Association between Parkinson's Disease and Cancer: New Findings and Possible Mediators.

Epidemiological evidence points to an inverse association between Parkinson's disease (PD) and almost all cancers except melanoma, for which this association is positive. The results of multiple studies have demonstrated that patients with PD are at reduced risk for the majority of neoplasms. Several potential biological explanations exist for the inverse relationship between cancer and PD. Recent results identified several PD-associated proteins and factors mediating cancer development and cancer-associated factors affecting PD. Accumulating data point to the role of genetic traits, members of the synuclein family, neurotrophic factors, the ubiquitin-proteasome system, circulating melatonin, and transcription factors as mediators. Here, we present recent data about shared pathogenetic factors and mediators that might be involved in the association between these two diseases. We discuss how these factors, individually or in combination, may be involved in pathology, serve as links between PD and cancer, and affect the prevalence of these disorders. Identification of these factors and investigation of their mechanisms of action would lead to the discovery of new targets for the treatment of both diseases.

Blood-based biological ageing and red cell distribution width are associated with prevalent Parkinson's disease: findings from a large Italian population cohort.

Background: Aging clocks tag the actual underlying age of an organism and its discrepancy with chronological age and have been reported to predict incident disease risk in the general population. However, the relationship with neurodegenerative risk and in particular with Parkinson's Disease (PD) remains unclear, with few discordant findings reporting associations with both incident and prevalent PD risk. Objective: To clarify this relationship, we computed a common aging clock based on blood markers and tested the resulting discrepancy with chronological age (ΔPhenoAge) for association with both incident and prevalent PD risk. Methods: In a large Italian population cohort - the Moli-sani study (N=23,437; age ≥ 35 years; 52% women) - we carried out both Cox Proportional Hazards regressions modelling ΔPhenoAge as exposure and incident PD as outcome, and linear models testing prevalent PD as exposure and ΔPhenoAge as outcome. All models were incrementally adjusted for age, sex, education level completed and other risk/protective factors previously associated with PD risk in the same cohort (prevalent dysthyroidism, hypertension, diabetes, use of oral contraceptives, exposure to paints, daily coffee intake and cigarette smoking). Results: No significant association between incident PD risk (209 cases, median (IQR) follow-up time 11.19 (2.03) years) and PhenoAging was observed (Hazard Ratio [95% Confidence Interval] = 0.98 [0.71; 1.37]). However, a small but significant increase of ΔPhenoAge was observed in prevalent PD cases vs healthy subjects (ß (Standard Error) = 1.39 (0.70)). An analysis of each component biomarker of PhenoAge revealed a significant positive association of prevalent PD status with red cell distribution width (RDW; ß (SE) = 0.46 (0.18)). All the remaining markers did not show any significant evidence of association. Conclusion: The reported evidence highlights systemic effects of prevalent PD status on biological aging and red cell distribution width. Further cohort and functional studies may help shedding a light on the related pathways altered at the organism level in prevalent PD, like red cells variability, inflammatory and oxidative stress mechanisms.

Long-term exposure to major constituents of fine particulate matter and neurodegenerative diseases: A population-based survey in the Pearl River Delta Region, China.

BACKGROUND: Exposure to PM2.5 has been linked to neurodegenerative diseases, with limited understanding of constituent-specific contributions. OBJECTIVES: To explore the associations between long-term exposure to PM2.5 constituents and neurodegenerative diseases. METHODS: We recruited 148,274 individuals aged ≥ 60 from four cities in the Pearl River Delta region, China (2020 to 2021). We calculated twenty-year average air pollutant concentrations (PM2.5 mass, black carbon (BC), organic matter (OM), ammonium (NH4+), nitrate (NO3-) and sulfate (SO42-)) at the individuals' home addresses. Neurodegenerative diseases were determined by self-reported doctor-diagnosed Alzheimer's disease (AD) and Parkinson's disease (PD). Generalized linear mixed models were employed to explore associations between pollutants and neurodegenerative disease prevalence. RESULTS: PM2.5 and all five constituents were significantly associated with a higher prevalence of AD and PD. The observed associations generally exhibited a non-linear pattern. For example, compared with the lowest quartile, higher quartiles of BC were associated with greater odds for AD prevalence (i.e., the adjusted odds ratios were 1.81; 95% CI, 1.45-2.27; 1.78; 95% CI, 1.37-2.32; and 1.99; 95% CI, 1.54-2.57 for the second, third, and fourth quartiles, respectively). CONCLUSIONS: Long-term exposure to PM2.5 and its constituents, particularly combustion-related BC, OM, and SO42-, was significantly associated with higher prevalence of AD and PD in Chinese individuals. ENVIRONMENTAL IMPLICATION: PM2.5 is a routinely regulated mixture of multiple hazardous constituents that can lead to diverse adverse health outcomes. However, current evidence on the specific contributions of PM2.5 constituents to health effects is scarce. This study firstly investigated the association between PM2.5 constituents and neurodegenerative diseases in the moderately to highly polluted Pearl River Delta region in China, and identified hazardous constituents within PM2.5 that have significant impacts. This study provides important implications for the development of targeted PM2.5 prevention and control policies to reduce specific hazardous PM2.5 constituents.

