Decreased Risk of Parkinson's Disease After Rheumatoid Arthritis Diagnosis: A Nested Case-Control Study with Matched Cases and Controls

Association of Autoimmune Diseases with the Risk of Parkinson's Disease

INTRODUCTION

PD is a progressive neurodegeneration disease characterized by cardinal motor symptoms such as bradykinesia and tremor. The pathogenesis of PD remains unclear. It is hypothesized that immune system dysfunction may contribute to PD. Thus, autoimmune diseases may influence the risk of incident PD.

METHODS

We included 398,329 participants without PD at the baseline from UK Biobank. The association between 20 autoimmune diseases with PD was examined using cox hazards regression analyses, adjusting covariates like age, sex, and smoking status in the statistical models. Sensitivity analyses were conducted, adjusting for polygenic risk score and the reported source of PD, to check the robustness.

RESULTS

After an average follow-up of 13.1 ± 0.816 years, 2,245 participants were diagnosed with incident PD. After multiple comparison correction, only multiple sclerosis (MS) reached statistical significance and showed an increased risk for incident PD. Compared with non-MS patients, the risk of incident PD in MS patients was 2.57-fold with age and sex being adjusted (95% CI, 1.59-4.14; adjust p value = 0.002). After adjusting lifestyle and other factors, the hazard ratio of incident PD in MS patients was 2.49 (95% CI, 1.55-4.02; adjust p value = 0.004). Excluding the self-reported PD cases in the sensitivity analysis, MS was a detrimental factor for incident PD (HR, 2.06; 95% CI, 1.56-4.05; adjust p value = 0.004). The link between MS and PD did not reach the statistical significance in the sensitivity analysis adjusting the PRS (adjust p value = 0.95).

CONCLUSION

Our study provided evidence from observational analyses that MS was associated with an increased risk of PD. Further investigations should be performed to determine the causal association and potential pathophysiology between MS and PD.

Sjögren's syndrome and Parkinson's Disease: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Previous observational studies have reported an association between Sjögren's syndrome (SS) and an increased risk of Parkinson's Disease (PD). However, the causal relationship between these conditions remains unclear. The objective of this study was to investigate the causal impact of SS on the risk of developing PD, utilizing the Mendelian randomization (MR) approach.

METHODS

We conducted a bidirectional MR analysis using publicly available genome-wide association studies (GWAS) data. The primary analysis utilized the inverse-variance weighted (IVW) method. Complementary methods, such as MR-Egger regression, weighted mode, weighted median, and MR-pleiotropy residual sum and outlier (MR-PRESSO), were utilized to identify and correct for the presence of horizontal pleiotropy.

RESULTS

The IVW MR analysis revealed no significant association between SS and PD (IVW: OR = 1.00, 95% CI = 0.94-1.07, P = 0.95). Likewise, the reverse MR analysis did not identify any significant causal relationship between PD and SS (IVW: OR = 0.98, 95% CI = 0.85-1.12, P = 0.73). The results from MR-Egger regression, weighted median, and weighted mode approaches were consistent with the IVW method. Sensitivity analyses suggested that horizontal pleiotropy is unlikely to introduce bias to the causal estimates.

CONCLUSION

This study does not provide evidence to support the assertion that SS has a conclusive impact on the risk of PD, which contradicts numerous existing observational reports. Further investigation is necessary to determine the possible mechanisms behind the associations observed in these observational studies.

Rheumatoid Arthritis and Risk of Parkinson Disease in Korea

Importance

Although it has been postulated that chronic inflammation caused by rheumatoid arthritis (RA) contributes to the development of Parkinson disease (PD), the association between these 2 conditions has yet to be determined.

Objective

To evaluate the association between RA and subsequent PD risk.

