hospital neurologic clinic, were enrolled in this study. All patients were evaluated by means of a structured questionnaire. General demographic data and Unified Parkinson’s Disease Rating Scale (UPDRS) results were compared for each group in order to determine the effects of smoking on IPD progression. Results: Among 81 patients, 25 patients (smoker group) were current smokers or stopped smoking only after the IPD symptomatic onset. The remaining 56 patients (non-smoker group) were those who had ceased smoking prior to the onset of IPD symptoms or those who had never smoked. The age (62.7 yrs Vs. 68.2 yrs, p=0.072), disease duration (5.3 yrs Vs. 4.8 yrs, p=0.344), and levodopa dosage (616.8 mg Vs. 572.9 mg, p=0.583) were similar between the smoker group and non-smoker group. However, the age of IPD onset (57.3 yrs Vs. 63.5 yrs, p=0.047), UPDRS motor scores (14.8 Vs. 19.1, p=0.034), particularly the akineto-rigid subscores (7.1 point Vs. 9.7 point, p=0.022), and the UPDRS motor score progression rates were lower in the smoker group than those in the non-smoker group (3.4 points /year Vs. 5.3 points /year, p=0.007). In a Cox regression analysis, the age of IPD onset was the most significant prognostic factor. When 25 patients from the smoker group were matched to the age of IPD onset and onset phenotype matched controls for 25 patients from the non-smoker group, the smoker group still had a lower UPDRS motor score (14.8 points Vs. 20.3 points, p=0.032), and a lower UPDRS motor score progression rate than the non-smoker group (3.4 points per year Vs. 5.1 points per year, p=0.037). Conclusion: This study demonstrated that the continuation of cigarette smoking has a protective effect in male IPD, effectively slowing the rate of disease progression. Even after adjusting for the age of IPD onset, smoking was still identified as being able to significantly slow the progression of IPD. "