Association of antihypertensives and Parkinson's disease in a primary care population matched for underlying diagnosis.

PURPOSE: To examine the association of several antihypertensive medication classes with incidence of Parkinson's disease (PD), taking into account possible underlying conditions. METHODS: In a case-control study based on a large primary care database and including 21,981 PD cases and 21,981 non-PD controls matched for age, sex, and possible treatment indications associations with different antihypertensive medication groups, including diuretics, betablockers, calcium channel blockers, angiotensin-converting enzyme inhibitors and angiotensin-II receptor-blockers and PD were examined. RESULTS: Antihypertensive medications overall were associated with a lower risk of subsequent diagnosis of PD (OR: 0.94, 95% CI 0.90-0.97), with the negative association most significant for medications acting on the renin-angiotensin-aldosterone system. A positive association with diagnosis of PD was only seen for betablockers and restricted to those with relatively young age and not in those with longer treatment duration. CONCLUSION: When taking into account underlying diagnoses, antihypertensive medications overall were associated with a reduced incidence of PD.

Darier disease is associated with neurodegenerative disorders and epilepsy.

Darier disease (DD) is a rare monogenetic skin disorder with limited data on its potential association with neurological disorders. This study aimed to investigate the association between DD and neurological disorders, specifically Parkinson's disease, dementias, and epilepsy. Using Swedish national registers in a period spanning between 1977 and 2013, 935 individuals with DD were compared with up to 100 comparison individuals each, randomly selected from the general population based on birth year, sex, and county of residence at the time of the first diagnosis of DD. Individuals with DD had increased risks of being diagnosed with Parkinson's disease (RR 2.1, CI 1.1; 4.4), vascular dementia (RR 2.1, CI 1.0; 4.2), and epilepsy, (RR 2.5, CI 1.8; 3.5). No association of DD with other dementias were detected. This study demonstrates a new association between DD and neurodegenerative disorders and epilepsy, underlining the need for increased awareness, interdisciplinary collaboration, and further research to understand the underlying mechanisms. Early identification and management of neurological complications in DD patients could improve treatment strategies and patient outcomes. The findings also highlight the role of SERCA2 in the pathophysiology of neurological disorders, offering new targets for future research and potentials for novel treatments.

Delirium is more common and associated with worse outcomes in Parkinson's disease compared to older adult controls: results of two prospective longitudinal cohort studies.

BACKGROUND: Inpatient prevalence of Parkinson's disease (PD) delirium varies widely across the literature. Delirium in general older populations is associated with adverse outcomes, such as increased mortality, dementia, and institutionalisation. However, to date there are no comprehensive prospective studies in PD delirium. This study aimed to determine delirium prevalence in hospitalised PD participants and the association with adverse outcomes, compared to a control group of older adults without PD. METHODS: Participants were hospitalised inpatients from the 'Defining Delirium and its Impact in Parkinson's Disease' and the 'Delirium and Cognitive Impact in Dementia' studies comprising 121 PD participants and 199 older adult controls. Delirium was diagnosed prospectively using the Diagnostic and Statistical Manual of Mental Disorders 5th Edition criteria. Outcomes were determined by medical note reviews and/or home visits 12 months post hospital discharge. RESULTS: Delirium was identified in 66.9% of PD participants compared to 38.7% of controls (p < 0.001). In PD participants only, delirium was associated with a significantly higher risk of mortality (HR = 3.3 (95% confidence interval [CI] = 1.3-8.6), p = 0.014) and institutionalisation (OR = 10.7 (95% CI = 2.1-54.6), p = 0.004) 12 months post-discharge, compared to older adult controls. However, delirium was associated with an increased risk of developing dementia 12 months post-discharge in both PD participants (OR = 6.1 (95% CI = 1.3-29.5), p = 0.024) and in controls (OR = 13.4 (95% CI = 2.5-72.6), p = 0.003). CONCLUSION: Delirium is common in hospitalised PD patients, affecting two thirds of patients, and is associated with increased mortality, institutionalisation, and dementia. Further research is essential to understand how to accurately identify, prevent and manage delirium in people with PD who are in hospital.

