A case-control study on cigarette,alcohol, and coffee consumption preceding Parkinson's disease

OBJECTIVE: To investigate the association between cigarette smoking, alcohol drinking, coffee consumption and Parkinson's disease (PD). METHODS: We selected subjects affected by idiopathic PD, with a Mini-Mental State Examination of > or =24, and controls matched 1 to 1 with cases by age (+/- 2 years) and sex. Controls were randomly selected from the resident list of the same municipality of residence of the cases. We assessed cigarette smoking, alcohol drinking, and coffee consumption preceding the onset of PD or the corresponding time for controls using a structured questionnaire, which also evaluated the duration and dose of exposure. Using conditional logistic regression analysis, we calculated adjusted OR and 95% CI. RESULTS: We interviewed 150 PD patients and 150 matched controls. Cigarette smoking (ever vs. never smokers OR = 0.66, 95% CI = 0.41-1.05, p = 0.08) did not show a statistically significant association with PD. We observed an inverse association between alcohol drinking (ever vs. never OR = 0.61, 95% CI = 0.39-0.97, p = 0.037) and coffee consumption (ever vs. never OR = 0.16, 95% CI 0.05-0.46, p = 0.0001) and PD. These associations remained significant after adjustment for other covariates: OR for ever vs. never alcohol consumption was 0.62 (95% CI = 0.43-0.89, p = 0.009) and that for coffee drinking 0.19 (95% CI = 0.07-0.52, p = 0.001). Heavy coffee consumption confirmed the inverse association between coffee and PD (more than 81 cup/year vs. none: OR = 0.20, 95% CI = 0.08-0.47, p < or = 0.0001). CONCLUSIONS: Consistent with previous studies, our results suggest an inverse association between coffee drinking, alcohol consumption and PD. The multiple inverse association observed may indicate a complex interaction between genetic and environmental factors.     

Dose-dependent protective effect of coffee, tea, and smoking in Parkinson's disease: a study in ethnic Chinese

INTRODUCTION: Few studies have examined the relationship of coffee and tea in Parkinson's disease (PD). The potential protective effect of coffee intake and risk of PD has not been studied in a Chinese population. There is a high prevalence of caffeine takers among Chinese in our population. OBJECTIVE: We undertook a case control study to examine the relationship between coffee and tea drinking, cigarette smoking, and other enviromental factors and risk of PD among ethnic Chinese in our population. METHODS AND RESULTS: 300 PD and 500 population controls were initially screened. Two hundred case control pairs matched for age, gender, and race were finally included in the analysis. Univariate analysis revealed significant association of PD with coffee drinking (p<0.0005), tea drinking (p=0.019), alcohol drinking (p=0.001), cigarette smoking (p<0.0005), and exposure to heavy metals (p=0.006). Conditional logistic regression analysis demonstrated that amount of coffee drunk (OR 0.787, 95%CI 0.664-0.932, p=0.006), amount of tea drunk (OR 0.724, 95%CI 0.559-0.937, p=0.014), number of cigarettes smoked (OR 0.384, 95%CI 0.204-0.722, p=0.003), history of heavy metal and toxin exposure (OR 11.837, 95%CI 1.075-130.366, p=0.044), and heart disease (OR 5.518, 95%CI 1.377-22.116, p=0.016) to be significant factors associated with PD. One unit of coffee and tea (3 cups/day for 10 years) would lead to a 22% and 28% risk reduction of PD. One unit of cigarette smoke (3 packs/day for 10 years) reduced the risk of PD by 62%. CONCLUSIONS: We demonstrated a dose-dependent protective effect of PD in coffee and tea drinkers and smokers in an ethnic Chinese population. A history of exposure to heavy metals increased the risk of PD, supporting the multifactorial etiologies of the disease.     

