Lifestyle, family history, and risk of idiopathic Parkinson disease: a large Danish case-control study

Lifestyle Modulators of Neuroplasticity in Parkinson's Disease: Evidence in Human Neuroimaging Studies

Parkinson's disease (PD) is a neurodegenerative disease characterized by both motor and non-motor symptoms. A progressive neuronal loss and the consequent clinical impairment lead to deleterious effects on daily living and quality of life. Despite effective symptomatic therapeutic approaches, no disease-modifying therapies are currently available. Emerging evidence suggests that adopting a healthy lifestyle can improve the quality of life of PD patients. In addition, modulating lifestyle factors can positively affect the microstructural and macrostructural brain levels, corresponding to clinical improvement. Neuroimaging studies may help to identify the mechanisms through which physical exercise, dietary changes, cognitive enrichment, and exposure to substances modulate neuroprotection. All these factors have been associated with a modified risk of developing PD, with attenuation or exacerbation of motor and non-motor symptomatology, and possibly with structural and molecular changes. In the present work, we review the current knowledge on how lifestyle factors influence PD development and progression and the neuroimaging evidence for the brain structural, functional, and molecular changes induced by the adoption of positive or negative lifestyle behaviours.

Alcohol and Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

A substantial body of research has examined the relationship between alcohol consumption and risk of Parkinson's disease (PD).

OBJECTIVE

To provide an updated systematic review and meta-analysis of observational studies examining the relationship between alcohol consumption and risk of PD.

METHODS

Eligible studies comparing PD risk in ever vs. never alcohol drinkers were sourced from six databases. Outcomes were pooled using standard meta-analysis techniques. Separate female and male estimates were generated from studies reporting sex-specific data. Additionally, cohort studies stratifying participants by quantity of alcohol intake were integrated in a dose-response analysis.

RESULTS

52 studies were included, totaling 63,707 PD patients and 9,817,924 controls. Our meta-analysis supported a statistically significant overrepresentation of never drinkers among PD subjects; odds ratio (OR) for ever drinking alcohol 0.84 (95% confidence interval (CI) 0.76 - 0.92). A subgroup analysis revealed similar effect estimates in females and males. A further synthesis of seven cohort studies suggested a negative, dose-dependent association between alcohol and risk of PD.

CONCLUSION

In the absence of a known neuroprotective pathway, there may be reason to doubt a true biological effect. The role of survivor bias, selection and recall bias, misclassification, and residual confounding requires consideration. Alternatively, observations might be attributable to reverse causation if those predestined for PD alter their alcohol habits during the preclinical phase. Major limitations of our study include high between-study heterogeneity (I2 = 93.2%) and lack of adjustment for key confounders, namely smoking status.

Parkinson's Disease Risk and Alcohol Intake: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies

Background: The association between Parkinson's disease (PD) risk and alcohol intake is a controversial topic.

Objectives: To systematically assess the association between PD risk and alcohol intake.

Methods: PubMed and Embase databases were searched for eligible studies with prospective design on PD risk and alcohol intake. A meta-analysis with a random-effects model and dose-response analysis was performed. Relative risk ratios (RRs) with 95% CIs were calculated.

Results: Eleven prospective studies were included. Overall, a higher intake of alcohol was inversely associated with PD risk (RR: 0.81, 95% CI: 0.70–0.95, I² = 73.7%). Significant differences existed between the specific types of alcoholic beverages and geographic area. Specifically, a significant association existed for beer (RR: 0.78, 95% CI: 0.65–0.94, I² = 0.0%) and studies conducted in Asia (RR: 0.66, 95% CI: 0.55–0.80, I² = 37.3%). Dose-response analysis indicated a nonlinear relationship between PD risk and alcohol exposure. No evidence for publication bias was detected.

Conclusions: In summary, our meta-analysis suggests that alcohol consumption was associated with a decreased risk of PD, with a nearly U-shaped association. Future studies are warranted to clarify the question of a specific type of alcoholic beverage-dependent association, geographic area effect, and possible threshold effects regarding both the adverse and beneficial effects of alcohol.