An examination of anxiety and its influence on health-related quality of life in Parkinson's disease using the geriatric anxiety scale: a cross-sectional study.

BACKGROUND: Anxiety is one of the most common but often overlooked mood-related nonmotor symptoms in people with Parkinson's disease (PD). To improve the well-being of people with PD, it is important to understand the impact of anxiety in PD, especially its association with depressive and motor symptoms and its impact on health-related quality of life (HRQoL). METHODS: 91 people with PD were assessed between June 2017 and June 2018. Anxiety was measured using the Geriatric Anxiety Scale (GAS) and its cognitive, somatic, and affective subscales. HRQoL was assessed using the Parkinson's Disease Questionnaire 39 (PDQ-39). Moreover, sociodemographic information, depressive symptoms, cognition, motor and nonmotor symptoms were assessed. Descriptive statistics, regression analyses, and path analyses were performed to understand predictors of anxiety and its influence on HRQoL. RESULTS: Of the 91 people with PD, 35 (38.5%) experienced anxiety. Anxiety symptoms in these individuals primarily manifest as somatic sensations. Anxiety, motor, and depressive symptoms are interlinked but contribute individually to HRQoL. Beyond motor symptoms, cognitive and affective aspects of anxiety impact HRQoL. While anxiety and depression overlap, the somatic and cognitive aspects of anxiety play a significant role in determining HRQoL in addition to depressive symptoms. CONCLUSION: Our study used the GAS and its three subscales to shed light on the connections between anxiety, depression, and motor impairment in people with PD. Although anxiety is linked to depression and motor symptoms, it independently affects the HRQoL of people with PD. Thus, it is crucial to adopt a comprehensive diagnostic approach that detects and considers the impact of anxiety on HRQoL in PD.

Covid-19 in Parkinson's Disease treated by drugs or brain stimulation.

PURPOSE: Covid-19 has affected all people, especially those with chronic diseases, including Parkinson's Disease (PD). Covid-19 may affect both motor and neuropsychiatric symptoms of PD patients. We intend to evaluate different aspects of Covid-19 impact on PD patients. METHODS: 647 PD patients were evaluated in terms of PD-related and Covid-19-related clinical presentations in addition to past medical history during the pandemic through an online questioner. They were compared with an age-matched control group consist of 673 individuals and a sample of the normal population consist of 1215 individuals. RESULTS: The prevalence of Covid-19 in PD patients was 11.28%. The mortality was 1.23% among PD patients. The prevalence of Covid-19 in PD patients who undergone Deep Brain Stimulation (DBS) was 18.18%. No significant association was found between the duration of disease and the prevalence of Covid-19. A statistically significant higher prevalence of Covid-19 in PD patients who had direct contact with SARS-CoV-19 infected individuals was found. No statistically significant association has been found between the worsening of motor symptoms and Covid-19. PD patients and the normal population may differ in the prevalence of some psychological disorders, including anxiety and sleeping disorders, and Covid-19 may affect the psychological status. CONCLUSION: PD patients possibly follow tighter preventive protocols, which lead to lower prevalence and severity of Covid-19 and its consequences in these patients. Although it seems Covid-19 does not affect motor and psychological aspects of PD as much as it was expected, more accurate evaluations are suggested in order to clarify such effects.

Increased Risk of New-Onset Parkinson's Disease Following a Diagnosis of Retinal Vascular Occlusion: A 14-Year Cohort Study.

BACKGROUND: Although the role of the vascular component in the pathophysiology of Parkinson's disease is widely accepted and retinal vascular abnormalities are commonly observed in Parkinson's disease patients, evidence connecting retinal vascular disorders with the risk of developing Parkinson's disease is limited. We aimed to investigate the association between retinal vascular occlusion (RVO) and the risk of developing Parkinson's disease in people over 60 years using a nationwide cohort. METHODS: From the 14-year South Korean National Health Insurance Service-Senior cohort, 11 210 incident RVO patients and 11 210 propensity scores, risk-matched controls were included. The incidence of Parkinson's disease was estimated with a Poisson regression. A Cox proportional hazards regression model was used to investigate the associations between RVO and the risk of Parkinson's disease. RESULTS: The incidence of Parkinson's disease was 664.4 cases per 100 000 person-years (95% confidence interval [CI], 599.7-736.0) in the RVO cohort. Individuals with RVO had an increased incidence of Parkinson's disease (hazard ratio [HR], 1.28; 95% CI: 1.10-1.49). Increased PD risk was predominantly observed in retinal artery occlusion patients (HR, 1.53; 95% CI: 1.11-2.12), male patients (HR, 1.67; 95% CI: 1.29-2.17), and 5 years after diagnosis (HR, 1.46; 95% CI: 1.10-1.93). CONCLUSIONS: Our findings suggest that a common pathophysiological pathway, such as vasculature changes, may exist between RVO and Parkinson's disease. RVO may be one of the risk factors associated with future development of Parkinson's disease. The nature of this association warrants further investigation.