Influence of coffee drinking and cigarette smoking on the risk of primary late onset blepharospasm: evidence from a multicentre case control study

Prior coffee and smoking habits were investigated in a multicentre case control study involving 166 patients presenting with primary late onset blepharospasm (BSP), 228 hospital control patients with primary hemifacial spasm and 187 population control subjects from five Italian centres. Information on age at disease onset, smoking and coffee drinking status at the reference age and average number of cups of coffee drunk/cigarettes smoked per day reached high and similar test-retest reproducibility in case and control patients. Unadjusted logistic regression analysis yielded a significant inverse association of prior coffee drinking and cigarette smoking with case status for the control groups. After adjustment for age, sex, referral centre, disease duration, years of schooling and ever coffee drinking/cigarette smoking, as appropriate, the smoking estimate lacked significance whereas the association of coffee intake and BSP did not (cases vs hospital control patients: OR 0.37 (95% CI 0.20 to 0.67); cases vs population control subjects: OR 0.44 (95% CI 0.23 to 0.85)). The strength of the inverse association between BSP and coffee intake tended to increase with the average number of cups drunk per day. There was a significant correlation between age of BSP onset and number of cups per day (adjusted regression coefficient 1.73; p = 0.001) whereas no correlation was found with number of packs of cigarettes per day. Coffee drinking may be inversely associated with the development of primary BSP and this association may partly depend on the amount consumed.     

Smoking, caffeine, and nonsteroidal anti-inflammatory drugs in families with Parkinson disease

OBJECTIVE: To assess associations between Parkinson disease (PD) and putatively protective factors-smoking, caffeine (coffee, tea, and soft drinks), and nonsteroidal anti-inflammatory drugs (aspirin, ibuprofen, and naproxen). DESIGN: Family-based case-control study. SETTING: Academic medical center clinic. PARTICIPANTS: A total of 356 case subjects and 317 family controls who self-reported environmental exposures. MAIN OUTCOME MEASURES: Associations between PD and environmental measures (history, status, dosage, duration, and intensity) of smoking, coffee, caffeine, nonsteroidal anti-inflammatory drugs, and non-aspirin nonsteroidal anti-inflammatory drugs were examined using generalized estimating equations with an independent correlation matrix while controlling for age and sex. RESULTS: Individuals with PD were significantly less likely to report ever smoking (odds ratio = 0.56; 95% confidence interval, 0.41-0.78). Additional measures of smoking revealed significant inverse associations with PD (P<.05) and trends in odds ratios (P<.005). Increasing intensity of coffee drinking was inversely associated with PD (test for trend P = .05). Increasing dosage (trend P = .009) and intensity (trend P = .01) of total caffeine consumption were also inversely associated, with high dosage presenting a significant inverse association for PD (odds ratio = 0.58; 95% confidence interval, 0.34-0.99). There were no significant associations between nonsteroidal anti-inflammatory drugs and PD. CONCLUSIONS: Inverse associations of smoking and caffeine were corroborated using families with PD, thus emphasizing smoking and caffeine as important covariates to consider in genetic studies of PD.     

Coffee and tea consumption and the risk of Parkinson's disease.

Several prospective studies have assessed the association between coffee consumption and Parkinson's disease (PD) risk, but the results are inconsistent. We examined the association of coffee and tea consumption with the risk of incident PD among 29,335 Finnish subjects aged 25 to 74 years without a history of PD at baseline. During a mean follow-up of 12.9 years, 102 men and 98 women developed an incident PD. The multivariate-adjusted (age, body mass index, systolic blood pressure, total cholesterol, education, leisure-time physical activity, smoking, alcohol and tea consumption, and history of diabetes) hazard ratios (HRs) of PD associated with the amount of coffee consumed daily (0, 1-4, and > or = 5 cups) were 1.00, 0.55, and 0.41 (P for trend = 0.063) in men, 1.00, 0.50, and 0.39 (P for trend = 0.073) in women, and 1.00, 0.53, and 0.40 (P for trend = 0.005) in men and women combined (adjusted also for sex), respectively. In both sexes combined, the multivariate-adjusted HRs of PD for subjects drinking > or = 3 cups of tea daily compared with tea nondrinkers was 0.41 (95% CI 0.20-0.83). These results suggest that coffee drinking is associated with a lower risk of PD. More tea drinking is associated with a lower risk of PD.     