Age at Onset of Parkinson's Disease Among Ashkenazi Jewish Patients: Contribution of Environmental Factors, LRRK2 p.G2019S and GBA p.N370S Mutations

BACKGROUND

Both genetic and environmental factors contribute to Parkinson's disease (PD) risk.

OBJECTIVE

We investigated the potential association of several relevant variables with PD age at onset (AAO), focusing on LRRK2 p.G2019S and GBA p.N370S mutations.

METHODS

Ashkenazi Jewish (AJ) PD patients, screened for LRRK2 and GBA mutations, underwent an interview regarding exposure to the following environmental and lifestyle factors: cigarette smoking, consumption of coffee, tea and alcohol, head injury and rural living. Multivariate linear regression (adjusted for sex) was used to examine the association with AAO, and models included LRRK2 p.G2019S and GBA p.N370S mutation status (carrier/non-carriers), single environmental variable and their interactions terms, as independent variables.

RESULTS

225 Israeli AJ PD patients were enrolled: 65 LRRK2 p.G2019S mutation carriers, 60 GBA p.N370S carriers and 100 non-carries of these mutations. In the dichotomized exposure/non-exposure analyses, positive LRRK2 p.G2019S status was associated with younger AAO in all models, at nominal or near significant levels (p = 0.033-0.082). Smoking was associated with older AAO (p = 0.032), and the interaction between GBA p.N370S and history of head injury was associated with younger AAO (p = 0.049), both at nominal significance. There was no indication of a consistent main effect for GBA p.N370S status or significant LRRK2 p.G2019S-environmental factor interaction. In the dose-dependent analyses, increased coffee and tea consumption levels were associated with older AAO (p = 0.001 and p = 0.002, respectively).

CONCLUSIONS

Our results suggest that genetic and environmental factors may affect AAO in PD patients, but validation in additional samples is required.

Istradefylline to Treat Patients with Parkinson's Disease Experiencing "Off" Episodes: A Comprehensive Review

Parkinson’s disease (PD) is a common neurodegenerative disorder that leads to significant morbidity and disability. PD is caused by a loss of dopaminergic, cholinergic, serotonergic, and noradrenergic neurons in the central nervous system (CNS), and peripherally; the syndromic parkinsonism symptoms of movement disorder, gait disorder, rigidity and tremor are mostly driven by the loss of these neurons in the basal ganglia. Unfortunately, a significant proportion of patients taking levodopa, the standard of care treatment for PD, will begin to experience a decrease in effectiveness at varying times. These periods, referred to as “off episodes”, are characterized by increased symptoms and have a detrimental effect on quality of life and disability. Istradefylline, a novel adenosine A2A receptor antagonist, is indicated as a treatment addition to levodopa/carbidopa in patients experiencing “off episodes”. It promotes dopaminergic activity by antagonizing adenosine in the basal ganglia. This review will discuss istradefylline as a treatment for PD patients with off episodes.

The Links between Parkinson's Disease and Cancer

Epidemiologic studies indicate a decreased incidence of most cancer types in Parkinson’s disease (PD) patients. However, some neoplasms are associated with a higher risk of occurrence in PD patients. Both pathologies share some common biological pathways. Although the etiologies of PD and cancer are multifactorial, some factors associated with PD, such as α-synuclein aggregation; mutations of PINK1, PARKIN, and DJ-1; mitochondrial dysfunction; and oxidative stress can also be involved in cancer proliferation or cancer suppression. The main protein associated with PD, i.e., α-synuclein, can be involved in some types of neoplastic formations. On the other hand, however, its downregulation has been found in the other cancers. PINK1 can act as oncogenic or a tumor suppressor. PARKIN dysfunction may lead to some cancers’ growth, and its expression may be associated with some tumors’ suppression. DJ-1 mutation is involved in PD pathogenesis, but its increased expression was found in some neoplasms, such as melanoma or breast, lung, colorectal, uterine, hepatocellular, and nasopharyngeal cancers. Both mitochondrial dysfunction and oxidative stress are involved in PD and cancer development. The aim of this review is to summarize the possible associations between PD and carcinogenesis.