Biomarkers of Physical and Mental Health for Prediction of Parkinson's Disease: A Population-Based Study from 15 European Countries.

OBJECTIVES: Early diagnosis of Parkinson's disease (PD) is critical for optimal treatment. However, the predictive potential of physical and mental health in PD is poorly characterized. METHODS: We evaluated the potential of multiple demographic, physical, and mental factors in predicting the future onset of PD in older adults aged 50 years or older from 15 European countries. Individual study participants were followed over four waves of the Survey of Health, Ageing, and Retirement in Europe (SHARE) from 2013-2020. RESULTS: Of 57,980 study participants, 442 developed PD during the study period. We identified male sex and advancing age from the sixth decade of life onward as significant predictors of future PD. Among physical factors, a low handgrip strength (HGS; men <27 kg, women <16 kg), being bothered by frailty, and recent falls were significantly associated with future PD. Among mental factors, a higher depression (Euro-D depression score >6) emerged as an independent predictor of future PD. Finally, the presence of hypertension or Alzheimer's disease (AD) increases the risk of future PD. CONCLUSIONS: Altogether, male sex, advancing age, low HGS, frailty, depression, hypertension, and AD were identified as critical risk factors for future PD. Our results may be useful in the early identification and treatment of populations at risk for PD.

Care of Late-Stage Parkinsonism: Resource Utilization of the Disease in Five European Countries.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disease that leads to progressive disability. Cost studies have mainly explored the early stages of the disease, whereas late-stage patients are underrepresented. OBJECTIVE: The aim is to evaluate the resource utilization and costs of PD management in people with late-stage disease. METHODS: The Care of Late-Stage Parkinsonism (CLaSP) study collected economic data from patients with late-stage PD and their caregivers in five European countries (France, Germany, the Netherlands, UK, Sweden) in a range of different settings. Patients were eligible to be included if they were in Hoehn and Yahr stage >3 in the on state or Schwab and England stage at 50% or less. In total, 592 patients met the inclusion criteria and provided information on their resource utilization. Costs were calculated from a societal perspective for a 3-month period. A least absolute shrinkage and selection operator approach was utilized to identify the most influential independent variables for explaining and predicting costs. RESULTS: During the 3-month period, the costs were €20,573 (France), €19,959 (Germany), €18,319 (the Netherlands), €25,649 (Sweden), and €12,156 (UK). The main contributors across sites were formal care, hospitalization, and informal care. Gender, age, duration of the disease, Unified Parkinson's Disease Rating Scale 2, the EQ-5D-3L, and the Schwab and England Scale were identified as predictors of costs. CONCLUSION: Costs in this cohort of individuals with late-stage PD were substantially higher compared to previously published data on individuals living in earlier stages of the disease. Resource utilization in the individual sites differed in part considerably among these three parameters mentioned. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Place of death in Parkinson's disease and related disorders in England and Wales: post-pandemic trends and implications for care planning.

BACKGROUND: With growing emphasis on palliative care for neurodegenerative conditions, understanding trends in place of death helps improve quality of end-of-life care for people with Parkinson's disease and related disorders (PDRDs), focusing allocation of resources and training and identifying inequalities. OBJECTIVES: Review national and regional place of death trends for people with PDRD including pre- and post-pandemic trends. METHODS: Mortality data for England and Wales (March 2018 and July 2022) were analysed with summary statistics and interrupted time series, exploring place of death for those who died with PDRD, with and without coexisting dementia, with reference to all deaths in England and Wales. RESULTS: Of 2,415,566 adult deaths, 56,790 included mention of PDRD. Hospital deaths were most common in people with PDRD (39.17%), followed by care homes (38.84%). People with PDRD were half as likely to die in hospice compared with the general population (2.03 vs 4.94%). Proportion of care home deaths fell significantly after March 2020 (40.6-37%, P = 0.035). Regionally, London was an outlier with a lower proportion of deaths occurring in care homes with a higher proportion of hospital deaths. CONCLUSION: Place of death for people with PDRD is changing, with more hospice and home deaths. People with PDRD, particularly those with co-existent dementia, are less likely to access inpatient hospice care than the general population. Since the COVID-19 pandemic, the proportion of care home deaths has reduced significantly with an increase in home deaths, with implications for service and resource allocation.