Voluptuary habits and clinical subtypes of Parkinson's disease: The FRAGAMP case–control study

We evaluated the possible association between smoking, coffee drinking, and alcohol consumption and Parkinson's disease (PD). The FRAGAMP study is a large Italian multicenter case–control study carried out to evaluate the possible role of environmental and genetic factors in PD. Adjusted ORs were estimated using unconditional logistic regression. Smoking, coffee, and alcohol consumption were also considered as surrogate markers of lifestyle and analysis was carried out considering the presence of at least one, two, or three factors. This latter analysis was separately performed considering Tremor‐Dominant (TD) and Akinetic‐Rigid (AR) patients. Four hundred ninety‐two PD patients (292 men and 200 women) and 459 controls (160 men and 299 women) were enrolled in the study. Multivariate analysis showed a significant negative association between PD and cigarette smoking (OR 0.51; 95%CI 0.36–0.72), coffee drinking (OR 0.61; 95%CI 0.43–0.87) and wine consumption (OR 0.62; 95%CI 0.44–0.86); a significant trend dose‐effect (P < 0.05) has been found for all the factors studied. We have also found a trend dose‐effect for the presence of at least one, two or three factors with a greater risk reduction (83%) for the presence of three factors. However, a different strength of association between TD and AR was found with a greater risk reduction for the AR patients. We found a significant inverse association between PD smoking, coffee, and alcohol consumption. When analysis was carried out considering the association of these factors as possible surrogate markers of a peculiar lifestyle the association was stronger for the AR phenotype. © 2010 Movement Disorder Society.     

Diabetes preceding Parkinson's disease onset. A case–control study

ObjectiveTo assess the association between diabetes preceding Parkinson's disease (PD) and PD.MethodsPD individuals were matched to PD free individuals randomly selected from people in the same municipality as the cases. Occurrence of diabetes preceding PD onset among cases and controls was assessed through a structured questionnaire. Information regarding current and past medical treatment and other variables was also collected. We used univariate and multivariate logistic models to calculate crude and adjusted odds ratios (OR). Covariates are adjusted for included education, smoking habit, alcohol and coffee consumption.Results318 PD individuals (165 women, 153 men) and 318 matched controls were included in the study. PD patients had a mean age at interview of 66.7 years. Mean age at PD onset was 60.8 years and mean PD duration 5.9 years. We found an inverse association between PD and diabetes preceding PD onset in all groups stratified by gender, age at PD onset, body mass index (BMI), smoking habit, alcohol and coffee consumption. Multivariate analysis yielded the same findings after controlling for the variables (adjusted OR 0.4; 95% CI, 0.2–0.8).ConclusionsOur findings provide additional support for a potential link between diabetes and PD.     

Lifestyle factors and multiple sclerosis: A case-control study in Belgrade

The aim of this case-control study was to assess the risk of developing multiple sclerosis (MS) associated with certain lifestyle factors (cigarette smoking and coffee and alcohol consumption). The study groups consisted of 210 cases with clinically proven and/or laboratory-confirmed MS (Poser's criteria) and an identical number of sex- and age-matched hospital controls. In the MS patients, cigarette smoking was significantly more frequent than in the controls (OR = 1.6, p = 0.021). A dose-response relationship between the risk of MS and both duration (years) of smoking (p = 0.027) and number of cigarettes smoked daily (p = 0.021) was observed. Coffee consumption was significantly more frequent in the MS group (OR = 1.7, p = 0.047), with dose-response relationships. The analysis of alcohol drinking showed a significant association between consumption of hard liquor per day and risk of MS (OR = 6.7, p = 0.026). In multivariate logistic regression analysis, smoking was detected to be a significant independent risk factor for MS (OR = 2.4, p = 0.004).     

Smoking and tea consumption delay onset of Parkinson's disease

Cigarette smoking, coffee and tea drinking may protect against Parkinson's disease (PD). These factors were assessed, retrospectively, to measure their effect on the age of PD onset. The study population consisted of 278 consecutive PD patients. Smoking > or =10 pack-years delayed age of PD onset by 3.2 years (p<0.05). Consumption of tea more than 3 cups per day delayed age of motor symptoms onset by 7.7 years (p<0.01). Coffee consumption exceeding 3 cups per day advanced the age of PD onset by 4.8 years (p=0.03). Thus, tea consumption and smoking can delay the age of PD onset, while coffee drinking may have the opposite effect.     

Premorbid smoking, alcohol consumption, and coffee drinking habits in Parkinson's disease: a case-control study.

