Environmental determinants of Parkinson's disease

Well-Water Consumption and Risk of Parkinson's Disease: A Meta-Analysis of 15 Observational Studies

INTRODUCTION

The relationship between the risk of Parkinson disease and well-water consumption has been extensively studied, but the results have been contradictory. Therefore, we conducted a meta-analysis of observational studies to systematically assess the relationship between well-water consumption and Parkinson disease risk.

METHODS

We followed the PRISMA checklist in completing the meta-analysis. We searched two electronic databases (PubMed, EBSCO, EMBASE and Cochrane) from establishment to October, 2021, to identify relevant studies linking well-water drinking to Parkinson risk. We used a random-effects model to calculate the overall odds ratio (OR) with 95% confidence interval (CI). To reduce intragroup heterogeneity, we conducted subgroup analyses according to the research design and geographic area.

RESULTS

After careful review, a total of 15 case-control-designed studies included data suitable for our meta-analysis. The total number of cases and total controls that contribute to the combined OR were 2182 and 2456. The combined OR for ever well-water drinkers versus non-drinkers was 1.16 (95% CI: 0.97-1.39, I² = 44.52%). In subgroup analysis by geographic area, a significant association was observed in studies conducted in Asia (OR 1.29, 95% CI: 1.05-1.58, I² = 0.0%, p for heterogeneity = 0.460) but not in studies conducted in America (OR 0.97, 95% CI: 0.76-1.24, I² = 41.2%, p for heterogeneity = 0.164). In subgroup analysis by study design, a borderline significant association emerged in hospital-based case-control studies (OR 1.31, 95% CI: 1.04-1.65, I² = 40.9%, p for heterogeneity = 0.118) but not in population-based case-control studies (OR 0.96, 95% CI: 0.73-1.26, I² = 41.1%, p for heterogeneity = 0.165).

DISCUSSION

Our results indicate that there is no significant correlation between well-water consumption and PD risk.

Clinical Features and Risk Factors of Parkinson's Disease in a Population of Khyber Pakhtunkhwa, Pakistan: A Case-Control Study

BACKGROUND

Parkinson's disease (PD) is one of the most common neurological disorders that mostly affect aged individuals. The common symptoms of PD are rest tremor, bradykinesia, and rigidity.

OBJECTIVES

The present study was devised to find out the clinical features and risk factors associated with PD in a population of Khyber Pakhtunkhwa.

METHODS

A total of 600 PD patients and 1,200 control individuals took part in this study. The participants filled out a standard questionnaire.

RESULTS

This study found a significant association between PD and exposure to pesticides (p < 0.0001) and doing work on farms (p < 0.0001). The use of aldrin was significantly associated with PD (p < 0.0001). Furthermore, we also found that PD status was associated with individuals who have a history of depression, hypertension, head injury, and Alzheimer's disease. This study also showed that the PD rate was lower in those who were using tobacco products.

CONCLUSION

In this case-control study, we revealed some environmental and medical conditions that are linked with PD. To control the disease, we must minimize exposure to pesticides, and the government and scientific community should play their role.

Well Water and Parkinson's Disease in Medicare Beneficiaries: A Nationwide Case-Control Study

BACKGROUND

Well water frequently is considered a risk factor for Parkinson's disease (PD), but few studies were designed appropriately to test whether geographic factors affect PD risk.

OBJECTIVE

To determine the risk of PD in relation to residential use of private well water.

METHODS

In a nationwide, population-based case-control study, we identified all incident PD cases (N = 89,790) and all comparable controls (N = 21,549,400) age 66-90 who solely relied on Medicare coverage in the U.S. in 2009. We estimated the probability of use of private well water using zip code of residence at diagnosis/reference and U.S. Census data on household water source. We modeled this exposure linearly in logistic regression to calculate the odds ratio (OR) and 95% confidence interval (CI) of PD risk in relation to well water use. We adjusted for age, sex and race/ethnicity, and verified that smoking and use of medical care did not confound results. We repeated analyses with a 2-year exposure lag and separately within each U.S. state.