Design, Setting, and Participants

This retrospective cohort study used the Korean National Health Insurance Service database to collect population-based, nationally representative data on patients with RA enrolled from 2010 to 2017 and followed up until 2019 (median follow-up, 4.3 [IQR, 2.6-6.4] years after a 1-year lag). A total of 119 788 patients who were first diagnosed with RA (83 064 with seropositive RA [SPRA], 36 724 with seronegative RA [SNRA]) were identified during the study period and included those who underwent a national health checkup within 2 years before the RA diagnosis date (64 457 patients). After applying exclusion criteria (eg, age <40 years, other rheumatic diseases, previous PD), 54 680 patients (39 010 with SPRA, 15 670 with SNRA) were included. A 1:5 age- and sex-matched control group of patients without RA was also included for a total control population of 273 400.

Exposures

Rheumatoid arthritis as defined using International Classification of Diseases, Tenth Revision codes M05 for SPRA and M06 (except M06.1 and M06.4) for SNRA; prescription of any disease-modifying antirheumatic drug; and enrollment in the Korean Rare and Intractable Diseases program.

Main Outcomes and Measures

The main outcome was newly diagnosed PD. Data were analyzed from May 10 through August 1, 2022, using Cox proportional hazards regression analyses.

Results

From the 328 080 individuals analyzed (mean [SD] age, 58.6 [10.1] years; 74.9% female and 25.1% male), 1093 developed PD (803 controls and 290 with RA). Participants with RA had a 1.74-fold higher risk of PD vs controls (95% CI, 1.52-1.99). An increased risk of PD was found in patients with SPRA (adjusted hazard ratio [aHR], 1.95; 95% CI, 1.68-2.26) but not in patients with SNRA (aHR, 1.20; 95% CI, 0.91-1.57). Compared with the SNRA group, those with SPRA had a higher risk of PD (aHR, 1.61; 95% CI, 1.20-2.16). There was no significant interaction between covariates on risk of PD.

Conclusions and Relevance

In this study, RA was associated with an increased risk of PD, and seropositivity of RA conferred an augmented risk of PD. The findings suggest that physicians should be aware of the elevated risk of PD in patients with RA and promptly refer patients to a neurologist at onset of early motor symptoms of PD without synovitis.

The association between Parkinson's disease and autoimmune diseases: A systematic review and meta-analysis

Parkinson's disease (PD) is a neurodegenerative disorder that frequently occurs in the older population. Previous epidemiological studies have suggested an association between PD and autoimmune diseases (AIDs). However, some studies have shown conflicting results. This study aimed to summarize existing epidemiological studies on the association between PD with AIDs and to conduct a meta-analysis of combinable results. Four electronic databases (PubMed, Embase, Web of Science Core Collection, and MEDLINE) were searched from each database's inception date until December 12, 2022. All studies that explored the relationship between PD and AIDs were included for quantitative analysis and qualitative review. The pooled relative risk with 95% confidence intervals (CIs) was calculated using a random or fixed effects model. A total of 46 observational studies involving 873,643 patients and 13,402,821 controls were included; ultimately, 38 studies were included in the meta-analysis. The risk of PD combined with AIDs was significantly higher (odds ratio [OR]=1.55, 95% CI: 1.33-1.81), and subgroup analysis found no significant differences in risk by study type, gender, age, and race. Regarding the AID types, the results showed an increased risk of PD combined with bullous pemphigoid (OR=2.67, 95% CI: 2.15-3.31), inflammatory bowel disease (OR=1.30, 95% CI: 1.18-1.45), Crohn's disease (OR=1.30, 95% CI: 1.20-1.42), ulcerative colitis (OR=1.31, 95% CI: 1.14-1.50), Sjögren's syndrome (OR=1.61, 95% CI: 1.24-2.09), and Graves' disease (OR=1.45, 95% CI: 1.24-1.70) than controls. However, there appeared to be no significant association between PD and systemic lupus erythematosus (OR=0.82, 95% CI: 0.66-1.03), multiple sclerosis (OR=2.02, 95% CI: 0.87-4.70), rheumatoid arthritis (OR=0.79, 95% CI: 0.61-1.03), or celiac disease (OR=1.16, 95% CI: 0.79-1.69). This study supports the existence of a strong link between AIDs and PD. When PD and AIDs are identified, clinicians need to be aware of the possibility of coexistence. However, there are some limitations of this study, such as the apparent heterogeneity of some of the results and the fact that most of the included study types were retrospective. Therefore, future larger prospective cohort studies are needed to further explore the interaction between PD and AIDs.