Trafficking in Disease: More Evidence for Air Pollution-Parkinson's Association.

Research using Sister Study data has implicated nitrogen dioxide (vehicle exhaust is a major source), and possibly fine particulate matter, in increased risk for Parkinson's disease.

Causal association between long-term exposure to air pollution and incident Parkinson's disease.

Epidemiological evidence for long-term air pollution exposure and Parkinson's disease (PD) is controversial, and analysis of causality is limited. We identified 293,888 participants who were free of PD at baseline in the UK Biobank (2006-2010). Time-varying air pollution [fine particulate (PM2.5) and ozone (O3)] exposures were estimated using spatio-temporal models. Incident cases of PD were identified using validated algorithms. Four methods were used to investigate the associations between air pollution and PD, including (1) standard time-varying Cox proportional-hazard model; (2) Cox models weighted by generalized propensity score (GPS) and inverse-probability weights (IPW); (3) instrumental variable (IV) analysis; and (4) negative control outcome analysis. During a median of 11.6 years of follow-up, 1822 incident PD cases were identified. Based on standard Cox regression, the hazard ratios (95% confidence interval) for a 1 µg/m3 or ppb increase in PM2.5 and O3 were 1.23 (1.17, 1.30) and 1.02 (0.98, 1.05), respectively. Consistent results were found in models weighted by GPS and IPW, and in IV analysis. There were no significant associations between air pollution and negative control outcomes. This study provides evidence to support a causal association between PM2.5 exposure and PD. Mitigation of air pollution could be a protective measure against PD.

Causal relationships between Sjögren's syndrome and Parkinson's disease: A Mendelian randomization study.

BACKGROUND: Epidemiological and observational studies have indicated an association between Sjögren's syndrome (SS) and Parkinson's disease (PD). However, consistent conclusions have not been reached due to various limitations. In order to determine whether SS and PD are causally related, we conducted a Mendelian randomization study (MR) with two samples. METHODS: Data for SS derived from the FinnGen consortium's R9 release (2495 cases and 365 533 controls). Moreover, data for PD were acquired from the publicly available GWAS of European ancestry, which involved 33 674 cases and 449 056 controls. The inverse variance weighted, along with four other effective methodologies, were employed to comprehensively infer the causal relationships between SS and PD. To assess the estimation's robustness, a number of sensitivity studies were performed. To determine the probability of reverse causality, we performed a reverse MR analysis. RESULTS: There was no evidence of a significant causal effect of SS on PD risks based on the MR [odds ratio (OR) = 1.03; 95% confidence interval (CI) = 0.95-1.11; p = .45]. Similarly, no evidence supported the causal effects of PD on SS (OR = 0.92; 95% CI = 0.81-1.04; p = .20). These findings held up under rigorous sensitivity analysis. CONCLUSIONS: MR bidirectional analysis did not reveal any cause-and-effect relationship between SS and PD, or vice versa. Further study of the mechanisms that may underlie the probable causal association between SS and PD is needed.

Association of Coffee Consumption and Prediagnostic Caffeine Metabolites With Incident Parkinson Disease in a Population-Based Cohort.