RESULTS

Use of well water was inversely associated with PD risk (OR = 0.87, 95% CI 0.85-0.89). We confirmed this association in a Cox survival analysis in which we followed controls for 5 years, death or PD diagnosis. There was little evidence that well water use increased risk of PD in any individual state.

CONCLUSIONS

Although it remains possible that exposures in well water in more narrow geographic regions increase PD risk, in general these results suggest that exposures more common in urban/suburban areas might also be relevant.

Association between Parkinson's Disease and Cigarette Smoking, Rural Living, Well-Water Consumption, Farming and Pesticide Use: Systematic Review and Meta-Analysis

Objective

Bradford Hill’s viewpoints were used to conduct a weight-of-the-evidence assessment of the association between Parkinson’s disease (PD) and rural living, farming and pesticide use. The results were compared with an assessment based upon meta-analysis. For comparison, we also evaluated the association between PD and cigarette smoking as a “positive control” because a strong inverse association has been described consistently in the literature.

Methods

PubMed was searched systematically to identify all published epidemiological studies that evaluated associations between Parkinson’s disease (PD) and cigarette smoking, rural living, well-water consumption, farming and the use of pesticides, herbicides, insecticides, fungicides or paraquat. Studies were categorized into two study quality groups (Tier 1 or Tier 2); data were abstracted and a forest plot of relative risks (RRs) was developed for each risk factor. In addition, when available, RRs were tabulated for more highly exposed individuals compared with the unexposed. Summary RRs for each risk factor were calculated by meta-analysis of Tier 1, Tier 2 and all studies combined, with sensitivity analyses stratified by other study characteristics. Indices of between-study heterogeneity and evidence of reporting bias were assessed. Bradford Hill’s viewpoints were used to determine if a causal relationship between PD and each risk factor was supported by the weight of the evidence.

Findings

There was a consistent inverse (negative) association between current cigarette smoking and PD risk. In contrast, associations between PD and rural living, well-water consumption, farming and the use of pesticides, herbicides, insecticides, fungicides or paraquat were less consistent when assessed quantitatively or qualitatively.

Conclusion

The weight of the evidence and meta-analysis support the conclusion that there is a causal relationship between PD risk and cigarette smoking, or some unknown factor correlated with cigarette smoking. There may be risk factors associated with rural living, farming, pesticide use or well-water consumption that are causally related to PD, but the studies to date have not identified such factors. To overcome the limitations of research in this area, future studies will have to better characterize the onset of PD and its relationship to rural living, farming and exposure to pesticides.

Onset and progression factors in Parkinson's disease: A systematic review

Current research has identified several factors thought to be associated with the onset and progression of Parkinson's Disease (PD); however, whether certain factors contribute to or are protective against PD remains unclear. As such, a systematic search of the literature was performed using variations of MeSH and keyword search terms to identify and summarize systematic reviews and primary studies pertaining to factors associated with the onset and progression of PD. Factors referred to both traditional risk factors and prodromal markers. The following databases were searched: MEDLINE, MEDLINE In-Process, EMBASE, PsycINFO, Scopus, Web of Science, Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature (CINAHL), ProQuest Dissertations & Theses, AARP AgeLine, and PDGene. A quality assessment of included systematic reviews was completed using the validated Assessment of the Methodological Quality of Systematic Reviews (AMSTAR) tool. Data extraction targeted reported factors, risk estimates, and 95% confidence intervals (CI). Findings identified 11 systematic reviews of sufficient quality reporting factors for PD onset, and no systematic reviews reporting factors for PD progression. In addition, 93 primary articles were identified, of which, 89 articles addressed factors related to PD onset and 4 articles addressed factors related to the PD progression. Pesticide exposure, rural living, well-water drinking, and farming occupation were consistently found to be positively associated with the onset of PD. Moreover, family history and polymorphisms to key genes were also found to be positively associated with the onset of PD. Conversely, coffee consumption, cigarette smoking, and some polymorphisms were consistently found to be negatively associated with the onset of PD. Urate was the only identified factor linked to the progression of PD; it was mostly found to be negatively associated with PD. In sum, the evidence was systematically found and summarized in the literature pertaining to factors related to the onset and progression of PD.