Systematic review registration

INPLASY, identifier INPLASY202280088.

Inflammatory rheumatic diseases and the risk of Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Several studies showed inconsistencies in the relationships between inflammatory rheumatic diseases (IRDs) and the risk of Parkinson's disease (PD). Therefore, we carried out a meta-analysis to investigate the associations between different IRDs and PD risk.

METHODS

A comprehensive search was undertaken on PubMed, Embase, Cochrane Library, and Web of Science databases up to June 2022. Studies reporting the relationships between IRDs and PD risk were included. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated by using random-effects models.

RESULTS

Twenty-two publications covering seven IRDs containing data from 833,004 patients were identified for quantitative analysis. The pooled results indicated that ankylosing spondylitis (RR = 1.55, 95% CI: 1.31-1.83, I2 = 32.1%, P < 0.001), Sjögren's syndrome (RR = 1.34, 95% CI: 1.22-1.47, I2 = 58.5%, P < 0.001), and Behcet's disease (RR = 1.93, 95% CI: 1.07-3.49, I2 = 57.6%, P = 0.030) were associated with an increased PD risk. However, no significant associations were observed between gout, rheumatoid arthritis, systemic lupus erythematosus, as well as polymyalgia rheumatica and the subsequent development of PD.

CONCLUSION

Ankylosing spondylitis, Sjögren's syndrome, and Behcet's disease may increase PD risk.

Immunogenetic Determinants of Parkinson’s Disease Etiology

Parkinson’s disease (PD) is increasingly recognised as a systemic disorder in which inflammation might play a causative role rather than being a consequence or an epiphenomenon of the neurodegenerative process. Although growing genetic evidence links the central and peripheral immune system with both monogenic and sporadic PD, our understanding on how the immune system contributes to PD pathogenesis remains a daunting challenge. In this review, we discuss recent literature aimed at exploring the role of known genes and susceptibility loci to PD pathogenesis through immune system related mechanisms. Furthermore, we outline shared genetic etiologies and interrelations between PD and autoimmune diseases and underlining challenges and limitations faced in the translation of relevant allelic and regulatory risk loci to immune-pathological mechanisms. Lastly, with the field of immunogenetics expanding rapidly, we place these insights into a future context highlighting the prospect of immune modulation as a promising disease-modifying strategy.

Bacterial Butyrate in Parkinson's Disease Is Linked to Epigenetic Changes and Depressive Symptoms

BACKGROUND

The gut microbiome and its metabolites can impact brain health and are altered in Parkinson's disease (PD) patients. It has been recently demonstrated that PD patients have reduced fecal levels of the potent epigenetic modulator butyrate and its bacterial producers.

OBJECTIVES

Here, we investigate whether the changes in the gut microbiome and associated metabolites are related to PD symptoms and epigenetic markers in leucocytes and neurons.

METHODS

Stool, whole blood samples, and clinical data were collected from 55 PD patients and 55 controls. We performed DNA methylation analysis on whole blood samples and analyzed the results in relation to fecal short-chain fatty acid concentrations and microbiota composition. In another cohort, prefrontal cortex neurons were isolated from control and PD brains. We identified genome-wide DNA methylation by targeted bisulfite sequencing.

RESULTS

We show that lower fecal butyrate and reduced counts of genera Roseburia, Romboutsia, and Prevotella are related to depressive symptoms in PD patients. Genes containing butyrate-associated methylation sites include PD risk genes and significantly overlap with sites epigenetically altered in PD blood leucocytes, predominantly neutrophils, and in brain neurons, relative to controls. Moreover, butyrate-associated methylated-DNA regions in PD overlap with those altered in gastrointestinal (GI), autoimmune, and psychiatric diseases.