Transgenerational transduction of MPTP-induced alterations in a Parkinson's disease mouse model

Susceptibility to Parkinson's disease (PD) increases more than threefold in first-degree relatives of PD patients. Using a mouse model, we investigated in a proof-of-principle approach whether toxin exposure of F0 affects the F1 generation. We provide first evidence that disturbance of the nigrostriatal pathway can be transferred to the next generation.

Parkinson's Disease in the Middle East, North Africa, and South Asia: Consensus from the International Parkinson and Movement Disorder Society Task Force for the Middle East

BACKGROUND

Understanding the regional needs and available healthcare resources to treat Parkinson's disease (PD) is essential to plan appropriate future priorities. The International Parkinson and Movement Disorder Society (MDS) Task Force for the Middle East was established to raise awareness and promote education across the region on PD and other movement disorders. Broadly, the task force encompasses the countries of the Middle East but has included North Africa and South Asia as well (MENASA).

OBJECTIVE

To create a list of needs and priorities in the advancement of PD in MENASA countries based on consensuses generated by the MDS task force for the Middle East.

METHODS

A Strengths Weaknesses-Opportunities-Threats (SWOT) analysis was conducted by the task force members to generate consensus about PD care this region.

RESULTS

Eight overarching principles emerged for the consensus statement on current needs: more movement disorders specialists, multidisciplinary care, accurate epidemiologic data, educational programs, availability of drugs, and availability of more advanced therapy, enhanced health care resources and infrastructure, and greater levels of awareness within the general population and among health care professionals.

CONCLUSION

This pilot study sheds light on unmet needs for providing care to people with PD in the MENASA region. These data offer directions on priorities to increase awareness of PD, to develop better infrastructure for research and management of PD, to foster healthcare policy discussions for PD and to provide educational opportunities within these countries.

Caffeine Consumption through Coffee: Content in the Beverage, Metabolism, Health Benefits and Risks

Caffeine (1,3,7-trimethylxanthine) is the most consumed psychoactive substance in the world, acting by means of antagonism to adenosine receptors, mainly A1 and A2A. Coffee is the main natural source of the alkaloid which is quite soluble and well extracted during the brew’s preparation. After consumption, caffeine is almost completely absorbed and extensively metabolized in the liver by phase I (cytochrome P450) enzymes, mainly CYP1A2, which appears to be polymorphically distributed in human populations. Paraxanthine is the major caffeine metabolite in plasma, while methylated xanthines and methyluric acids are the main metabolites excreted in urine. In addition to stimulating the central nervous system, caffeine exerts positive effects in the body, often in association with other substances, contributing to prevention of several chronic diseases. The potential adverse effects of caffeine have also been extensively studied in animal species and in humans. These aspects will be approached in the present review.

Association of Two Polymorphisms in CCL2 With Parkinson's Disease: A Case-Control Study

Background: Parkinson's disease (PD) is the most common neurodegenerative movement disorder that is known to be related to neuro-inflammation. Chemokines participate in this process usually through upregulation of expression levels, which are closely related to the polymorphisms in their genes. Recent studies have further revealed the association between these polymorphisms and the risk of PD in multiple populations, but not the Chinese Han population. Methods:The promoter region of CCL2 was sequenced in 411 PD patients and 422 gender-age matched control from a Chinese Han population using PCR-RFLP method. Their genotype frequencies were analyzed statistically. Dual-luciferase reporter assays were conducted in neuroblastoma cells to assess the promoter transcriptional activity of the rs1024611 variants (T>C) and the GRCh38.p12chr17:34252593 G>C alleles in CCL2. Results:We found that the frequency of the CCL2 genotype of rs1024611 was significantly different between the PD and control groups (p = 0.021), while the C allele was associated with a significantly increased risk in the PD group (p = 0.004). Moreover, C allele of this newly identified alteration in CCL2 (GRCh38.p12chr17:34252593 G>C) was also found to be associated with an increased risk of PD (P genotype = 0.006, P allele = 0.006). Dual-luciferase reporter assay results indicated that rs1024611 C allele and GRCh38.p12chr17:.34252593 C allele increased the transcriptional activity of the CCL2 promoter. Conclusions: We, for the first time, report a risk polymorphism (rs1024611) and a new locus (GRCh38.p12chr17:.34252593 G>C) on CCL2, both of which are suggested as risk factors for PD in a Chinese Han population.