Head injury and risk for Parkinson disease: results from a Danish case-control study

OBJECTIVE

To examine the association between head injuries throughout life and the risk for Parkinson disease (PD) in an interview-based case-control study.

METHODS

We identified 1,705 patients diagnosed with PD at 10 neurologic centers in Denmark in 1996-2009 and verified their diagnoses in medical records. Patients were matched to 1,785 controls randomly selected from the Danish Central Population Register on sex and year of birth. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression.

RESULTS

We observed no association between any head injury before first cardinal symptom and PD (OR 1.02; 95% CI 0.88, 1.19). Examination of number of head injuries (1: OR 1.02; 95% CI 0.87, 1.20; ≥2: OR 1.03; 95% CI 0.72, 1.47) or hospitalization for a head injury (OR 0.89; 95% CI 0.70, 1.12) did not show an association with PD. For 954 study subjects with at least one head injury, there was no evidence of an association between loss of consciousness (OR 0.89; 95% CI 0.67, 1.17), duration of loss of consciousness (≤1 minute: OR 0.93; 95% CI 0.58, 1.49; 1-5 minutes: OR 0.74; 95% CI 0.51, 1.08; ≥5 minutes: OR 0.81; 95% CI 0.53, 1.24), or amnesia (OR 1.31; 95% CI 0.88, 1.95) and risk for PD. Application of a lag time of 10 years between head injury and first cardinal symptom resulted in similar risk estimates.

CONCLUSIONS

The results do not support the hypothesis that head injury increases the risk for PD.

A study on risk factors for Parkinson׳s disease in Indian population

Parkinson׳s disease is the second most common neurodegenerative disorder. The exact cause of selective dopaminergic neurodegeneration is unknown, but it is supposed that etiology of Parkinson׳s disease is multifactorial and consists of an interaction between environmental factors and genetic predisposition. To find out the association between environmental factors and risk of Parkinson׳s disease, a case control study was designed including 97 Parkinson׳s disease patients and 97 controls. Logistic regression analysis was used to determine the risk factors for Parkinson׳s disease. Results from the present study showed that gender, religion, education, place of living, occupation, dietary habits, tobacco chewing, smoking, alcohol intake, and head injury had no association with PD. However, chemical exposure and well water drinking were significantly associated with PD, which concluded that environmental factors could act as a risk factor for PD in some way.

Parkinson's disease and pesticide exposure--a new assessment

Parkinson's disease (PD) is an idiopathic disease and its pathological feature is a loss of pigmented neurons in the substantia nigra. Some commonly used pesticides possess neurotoxicity, and exposure to such compounds may trigger mechanisms similar to those in the development of idiopathic PD. We conducted a systematic review of epidemiological studies, aiming at a critical evaluation of the association between the development of PD and pesticide exposure. Reported effect sizes (ES) in the relevant studies were pooled into the meta-analysis to derive summary ES. The summary ES suggested a significantly positive association between PD and overall pesticide use (non-occupational and/or occupational pesticide use) [1.42; 95% confidence interval (CI) 1.32 to 1.52, the fixed-effects model], as well as between PD and occupational pesticide exposure (1.49 with a 95% CI of 1.34-1.66). Both occupational herbicide and occupational insecticide exposure showed a significant association with PD. The results of the meta-analysis reported in this study suggest the existence of a statistically positive association between PD and pesticide exposure. The majority of the studies that were pooled in the meta-analysis were case-control design with very few cohort studies and most with poor exposure characterization thus, any further case-control studies using similar methodologies are unlikely to have a significant impact or understanding on the currently-reported association between pesticide exposure and the development of idiopathic PD. Therefore, we believe that if further epidemiological studies are going to be conducted in the area, they should be prospective cohort studies that will include accurate exposure assessment.