CONCLUSIONS

Decreased levels of bacterially produced butyrate are related to epigenetic changes in leucocytes and neurons from PD patients and to the severity of their depressive symptoms. PD shares common butyrate-dependent epigenetic changes with certain GI and psychiatric disorders, which could be relevant for their epidemiological relation. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Association Between Rheumatoid Arthritis and Risk of Parkinson's Disease: A Meta-Analysis and Systematic Review

Background

Rheumatoid arthritis (RA) and Parkinson's disease (PD) are two common chronic diseases worldwide, and any potential link between the two would significantly impact public health practice. Considering the current inconsistent evidence, we conducted a meta-analysis and systematic review to examine the risk of PD in patients with RA.

Methods

Two investigators (DL and XH) conducted a comprehensive search of PubMed, Embase, and Web of Science using medical subject headings terms combined with free words to identify relevant papers published from inception through December 31, 2021. All studies that explored the relationship between RA and PD were included for quantitative analysis and qualitative review. Random- and fixed-effects models were used to pool the risk ratios (RRs) of PD in patients with RA. The Newcastle-Ottawa scale was used to assess the quality of included studies. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guideline.

Results

Four population-based studies involving 353,246 patients and one Mendelian randomized study were included in our study. The pooled result showed a significantly reduced risk of PD in patients with RA than in the general population (RR = 0.74, 95% CI: 0.56-0.98, P = 0.034). No apparent effects of gender, age, region, follow-up time, or study design on PD risk were observed. Sensitivity analysis showed that pooled results were relatively stable, and no publication bias was detected. The Mendelian randomization study indicated a significant inverse association between RA and PD (genetic correlation: −0.10, P = 0.0033) and that each one standard deviation increase in the risk of RA was significantly associated with a lower risk of PD. Of note, the current study is limited by the relatively small number of included studies and unmeasured confounding factors, especially for RA-related anti-inflammatory agents.

Conclusions

This study supports that people with RA had a lower PD risk than those without RA. Further studies are needed to explore the underlying molecular mechanisms of the interaction between the two diseases.

Immunosuppressants contribute to a reduced risk of Parkinson's disease in rheumatoid arthritis

BACKGROUND

Observational studies have suggested a decreased risk of Parkinson's disease (PD) in patients with rheumatoid arthritis (RA). However, the results are controversial and the biological mechanism underlying this effect remains largely unknown.

METHODS

The effect sizes of five observational studies were summarized to determine the association between RA and PD. A two-step Mendelian randomization (TSMR) analysis was conducted using genome-wide association studies data sets of RA, PD and prescription of non-steroidal anti-inflammatory drugs (NSAIDs), immunosuppressants (IS) and glucocorticoids (GC). A multivariable MR (MVMR) was also performed to verify the impact of prescription history on PD risk.

RESULTS

Integrated data from observational studies showed that RA was associated with a decreased risk of PD in the European population (effect size = -0.38, P = 0.004). We found that genetically predicted RA was correlated with a decreased risk of PD [odds ratio (OR) = 0.91, P = 0.007]. In the TSMR, RA patients tended to have an increased prescription of GC (OR = 1.16, P = 2.96e - 07) and IS (OR = 1.77, P = 5.58e - 64), which reduced the risk of PD (GC: OR = 0.86, P = 0.0270; IS: OR = 0.82, P = 0.0277), respectively. Further MVMR analysis demonstrated that only IS was linked to a decreased risk of PD (OR = 0.86, P = 0.004).

CONCLUSION

This work clarified that patients with RA had a decreased risk of PD, which was partially attributed to the use of IS in RA patients but not GC or NSAIDs.

Autoimmune Disease Associated CLEC16A Variants Convey Risk of Parkinson’s Disease in Han Chinese