BACKGROUND AND OBJECTIVES: Inverse associations between caffeine intake and Parkinson disease (PD) have been frequently implicated in human studies. However, no studies have quantified biomarkers of caffeine intake years before PD onset and investigated whether and which caffeine metabolites are related to PD. METHODS: Associations between self-reported total coffee consumption and future PD risk were examined in the EPIC4PD study, a prospective population-based cohort including 6 European countries. Cases with PD were identified through medical records and reviewed by expert neurologists. Hazard ratios (HRs) and 95% CIs for coffee consumption and PD incidence were estimated using Cox proportional hazards models. A case-control study nested within the EPIC4PD was conducted, recruiting cases with incident PD and matching each case with a control by age, sex, study center, and fasting status at blood collection. Caffeine metabolites were quantified by high-resolution mass spectrometry in baseline collected plasma samples. Using conditional logistic regression models, odds ratios (ORs) and 95% CIs were estimated for caffeine metabolites and PD risk. RESULTS: In the EPIC4PD cohort (comprising 184,024 individuals), the multivariable-adjusted HR comparing the highest coffee intake with nonconsumers was 0.63 (95% CI 0.46-0.88, p = 0.006). In the nested case-control study, which included 351 cases with incident PD and 351 matched controls, prediagnostic caffeine and its primary metabolites, paraxanthine and theophylline, were inversely associated with PD risk. The ORs were 0.80 (95% CI 0.67-0.95, p = 0.009), 0.82 (95% CI 0.69-0.96, p = 0.015), and 0.78 (95% CI 0.65-0.93, p = 0.005), respectively. Adjusting for smoking and alcohol consumption did not substantially change these results. DISCUSSION: This study demonstrates that the neuroprotection of coffee on PD is attributed to caffeine and its metabolites by detailed quantification of plasma caffeine and its metabolites years before diagnosis.

Unraveling the interplay between dyskinesia and overactive bladder symptoms in Parkinson's disease: a comprehensive cohort study based on the long-term follow-up database of Parkinson's disease.

OBJECTIVES: Overactive bladder (OAB) and dyskinesia are frequent complications in patients with Parkinson's disease (PD). However, the correlation between OAB and dyskinesia has been insufficiently explored. The purpose of this study was to examine the relationship between dyskinesia, OAB, and clinical characteristics among individuals with PD. METHODS: 1338 PD patients were included in the present study. Demographic features were compared between patients with or without dyskinesia and OAB symptoms. Logistic regression was conducted on dyskinesia to screen clinically relevant factors. Overactive Bladder Symptom Score (OABSS) was further used to stratify the association between the severity of OAB and the occurrence of dyskinesia. RESULTS: This study indicates that both dyskinesia and OAB are significantly related to disease severity and cognitive status. PD patients with dyskinesia and OAB having higher UPDRS scores (p < 0.001), H-Y scores (p < 0.001), NMSQ (p < 0.001) and MoCA scores (p < 0.001), and lower MMSE scores (p < 0.001) are identified. The multivariate logistic regression confirms that disease duration (p = 0.041), LEDD (p < 0.001), UPDRSII (p < 0.001), MoCA (p = 0.024), urgency (p < 0.001), frequency (p < 0.001), and nocturia (p = 0.002) are independent risk factors for dyskinesia. Trend analysis indicates that the risk of dyskinesia significantly increases when patients exhibit moderate to severe OAB symptoms (OABSS > 5) (p < 0.001). No significant interactions were found between OABSS and age, gender, disease duration, LEDD, and NMSQ scores in different subgroups, indicating that dyskinesia is more pronounced in patients with OABSS > 5. DISCUSSION: This study provides compelling evidence supporting the strong correlation between OAB and dyskinesia in PD patients, emphasizing the presence of shared pathogenic mechanisms between these two conditions. Our findings underscore the importance of considering both OAB and dyskinesia in the clinical management of PD, investigating the intricate connections between OAB and dyskinesia could unveil valuable insights into the complex pathophysiology of PD and potentially identify novel therapeutic targets for more effective PD treatment strategies.

Causal association between atopic dermatitis and Parkinson's disease: A bidirectional Mendelian randomization study.

BACKGROUND: Atopic dermatitis is one of the most common skin disorders. Evidence has suggested an association between skin disorders, such as atopic dermatitis, and Parkinson's disease (PD). However, whether atopic dermatitis has a causal effect on PD remains unknown. METHODS: The study aimed to determine whether their association between atopic dermatitis and PD is causal, using a bidirectional two-sample Mendelian randomization method. Genetic variants from the public genome-wide association studies for atopic dermatitis (n = 10788 cases and 30047 controls) were selected to evaluate their causal effects on the risk of PD (33,674 cases and 449,056 controls). The inverse variance weighted (IVW) method was used as the primary analysis. RESULTS: The IVW results indicated that atopic dermatitis was associated with decreased risk of PD {fixed effects: odds ratio [OR] [95% confidence interval (CI)]: .905 [.832-.986], p = .022; OR [95% CI]: .905 [.827-.991], p = .032}. However, we failed to detect the causal effects of PD on risk of atopic dermatitis in the reverse causation analysis. CONCLUSION: This study indicated causal association of genetically proxied atopic dermatitis with the risk of PD. Future studies are warranted to explore the underlying mechanism and investigate the targeting effect of atopic dermatitis on PD.