Examining the relationship between head trauma and neurodegenerative disease: A review of epidemiology, pathology and neuroimaging techniques

Traumatic brain injuries (TBI) are induced by sudden acceleration-deceleration and/or rotational forces acting on the brain. Diffuse axonal injury (DAI) has been identified as one of the chief underlying causes of morbidity and mortality in head trauma incidents. DAIs refer to microscopic white matter (WM) injuries as a result of shearing forces that induce pathological and anatomical changes within the brain, which potentially contribute to significant impairments later in life. These microscopic injuries are often unidentifiable by the conventional computed tomography (CT) and magnetic resonance (MR) scans employed by emergency departments to initially assess head trauma patients and, as a result, TBIs are incredibly difficult to diagnose. The impairments associated with TBI may be caused by secondary mechanisms that are initiated at the moment of injury, but often have delayed clinical presentations that are difficult to assess due to the initial misdiagnosis. As a result, the true consequences of these head injuries may go unnoticed at the time of injury and for many years thereafter. The purpose of this review is to investigate these consequences of TBI and their potential link to neurodegenerative disease (ND). This review will summarize the current epidemiological findings, the pathological similarities, and new neuroimaging techniques that may help delineate the relationship between TBI and ND. Lastly, this review will discuss future directions and propose new methods to overcome the limitations that are currently impeding research progress. It is imperative that improved techniques are developed to adequately and retrospectively assess TBI history in patients that may have been previously undiagnosed in order to increase the validity and reliability across future epidemiological studies. The authors introduce a new surveillance tool (Retrospective Screening of Traumatic Brain Injury Questionnaire, RESTBI) to address this concern.

BST1 rs11724635 interacts with environmental factors to increase the risk of Parkinson's disease in a Taiwanese population

A recently published genome-wide association study in Caucasian and Asian populations showed a significant association between the bone marrow stromal cell antigen 1 (BST1) SNP rs11724635 and increased risk for Parkinson's disease (PD). To investigate whether BST1 rs11724635 increases the risk of PD, either by itself or in combination with environmental factors, we performed an association analysis of BST1 rs11724635 in a large cohort of Taiwanese patients with PD and age matched controls. The study used TaqMan genotyping, logistic regression, and haplotype methods. The genotype distribution of rs11724635 in PD patients (N = 468; p = 0.50) and control subjects (N = 487; p = 0.44) was consistent with Hardy-Weinberg equilibrium. Compared with the AA genotype, the frequency of both CA and CC genotypes was not significantly different between the patient and control groups. The adjusted odd ratios (ORs) for CA and CC were not statistically significant (CA: OR = 0.962, 95% CI = 0.643-1.439, p = 0.850; CC: OR = 0.992, 95% CI = 0.654-1.503, p = 0.969). Of note, ever use of well water before the onset of PD symptoms had an impact on the occurrence of PD through interactions with BST1 rs11724635 AC (OR = 1.453, p = 0.024) and CC (OR = 1.623, p = 0.008). Our results show that the BST1 rs11724635 polymorphism alone is not associated with the development of PD, but it can interact with well water drinking to increase the risk of PD in this Taiwanese population.

Head injury and risk of Parkinson disease: a systematic review and meta-analysis

Head trauma has been implicated in the etiopathogenesis of Parkinson's disease (PD). We performed a meta-analysis to investigate the association between head trauma and the risk of developing PD. We included observational studies if they (1) clearly defined PD, (2) defined head trauma leading to concussion, and (3) presented odds ratios (ORs) and 95% confidence intervals (CIs) or provided data to compute these statistics. Random effect model was used to estimate the pooled, adjusted OR. Heterogeneity between studies was evaluated with the Q test and the I(2) statistic. We conducted a sensitivity analysis to assess the influence of each study and repeated the analysis by excluding the studies with the largest weights. We used funnel plot to assess the presence of publication bias. After reviewing more than 636 article titles, 34 articles were selected for full review. In total, 22 studies (19 case-control studies, 2 nested case-control studies, and 1 cohort study) were included in the meta-analysis. The pooled OR for the association of PD and head trauma was 1.57 (95% CI, 1.35-1.83). The results of our meta-analysis indicate that a history of head trauma that results in concussion is associated with a higher risk of developing PD. © 2013 Movement Disorder Society.

Head injury and Parkinson's disease: a population-based study

BACKGROUND

The epidemiological evidence on head injury and the risk of Parkinson's disease (PD) has been inconsistent.