A number of studies have reported lower cigarette consumption in patients with Parkinson's disease (PD) previous to onset of the disease. In an attempt to determine whether there existed a "premorbid attitude" by patients against the use of socially accepted "drugs," the premorbid tobacco, alcohol, and coffee consumption habits were compared in 128 PD patients and 256 controls. Patients and controls were selected by case control method and were recruited from the same health area and socioeconomic stratum. In males, the habits of smoking more than 10 cigarettes/day (p < 0.001) and drinking more than 50 g/day of alcohol (p < 0.001) were significantly less frequent in the PD patients than in the controls, but the differences in coffee consumption were nonsignificant. In females behavior did not differ significantly between the PD group and the controls for any of the three habits. There was no correlation between the amount of smoking and alcohol drinking and age at onset of PD or current Hoehn and Yahr's staging. Our results suggest the existence of a premorbid personality in males with PD, possibly conditioning a restrictive attitude toward the consumption of such toxic substances as tobacco and alcohol, yet a more tolerant attitude toward habits more widely accepted socially, like coffee consumption.     

Combined effects of smoking,coffee, and NSAIDs on Parkinson's disease risk

Inverse associations of Parkinson's disease (PD) with cigarette smoking, coffee drinking, and nonsteroidal anti‐inflammatory drug (NSAID) use have been reported individually, but their joint effects have not been examined. To quantify associations with PD for the individual, two‐way and three‐way combinations of these factors, a case–control association study with 1,186 PD patients and 928 controls was conducted. The study setting was the NeuroGenetics Research Consortium. Subjects completed a structured questionnaire regarding smoking, coffee, and NSAID consumption. Odds ratios were calculated using unconditional logistic regression. Smoking, coffee, and over the counter NSAID use as individual factors exhibited significantly reduced risks of 20% to 30%. The two‐way and three‐way combinations were associated with risk reduction of 37% to 49%, and 62%, respectively. Smoking and coffee exhibited significant inverse risk trends with increasing cumulative exposures, suggesting dose–response relations. With respect to the combination of all three exposures, persons who were at the highest exposure strata for smoking and coffee and used NSAIDs had an estimated 87% reduction in risk (OR = 0.13, 95% CI = 0.06–0.29). Whether this finding reflects true biologic protection needs to be investigated. © 2007 Movement Disorder Society     

Alcohol and risk of Parkinson's disease in a large, prospective cohort of men and women

Addictive behaviors, such as cigarette smoking and coffee drinking, have been associated with a reduced risk of Parkinson's disease (PD). Whether alcohol consumption is also associated with PD risk is less certain. We prospectively followed 132,403 participants in the Cancer Prevention Study II Nutrition Cohort from 1992 to 2005. Alcohol intake was assessed at baseline. Incident cases of PD (n = 605; 389 male and 216 female) were confirmed by treating physicians and medical record review. Relative risks (RRs) were estimated using proportional hazards models, adjusting for age, smoking, and other risk factors. Alcohol consumption was not significantly associated with PD risk. After adjustment for age, smoking, and other risk factors, the RR comparing men consuming 30 or more grams of alcohol per day (highest category) to nondrinker men was 1.29 (95% confidence interval [CI]: 0.90, 1.86; P trend: 0.40), and the RR comparing women consuming 15 or more grams of alcohol (highest category) per day to nondrinker women was 0.77 (95% CI: 0.41, 1.45; P trend: 0.87). Consumption of beer, wine, or liquor was also not associated with PD risk. The results of this large, prospective study do not support an association between alcohol intake and risk of PD.     

Differential effect of environmental risk factors on postural instability gait difficulties and tremor dominant Parkinson's disease

Both environmental and genetic factors contribute to the development of Parkinson's disease (PD). We have examined environmental risk factors in a Norwegian population of incident PD patients and controls, the Norwegian ParkWest study. All five neurological wards in the study area of Western Norway participated in the study. A 4‐step diagnostic procedure was used to establish a representative cohort of patients with incident PD at a high level of diagnostic accuracy. 212 incident PD patients and 175 age‐ and gender‐matched controls were included. PD patients and controls were asked for information on occupation, education, exposure to pesticides, tobacco, alcohol, and caffeine. Agricultural work was associated with a higher risk of PD (OR 1.75 (1.03–3.0) P = 0.009). There were no differences as to other occupations. Smoking (OR 0.63 (0.42–0.95) P = 0.016) and alcohol use (OR 0.55 P = 0.008) were associated with a lower risk for PD. Interestingly, this inverse association was only seen in postural instability gait difficulties (PIGD) PD (P = 0.046 for smoking, P = 0.07 for alcohol consumption), and not in tremor dominant (TD) PD which was similar to controls. Consumption of coffee was lower in PD patients (3.3 ± 1.8 cups per day vs. 3.8 ± 2.0 in controls P = 0.02). In the regression model including intake of alcohol, coffee, and smoke, only coffee (P = 0.007) and alcohol intake (P = 0.021) remained significant whereas smoking was no longer significant. Thus, it seems as though only coffee intake reduces the risk of PD in general while associations to alcohol and smoking differ between PIGD and TD‐PD patients. © 2010 Movement Disorder Society     

Number of children and risk of Parkinson's disease.