Cancers Preceding Parkinson's Disease after Adjustment for Bias in a Danish Population-Based Case-Control Study

Cancer patients are at lower risk of developing Parkinson's disease (PD) compared with the general population. One explanation is the negative association between smoking and PD, but PD risk is also lower for cancers not related to smoking. Another explanation is survival bias where death from cancer may act as a competing risk. We conducted a large population-based case-control study in Denmark and investigated whether cancer diagnosis reduced the risk of developing PD even after adjusting for important risk factors including smoking, physical activity, and lifetime oestrogen status. Using probabilistic bias analysis we quantified the influence of survival bias. We estimated negative point estimates (ORs) between cancers and PD for all cancers except skin, female breast, and ill-defined and unspecified 0.85 (95% CI 0.59-1.21); smoking-related cancers 0.75 (95% CI 0.45-1.23); and cancers not related to smoking 0.82 (95% CI 0.49-1.38) that are very similar to those previously reported for a much larger Danish register only based study, even though our confidence intervals include the null. These effect estimates shifted towards the null after accounting for survival bias but most bias-adjusted ORs remained below 1 within the range of priors considered in simulations. Overall, cancer patients have a lower risk of developing PD even after controlling for cancer-related lifestyles factors and correcting for survival bias.

Nicotine promotes neuron survival and partially protects from Parkinson's disease by suppressing SIRT6

Parkinson’s disease is characterized by progressive death of dopaminergic neurons, leading to motor and cognitive dysfunction. Epidemiological studies consistently show that the use of tobacco reduces the risk of Parkinson’s. We report that nicotine reduces the abundance of SIRT6 in neuronal culture and brain tissue. We find that reduction of SIRT6 is partly responsible for neuroprotection afforded by nicotine. Additionally, SIRT6 abundance is greater in Parkinson’s patient brains, and decreased in the brains of tobacco users. We also identify SNPs that promote SIRT6 expression and simultaneously associate with an increased risk of Parkinson’s. Furthermore, brain-specific SIRT6 knockout mice are protected from MPTP-induced Parkinson’s, while SIRT6 overexpressing mice develop more severe pathology. Our data suggest that SIRT6 plays a pathogenic and pro-inflammatory role in Parkinson’s and that nicotine can provide neuroprotection by accelerating its degradation. Inhibition of SIRT6 may be a promising strategy to ameliorate Parkinson’s and neurodegeneration.

Alcohol consumption and risk for Parkinson's disease: a systematic review and meta-analysis

The possibility that alcohol consumption should be considered as a "protective factor" for Parkinson's disease (PD) has been suggested by several case-control studies. However, other case-control studies and data from prospective longitudinal cohort studies have been inconclusive. We carried out a systematic review which included all the eligible studies published on PD risk related with alcohol consumption, and conducted a meta-analysis according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The systematic review was performed using two databases, and the meta-analysis of the eligible studies with the software Meta-Disc1.1.1. Heterogeneity between studies was tested with the Q-statistic. The meta-analysis included 26 eligible retrospective case-control studies (8798 PD patients, 15,699 controls) and 5 prospective longitudinal cohort studies (2404 PD patients, 600,592 controls) on alcohol consumption and PD. In retrospective case-control studies the frequency of PD patients never drinkers was higher and the frequency of heavy + moderate drinkers was lower [diagnostic OR (95% CI) 1.33(1.20-1.48) and 0.74(0.64-0.85)], respectively, when compared to healthy controls. In contrast, in prospective studies, the differences were not significant with the exception of a trend towards a higher frequency of non-drinkers in PD women and a significantly lower frequency of moderate + heavy drinkers in PD men in those studies which stratified data by gender. The present meta-analysis suggests an inverse association between alcohol consumption and PD, which is supported by the results of case-control studies but not clearly by prospective ones.