METHODS

We examined the relation between previous hospitalization for head injury and PD using a population-based nested case-control design based on the Swedish National Patient Register from 2001 until 2007, including 18,648 PD cases and 93,240 controls, randomly selected from the general population. Exposure was defined as hospitalization for head injury between 1987 and index date.

RESULTS

Overall, previous hospitalization resulting from head injury was associated with an increased risk of PD; this association appeared to be largely explained by head injuries experienced recently, especially within 1 year before PD ascertainment.

CONCLUSIONS

Our results do not provide convincing evidence for a causal relationship between head injury later in life and PD.

Pesticide exposure and Parkinson's disease: epidemiological evidence of association

It has been suggested that exposure to pesticides might be involved in the etiology of Parkinson's disease (PD). We conducted an updated systematic review of the epidemiologic literature over the past decade on the relationship between pesticide exposure and PD, using the MEDLINE database. Despite methodological differences, a significantly increased PD risk was observed in 13 out of 23 case-control studies that considered overall exposure to pesticides (risk estimates of 1.1-2.4) and in 10 out of 12 studies using other research designs (risk estimates of 2 or higher). Various studies found stronger associations in genetically susceptible individuals. Among a growing number of studies on the effects of exposure to specific pesticides (n=20), an increased PD risk has been associated with insecticides, especially chlorpyrifos and organochlorines, in six studies (odds ratios of 1.8-4.4), and with the herbicide paraquat, the fungicide maneb or the combination of both. Findings considerably strengthen the evidence that exposure to pesticides in well water may contribute to PD, whereas studies of farming and rural residence found inconsistent or little association with the disease. Taken together, this comprehensive set of results suggests that the hypothesis of an association between pesticide exposure and PD cannot be ruled out. However, inadequate data on consistent responses to exposure hinder the establishment of a causal relationship with PD. Given the extensive worldwide use of many pesticides, further studies are warranted in larger populations that include detailed quantitative data on exposure and determination of genetic polymorphisms.

Epidemiology and etiology of Parkinson's disease: a review of the evidence

The etiology of Parkinson's disease (PD) is not well understood but likely to involve both genetic and environmental factors. Incidence and prevalence estimates vary to a large extent-at least partly due to methodological differences between studies-but are consistently higher in men than in women. Several genes that cause familial as well as sporadic PD have been identified and familial aggregation studies support a genetic component. Despite a vast literature on lifestyle and environmental possible risk or protection factors, consistent findings are few. There is compelling evidence for protective effects of smoking and coffee, but the biologic mechanisms for these possibly causal relations are poorly understood. Uric acid also seems to be associated with lower PD risk. Evidence that one or several pesticides increase PD risk is suggestive but further research is needed to identify specific compounds that may play a causal role. Evidence is limited on the role of metals, other chemicals and magnetic fields. Important methodological limitations include crude classification of exposure, low frequency and intensity of exposure, inadequate sample size, potential for confounding, retrospective study designs and lack of consistent diagnostic criteria for PD. Studies that assessed possible shared etiological components between PD and other diseases show that REM sleep behavior disorder and mental illness increase PD risk and that PD patients have lower cancer risk, but methodological concerns exist. Future epidemiologic studies of PD should be large, include detailed quantifications of exposure, and collect information on environmental exposures as well as genetic polymorphisms.

Environmental factors and Parkinson's disease: a case-control study in Belgrade, Serbia

A case-control study was performed in Belgrade in order to investigate the association between Parkinson's disease (PD) and some environmental factors. During the period 2001-2005, 110 new PD cases and 220 hospital controls were interviewed. Cases and controls were matched by sex, age (+/-2 years), and place of residence (urban/rural). According to multivariate conditional logistic regression analysis, PD was positively asssociated with exposure to insecticides (odds ratio (OR) 3.22, 95% confidence interval (95% CI) 1.32-7.87), dyes (OR 25.33; 95% CI, 2.89-222.0), and naphtha and its derivates (OR 9.53; 95% CI, 1.04-86.96), and with gardening (OR 5.51; 95% CI, 3.04-10.01), well water drinking (OR 2.62; 95% CI, 1.40-4.90), and spring water drinking (OR 2.19; 95% CI, 1.15-4.16). Negative association was found for service-sector working (OR 0.15; 95% CI, 0.04-0.59). The results obtained did not changed after adjustment for smoking. The findings of the present study support the role of environmental factors in the occurence of PD.