We investigated the association between number of children and Parkinson's disease (PD) in two independent studies. In a case-control study, we identified all subjects who developed PD in Olmsted County, MN, from 1976 through 1995, and matched them individually by age (+/-1 year) and sex to population controls (193 cases and 193 controls). The replication study was a population-based cohort study of 6,341 subjects from Rotterdam, the Netherlands (2,610 men). In the Olmsted County study, men who fathered at least one child had an increased risk of PD (unadjusted OR, 2.7; 95% CI, 1.2-6.1; P = 0.02), and the risk increased with increasing number of children. The findings in women were not significant. In the Rotterdam Study, the risk of PD increased significantly with increasing number of children in men (test for linear trend, unadjusted; P = 0.04), but not in women. The findings from both studies remained consistent in direction but reduced in magnitude of the association, and lost significance after simultaneous adjustment for education, cigarette smoking, alcohol consumption, and coffee consumption. The independent replication in two distinct populations and using different epidemiologic study designs may suggest a link between the number of children and PD restricted to men.     

Relationship between impulsive sensation seeking traits, smoking, alcohol and caffeine intake, and Parkinson's disease

BACKGROUND: An inverse relation exists between smoking and coffee intake and Parkinson's disease (PD). The present study explored whether this is explained by low sensation seeking, a personality trait believed to characterise PD. METHODS: A total of 106 non-demented patients with PD and 106 age and sex matched healthy controls completed a short version of Zuckerman's Sensation Seeking Scale (SSS), the Geriatric Depression Scale, and the Trait Anxiety Inventory. Data were collected on past and current cigarette smoking, and participants also completed food frequency questionnaires to estimate current caffeine and alcohol intake. RESULTS: Patients with PD had lower sensation seeking and higher depression and anxiety scores. They were also less likely to have ever smoked, and had lower caffeine and alcohol intakes. Analysis of the data using conditional logistic regression suggested that the inverse association of PD risk with sensation seeking was independent of smoking, and caffeine and alcohol intake. Moreover, low sensation seeking explained some of the apparent effect of caffeine and alcohol intake on PD. However, the effect of smoking was weakened only slightly when SSS was included in the regression model. CONCLUSION: This study raises the possibility that there is a neurobiological link between low sensation seeking traits--which might underlie the parkinsonian personality--and the hypothetical protective effect of cigarette smoking and caffeine consumption on PD.     

The effect of cigarette smoking, tea, and coffee consumption on the progression of Parkinson's disease

Previous epidemiological studies found a negative association between cigarette smoking, tea or coffee drinking with the occurrence of Parkinson's disease (PD). However, it is unknown how these factors affect the rate of progression of the disease. A retrospective study was conducted among 278 consecutive PD patients. Data on smoking and coffee or tea consumption were obtained through direct or proxy interviews, and the time from onset of motor symptoms until reaching Hoehn & Yahr (H&Y) stage 3 was retrieved from the case records. Cox proportional hazards model and Kaplan-Meyer model were used to estimate whether the dependent variables (smoking, drinking coffee or tea) affect the rate of progression of the disease, which was measured by the time it took patients to reach H&Y stage 3. We found that disease progression was not affected by cigarette smoking, tea or coffee consumption. The present study suggests that these variables do not have a disease modifying effect in already diagnosed PD patients.     