CLEC16A is a membrane-associated endosomal protein implicated in regulating autophagy and antigen presentation. Its genetic variants are broadly associated with multiple autoimmune diseases. Parkinson’s disease (PD), which undergoes autophagy disruption and neuroinflammation, has been clinically observed, for an extensive amount of time, to be associated with autoimmune diseases. In this study, we aimed to understand whether the autoimmune disease associated CLEC16A variants pleiotropically modulate PD risk. Five of such CLEC16A variants, including rs6498169, rs12708716, rs12917716, rs7200786, and rs2903692, were selected and analyzed in a Han Chinese cohort comprising 515 sporadic PD patients and 504 controls. Results showed that rs6498169 and rs7200786 were significantly associated with PD susceptibility (p = 0.005 and 0.004, respectively; recessive model, p = 0.002 and 0.001, respectively). Rs6498169 was also associated with the PD subtype of postural instability/gait difficulty (p = 0.002). Haplotype analysis showed that the AAG module in order of rs6498169, rs12708716, and rs2903692 was associated with the highest risk for PD (p = 0.0047, OR = 1.42, 95% CI = 1.11–1.82). Functional annotation analyses suggested that rs6498169 had high probability to affect transcription factor binding and target gene expression. In summary, the current study demonstrates that the autoimmune disease associated CLEC16A variants convey risk of PD in Han Chinese. Our findings suggest a pleiotropic role of CLEC16A and strengthen the link between PD and autoimmune diseases.

Disease-Modifying Antirheumatic Drugs and Risk of Parkinson Disease: Nested Case-Control Study of People With Rheumatoid Arthritis

BACKGROUND

Epidemiological studies have suggested a link between rheumatoid arthritis and Parkinson's disease (PD). Disease-modifying anti-rheumatic drugs (DMARDs) might explain this association.

OBJECTIVE

To evaluate the association between DMARDs and risk of PD in persons with rheumatoid arthritis.

METHODS

Nested nationwide case-control study was conducted within the Finnish Parkinson's disease (FINPARK) cohort that includes 22,189 Finnish persons with clinically verified PD diagnosed in 1996-2015. The cases had recorded diagnosis of PD in the Special Reimbursement Register and had no exclusion diagnoses whose symptoms may be confused with PD within two years of PD diagnosis. This study included cases with PD diagnosed during 1999-2015 and rheumatoid arthritis diagnosed >3 years before PD. Rheumatoid arthritis was identified using Finnish Care Register for Health Care and Special Reimbursement Register. Cases were matched with up to seven control persons by age, sex, duration of rheumatoid arthritis and region. DMARDs were categorised into five classes and data on purchased prescriptions was identified from the Prescription Register since 1995. Associations were studied with conditional logistic regression adjusted for confounders.

RESULTS

Altogether 315 cases with PD and 1,571 matched controls were included. Majority (> 60%) were women and median duration of rheumatoid arthritis on matching date was 11.6 years for controls and 12.6 years for cases. Use of DMARDs was not associated with risk of PD with three-year lag period applied between exposure and outcome, except chloroquine/hydroxychloroquine which associated with decreased risk (adjusted odds ratio 0.74; 95% confidence interval 0.56-0.97). Other DMARDs, including sulfasalazine, methotrexate, gold preparations and immunosuppressants, were not associated with PD.

DISCUSSION

Our results suggest that the lower risk of PD in people with rheumatoid arthritis is not explained by DMARD use as these drugs in general did not modify the risk of PD among persons with rheumatoid arthritis. Association between chloroquine/hydroxychloroquine and lower risk of PD as well as the possible underlying mechanisms should be further investigated.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in individuals with rheumatoid arthritis using DMARDs, only chloroquine/hydroxychloroquine was associated with a potentially decreased risk of developing PD (adjusted OR 0.74, 95% CI 0.56-0.97).

Epidemiological Evidence for an Immune Component of Parkinson's Disease

There is a growing interest in the role the immune system and inflammatory response play on the pathophysiology of Parkinson's disease (PD). Epidemiological evidence lends support for the hypothesis that PD is an immune-mediated condition. An association between inflammatory bowel disease, including Crohn's and Ulcerative colitis, and the risk of PD has been described and replicated in several population-based cohorts. Other autoimmune conditions, such as Sjogren syndrome, ankylosing spondylitis, and rheumatoid arthritis also seem to be associated with an increased risk of PD. Immunosuppressant medications seem to be associated with a decreased risk of PD. Finally, variants in genes involved in immune system regulation are also shared between PD and autoimmune conditions. In this review, we will provide an overview of epidemiological evidence from population-based cohort studies, meta-analyses, and genome-wide association studies that analyze the association between the immune system and PD, discuss current gaps in the literature and future research directions in this field.