Well-water consumption and Parkinson's disease in rural California

INTRODUCTION

Investigators have hypothesized that consuming pesticide-contaminated well water plays a role in Parkinson's disease (PD), and several previous epidemiologic studies support this hypothesis.

OBJECTIVES

We investigated whether consuming water from private wells located in areas with documented historical pesticide use was associated with an increased risk of PD.

METHODS

We employed a geographic information system (GIS)-based model to estimate potential well-water contamination from agricultural pesticides among 368 cases and 341 population controls enrolled in the Parkinson's Environment and Genes Study (PEG). We separately examined 6 pesticides (diazinon, chlorpyrifos, propargite, paraquat, dimethoate, and methomyl) from among 26 chemicals selected for their potential to pollute groundwater or for their interest in PD, and because at least 10% of our population was exposed to them.

RESULTS

Cases were more likely to have consumed private well water and to have consumed it on average 4.3 years longer than controls (p = 0.02). High levels of possible well-water contamination with methomyl [odds ratio (OR) = 1.67; 95% confidence interval (CI), 1.00-2.78]), chlorpyrifos (OR = 1.87; 95% CI, 1.05-3.31), and propargite (OR = 1.92; 95% CI, 1.15-3.20) resulted in approximately 70-90% increases in relative risk of PD. Adjusting for ambient pesticide exposures only slightly attenuated these increases. Exposure to a higher number of water-soluble pesticides and organophosphate pesticides also increased the relative risk of PD.

CONCLUSION

Our study, the first to use agricultural pesticide application records, adds evidence that consuming well water presumably contaminated with pesticides may play a role in the etiology of PD.

Alterações do olfato na doença de Parkinson

OBJETIVO: Caracterizar o comprometimento olfatório em 50 pacientes com doença de Parkinson (DP) utilizando o teste de identificação de 12 cheiros da Universidade de Pensilvânia (TICUP), comparando-os com 76 indivíduos normais e associá-lo ao quadro clínico e epidemiológico. MÉTODO: Os pacientes foram avaliados na fase "on" com as escalas unificada da doença de Parkinson (UPDRS), Hoehn e Yahr e TICUP e o grupo controle com o TICUP. RESULTADOS: A média geral do número de acertos foi 5,7 nos parkinsonianos e 9 nos controles, com pontuação menor nos que apresentaram como sintoma inicial tremor e naqueles que atualmente apresentavam tremor, rigidez e bradicinesia. A idade e o estágio da DP correlacionaram-se negativamente com o número de acertos, não havendo correlação da perda olfatória com idade de início do quadro e pontuação da UPDRS. CONCLUSÃO: Apresentaram comprometimento olfatório 80% dos pacientes com DP, sendo essa avaliação ferramenta importante no diagnóstico diferencial.

An in vitro approach to assess the toxicity of certain food contaminants: Methylmercury and polychlorinated biphenyls

Methylmercury (MeHg) and polychlorinated biphenyls (PCBs) are widespread environmental pollutants and food contaminants, and known developmental neurotoxicants. Aim of this study was to evaluate the effects of MeHg, PCB 126 and PCB 153 in a battery of in vitro cell systems. A total of 17 cell types were utilized, including nervous system (neuronal and astroglial) and non-nervous system cells. End-points measured included MTT reduction, Trypan blue exclusion and (3)H-thymidine incorporation into DNA. Results indicate that this approach would identify these three compounds as neurotoxicants, and would also point out to the thyroid (for PCB 126 and MeHg) and the prostate (for both PCBs) as important additional targets. Tests of binary combinations of MeHg and PCBs indicated no interaction and an additive response, in agreement with other recent reports. Cerebellar granule neurons from mice with genetically determined low glutathione levels were more sensitive than wild-type neurons to the toxicity of all three compounds, supporting a role for oxidative stress in their neurotoxicity. These findings provide initial evidence that a relatively rapid in vitro screening approach can be developed, that would provide initial information useful for assessing neurotoxicity, as well as indication on potential other targets of biological action or toxicity.