Epidemiology of Parkinson's Disease-East Versus West

Background

The cause of PD at present remains unknown. A number of epidemiological studies have been conducted across the globe to ascertain the disease burden and the possible risk factors. In this review, we analyze the various studies from East and West with an aim to observe the important similarities and differences in the disease occurrence and risk factor profile.

Methods

A comprehensive search of descriptive and analytical epidemiological studies was undertaken. The descriptive studies and meta-analysis providing the standardised population rates were selected. The demographics, ethnicity and geographical differences between East and West were analysed. In analytical epidemiology, more established and well-studied non-genetic risk factors for PD were reviewed utilising the prospective cohort studies, case control studies and meta-analysis where available.

Results and Conclusion

PD is more common with increasing age and shows male predominance, which is more obvious in Western studies. The PD prevalence and incidence rates are slightly lower in the East compared to the West. Incidence studies on different ethnic populations in the same country have also found a lower occurrence of PD amongst Easterners compared to Westerners. Setting methodological differences aside, studies from East and West suggest a role for both environmental and genetic risk factors in PD causation. Smoking, caffeine intake and pesticide exposure are well-established risk factors across regions. There is a robust data for dairy product consumption, urate levels and physical activity in the West while studies on certain risk factors like head injury and alcohol show conflicting and mixed results.

Pooled analysis of the HLA-DRB1 by smoking interaction in Parkinson disease

OBJECTIVE

Inflammatory response plays an important role in Parkinson disease (PD). Previous studies have reported an association between human leukocyte antigen (HLA)-DRB1 and the risk of PD. There has also been growing interest in investigating whether inflammation-related genes interact with environmental factors such as smoking to influence PD risk. We performed a pooled analysis of the interaction between HLA-DRB1 and smoking in PD in 3 population-based case-control studies from Denmark and France.

METHODS

We included 2,056 cases and 2,723 controls from 3 PD studies (Denmark, France) that obtained information on smoking through interviews. Genotyping of the rs660895 polymorphism in the HLA-DRB1 region was based on saliva or blood DNA samples. To assess interactions, we used logistic regression with product terms between rs660895 and smoking. We performed random-effects meta-analysis of marginal associations and interactions.

RESULTS

Both carrying rs660895-G (AG vs AA: odds ratio [OR] = 0.81; GG vs AA: OR = 0.56; p-trend = 0.003) and ever smoking (OR = 0.56, p < 0.001) were inversely associated with PD. A multiplicative interaction was observed between rs660895 and smoking using codominant, additive (interaction parameter = 1.37, p = 0.005), and dominant (interaction parameter = 1.54, p = 0.001) genetic models without any heterogeneity (I² = 0.0%); the inverse association of rs660895-(AG+GG) with PD seen in never smokers (OR = 0.64, p < 0.001) disappeared among ever smokers (OR = 1.00, p = 0.99). Similar interactions were observed when we investigated light and heavy smokers separately.

INTERPRETATION

Our study provides the first evidence that smoking modifies the previously reported inverse association of rs660895-G with PD, and suggests that smoking and HLA-DRB1 are involved in common pathways, possibly related to neuroinflammation. Ann Neurol 2017;82:655-664.