Risk factors for aneurysmal subarachnoid haemorrhage: the Tromsø study

Methods: The Tromsø health study is a population based survey of risk factors for cardiovascular disease in 27 161 subjects. 26 cases of aneurysmal SAH were identified in which risk factors were registered before the bleeding. Four age and sex matched controls were selected for each case. A backward logistic regression analysis was conducted and odds ratios (ORs) for significant risk factors were calculated. Systolic and diastolic blood pressure, cigarette smoking habits, serum concentrations of lipoproteins, body mass index, and coffee consumption were analysed. Results: The crude annual incidence rate of aneurysmal SAH was 8.84/100 000 population. The proportion of current smokers was significantly (p = 0.003) higher in patients with SAH (73.1%) than in controls (41.3%). Drinking more than five cups of coffee per day was more common among patients (85%) than controls (59%) (p = 0.004). Mean (SD) systolic blood pressure was higher (p = 0.017) in patients (154.0 (32.5)) than in controls (136.3 (23.3)). Regression analysis showed that cigarette smoking (p = 0.04), systolic blood pressure (p < 0.0001), and coffee consumption (p = 0.004) were independent risk factors for SAH. The OR of current smokers versus never smokers was 4.55 (95% confidence interval (CI) 1.08 to 19.30) and the OR of drinking more than five cups of coffee a day was 3.86 (95% CI 1.01 to 14.73). The OR of an increase in systolic blood pressure of 20 mm Hg was 2.46 (95% CI 1.52 to 3.97). Conclusions: Cigarette smoking and hypertension are significant independent risk factors for aneurysmal SAH. A high coffee consumption may also predispose patients to aneurysmal SAH.     

帕金森病与饮茶的病例对照研究

目的探讨饮茶同原发性帕金森病(PD)的关系。方法采用以人群为基础的病例对照研究,调查在北京地区55岁以上PD患病率调查中确诊及2002年8月至2003年1月在北京协和医院帕金森研究中心诊治的病人共114例;以及性别、民族及居住地与其匹配的对照205例。采用统一的危险因素结构式问卷和诊断标准对所有对象的社会人口学资料和个人的生活习惯:饮茶、吸烟、饮酒及一级亲属的家族史因素与PD发病情况进行调查,应用单因素和多因素分析方法对有关因素进行分析。结果在饮茶与PD关系的单因素分析中,以非饮茶人群为对照,饮茶者患PD的比值比(OR)为0.23(95%CI:0.14,0.62;P<0.01)。经多因素的非条件Logistic回归分析后,饮茶者的OR值为0.199(95%CI:0.114,0.345;P<0.001)。结论北京地区居民中饮茶与帕金森病呈显著负相关联,为PD的保护性因素。     

生活习性与帕金森病关系的研究

目的 探讨生活习性与帕金森病(PD)的关系。方法 选取在北京地区55岁以上PD患病率调查中确诊及在北京协和医院帕金森病研究中心诊治的患者共114例；以及性别、民族及居住地与其匹配的对照者205名的一般资料及吸烟、饮茶、饮酒等生活习性进行调查，并加以相关分析。结果 吸烟者和饮茶者患PD的危险性低于对照组，OR值分别为0．538(95％CI：0．290，0．998)和0．199(95％CI：0.114，0．346)。饮酒者与PD关联无统计学意义。结论 生活习性中吸烟和饮茶同PD存在负相关，即有保护作用，而饮酒与PD的发病无关。     

Cigarette smoking and Parkinson's disease: a case-control study in a population characterized by a high prevalence of pesticide exposure.

Epidemiological studies have been consistent in showing that cigarette smoking is inversely associated with Parkinson's disease (PD), whereas pesticide use is positively associated with PD. However, the relationship between PD and cigarette smoking remains poorly understood. Our objective was to study the relationship between cigarette smoking and PD in a population characterized by a high prevalence of pesticide exposure. This case-control study was carried out among subjects enrolled in the Mutualite Sociale Agricole, the French health insurance organization for workers connected to the agricultural world. We included 247 cases and 676 controls matched on age, sex, and region of residency. Information on smoking was obtained through in-person interviews. Pesticide exposure was assessed using a case-by-case expert evaluation procedure. We found an inverse relationship between ever cigarette smoking and PD (odds ratio [OR] = 0.6; 95% confidence interval [CI] = 0.4-0.9). The strength of this association increased with the number of pack-years. This relationship was present even when smoking was considered as long as 40 years before PD onset. An inverse association was also present among subjects professionally exposed to pesticides (OR = 0.5; 95% CI = 0.3-0.8) and was independent of the duration of exposure among men. We confirm the inverse association between cigarette smoking and PD in a population characterized by a high prevalence of professional pesticide exposure. The relationship between PD and cigarette smoking was not significantly modified or confounded by exposure to pesticides.