PLAIN ENGLISH: Organ transplants and risk of Parkinson's

This is another interesting study borne out of large USA health insurance databases (Medicare database). The team from Washington noticed, whilst using the same data to see if they could identify people at high risk of Parkinson’s, that people with Parkinson’s were less likely to have received an organ transplant than someone without Parkinson’s. This implies that people who have had organ transplants have a reduced risk of Parkinson’s. They decided to investigate this further because it could important implications in developing a medication to prevent Parkinson’s.

They identified 94,155 people with Parkinson’s and then they randomly selected 118,295 people without Parkinson’s in a similar age group. Overall 278 people with Parkinson’s had also had a tissue transplant and 302 of the people without Parkinson’s had a tissue transplant. They found that the odds of having Parkinson’s after a tissue transplant were reduced.

It’s unclear what is causing this effect but one of the possibilities is the medication that transplant patients are on. People who have received transplants are usually started on medication that lowers the body’s immune system to prevent the body rejecting the transplant. It is possible that these medications could be protecting the brain in some way from Parkinson’s. Unfortunately we cannot be sure at the moment and more research is needed to understand the science underlying this!

Parkinsonism Relat Disord. 2019 Feb 14. pii: S1353-8020(19)30059-8. doi: 10.1016/j.parkreldis.2019.02.013. [Epub ahead of print]

Transplant and risk of Parkinson disease.

Fan J¹, Searles Nielsen S², Faust IM³, Racette BA⁴.

Author information

Abstract

INTRODUCTION:

The pathophysiology of Parkinson's disease (PD) remains unclear, but growing evidence supports a role of neuroinflammation. The purpose of this study was to investigate the association between tissue transplantation and PD risk, given the importance of immunosuppressants in post-transplant management.

METHODS:

We performed a case-control study among Medicare beneficiaries age 66-90 using claims from 2004 to 2009. We used International Classification of Diseases, Ninth Edition (ICD-9) and Current Procedural Terminology (CPT) codes to identify PD (89,790 incident cases, 118,095 population-based controls) and history of tissue transplant (kidney, heart, liver, lung, and bone marrow). We investigated risk of PD in relation to tissue transplant in logistic regression models, adjusting for age, sex, race, smoking, and overall use of medical care.

RESULTS:

Beneficiaries who had received a tissue transplant at least five years prior to PD diagnosis or reference had a lower risk of PD (odds ratio [OR] 0.63, 95% confidence interval [CI] 0.53, 0.75) than those without tissue transplant. This inverse association was observed for kidney (OR 0.63, 95% CI 0.47, 0.84), heart (OR 0.58, 95% CI 0.40, 0.83), lung (OR 0.41, 95% CI 0.21, 0.77), and bone marrow (OR 0.57, 95% 0.38, 0.85) transplants. Associations were attenuated, but remained, following adjustment for indications for the respective type of transplant. Liver transplant was not associated with PD risk.

CONCLUSIONS:

Patients undergoing tissue transplant may have a lower risk of developing PD than the general population. Further studies are needed to determine if this association is causal and if immunosuppressants mediate this association.

Why more Parkinson's might not be such a bad thing

This week, the Lancet Neurology have published the "Global, regional, and national burden of Parkinson’s disease, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016", a very large and very complex analysis of the amount of Parkinson's all over the world.

As can be seen from the map below, there are huge differences in the rate of Parkinson's. Some of the reasons for this are clear, and some are less well understood.

Worldwide rates of people with Parkinson's (age-standardised prevalence per 100,000 population in 2016)

What is more interesting is the rates of change. Parkinson’s was the fastest growing condition in terms of prevalence, disability and death of all neurological conditions. Since 1990, the prevalence (number of people with a condition), mortality, and disability-adjusted life-years (One DALY can be thought of as one lost year of "healthy" life. Read more about DALYs here), have more than doubled. In part this is because of the population of the world getting older. This figure shows the rates of Parkinson’s for men and women at different ages.

The percentage of men (red) and women (blue) with Parkinson's by age. The line is  the current estimate, with the shaded area being the region of uncertainty in which the 'true' figure lies.

Although there are many reasons why this increase is being seen, one reason is that the prevalence is related to two things: how many people receive a new diagnosis, but also how long people with a condition live with it. If the rate of new diagnoses has not significantly changed (the evidence remains unclear), in a generation we have enabled people with Parkinson’s to live longer. The authors remind us that this is only partly due to drugs like levodopa, and also due to the general increase in sanitation, food security, general health improvement, vaccination etc. as well as attention to things like physiotherapy, speech and language therapy etc.

So as we go forward, lets hope that the number of people with Parkinson’s continues to increase, but the DALYs decrease. And lets continue to work hard so we can at last make a real change to the incidence of Parkinson’s.

RNR

GBD 2016 Parkinson's Disease Collaborators. Global, regional, and national burden of Parkinson's disease, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. The Lancet Neurology. 2018 Oct 1;17(11):939–53. 

Prevalence of Parkinson's disease across North America

This study looks at the current and projected prevalence of Parkinson's in the USA. Although the sources of data vary substantially, the authors do a good job of combining estimates and provide clear discussion for why estimates from some sources may lack precision. This kind of work is essential for planning health care resources, now and in the future. It also puts into sharp focus the increasing burden of disease and what neuroprotective therapies would mean in the fight against the rising tide....

Alastair Noyce

NPJ Parkinsons Dis. 2018 Jul 10;4:21. doi: 10.1038/s41531-018-0058-0. eCollection 2018.
Marras C, Beck JC, Bower JH, Roberts E, Ritz B, Ross GW, Abbott RD, Savica R, Van Den Eeden SK, Willis AW, Tanner CM; Parkinson’s Foundation P4 Group.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039505/

Estimates of the prevalence of Parkinson's disease in North America have varied widely and many estimates are based on small numbers of cases and from small regional subpopulations. We sought to estimate the prevalence of Parkinson's disease in North America by combining data from a multi-study sampling strategy in diverse geographic regions and/or data sources. Five separate cohort studies in California (2), Minnesota (1), Hawaii USA (1), and Ontario, Canada (1) estimated the prevalence of PD from health-care records (3), active ascertainment through facilities, large group, and neurology practices (1), and longitudinal follow-up of a population cohort (1). US Medicare program data provided complementary estimates for the corresponding regions. Using our age- and sex-specific meta-estimates from California, Minnesota, and Ontario and the US population structure from 2010, we estimate the overall prevalence of PD among those aged ≥45 years to be 572 per 100,000 (95% confidence interval 537-614) that there were 680,000 individuals in the US aged ≥45 years with PD in 2010 and that that number will rise to approximately 930,000 in 2020 and 1,238,000 in 2030 based on the US Census Bureau population projections. Regional variations in prevalence were also observed in both the project results and the Medicare-based calculations with which they were compared. The estimates generated by the Hawaiian study were lower across age categories. These estimates can guide health-care planning but should be considered minimum estimates. Some heterogeneity exists that remains to be understood.