Nicotine from cigarette smoking and diet and Parkinson disease: a review

Evidence from epidemiological studies suggest a relationship between cigarette smoking and low risk of Parkinson disease (PD). As a major component of tobacco smoke, nicotine has been proposed to be a substance for preventing against PD risk, with a key role in regulating striatal activity and behaviors mediated through the dopaminergic system. Animal studies also showed that nicotine could modulate dopamine transmission and reduce levodopa-induced dyskinesias. However, previous clinical trials yield controversial results regarding nicotine treatment. In this review, we updated epidemiological, preclinical and clinical data, and studies on nicotine from diet. We also reviewed interactions between genetic factors and cigarette smoking. As a small amount of nicotine can saturate a substantial portion of nicotine receptors in the brain, nicotine from other sources, such as diet, could be a promising therapeutic substance for protection against PD.

Tobacco Use, Oral Health, and Risk of Parkinson's Disease

Few studies have investigated the associations between use of Swedish moist snuff (snus), associated poor oral health, and risk of Parkinson's disease (PD). We followed 20,175 participants who were free of PD in 1973-1974 in Uppsala, Sweden, until the end of 2012. We used Cox proportional hazards regression models to estimate hazard ratios and corresponding 95% confidence intervals for the associations between tobacco use, oral health indicators, and PD risk. We found that tobacco use was associated with a lower risk of PD in males. Compared with males who never used any tobacco daily, pure ever tobacco smokers, pure ever snus users, and combined users had adjusted hazard ratios of 0.68 (95% confidence interval (CI): 0.49, 0.93; n = 83), 0.51 (95% CI: 0.27, 0.95; n = 11), and 0.21 (95% CI: 0.07, 0.67; n = 3), respectively. No association was observed for number of teeth, dental plaque, or detectable oral mucosal lesions and PD risk, although there was a suggestive association with Candida-related oral mucosal lesions in males (hazard ratio = 1.56, 95% CI: 0.92, 2.65; P = 0.098). Use of snus is associated with a lower risk of PD in males, while poor oral health seems not to be associated with PD occurrence.

Gene-Environment Interaction in Parkinson's Disease: Coffee, ADORA2A, and CYP1A2

BACKGROUND AND PURPOSE

Drinking caffeinated coffee has been reported to provide protection against Parkinson's disease (PD). Caffeine is an adenosine A2A receptor (encoded by the gene ADORA2A) antagonist that increases dopaminergic neurotransmission and Cytochrome P450 1A2 (gene: CYP1A2) metabolizes caffeine; thus, gene polymorphisms in ADORA2A and CYP1A2 may influence the effect coffee consumption has on PD risk.

METHODS

In a population-based case-control study (PASIDA) in Denmark (1,556 PD patients and 1,606 birth year- and gender-matched controls), we assessed interactions between lifetime coffee consumption and 3 polymorphisms in ADORA2A and CYP1A2 for all subjects, and incident and prevalent PD cases separately using logistic regression models. We also conducted a meta-analysis combining our results with those from previous studies.

RESULTS

We estimated statistically significant interactions for ADORA2A rs5760423 and heavy vs. light coffee consumption in incident (OR interaction = 0.66 [95% CI 0.46-0.94], p = 0.02) but not prevalent PD. We did not observe interactions for CYP1A2 rs762551 and rs2472304 in incident or prevalent PD. In meta-analyses, PD associations with daily coffee consumption were strongest among carriers of variant alleles in both ADORA2A and CYP1A2.

CONCLUSION

We corroborated results from a previous report that described interactions between ADORA2A and CYP1A2 polymorphisms and coffee consumption. Our results also suggest that survivor bias may affect results of studies that enroll prevalent PD cases.

The associations between Parkinson's disease and cancer: the plot thickens

Epidemiological studies support a general inverse association between the risk of cancer development and Parkinson’s disease (PD). In recent years however, increasing amount of eclectic evidence points to a positive association between PD and cancers through different temporal analyses and ethnic groups. This positive association has been supported by several common genetic mutations in SNCA, PARK2, PARK8, ATM, p53, PTEN, and MC1R resulting in cellular changes such as mitochondrial dysfunction, aberrant protein aggregation, and cell cycle dysregulation. Here, we review the epidemiological and biological advances of the past decade in the association between PD and cancers to offer insight on the recent and sometimes contradictory findings.