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. 

Hepatitis C virus infection and risk of Parkinson's disease: a systematic review and meta-analysis

Results from our study using HES data earlier this year have been meta-analysed with data from other published studies. The results are not surprising (Hep C is associated with increased risk of PD) but the mechanism is intriguing and requires further study... whether it is a percularlity of the virus, the treatment or a shared susceptibility remains to be seen...

Eur J Gastroenterol Hepatol. 2017 Oct 18. doi: 10.1097/MEG.0000000000000991. [Epub ahead of print]
Wijarnpreecha K, Chesdachai S, Jaruvongvanich V, Ungprasert P.

https://insights.ovid.com/pubmed?pmid=29049127

BACKGROUND/OBJECTIVE: Hepatitis C virus (HCV) infection is one of the most common infections worldwide. Recent epidemiologic studies have suggested that patients with HCV infection might be at an increased risk of Parkinson's disease. However, the data on this relationship remain inconclusive. This meta-analysis was conducted with the aim to summarize all available evidence.

PATIENTS AND METHODS: A literature search was performed using MEDLINE and EMBASE database from inception to May 2017. Studies that reported relative risks, odd ratios (ORs), or hazard ratios comparing the risk of Parkinson's disease among HCV-infected patients versus participants without HCV infection were included. Pooled OR and 95% confidence interval were calculated using a random-effect, generic inverse variance method.

RESULTS: Of 468 studies, five studies with 323 974 participants met our eligibility criteria and were included in the analysis. We found a higher risk of Parkinson's disease among patients with chronic HCV infection compared with participants without HCV infection with the pooled OR of 1.35 (95% confidence interval: 1.19-1.52). The statistical heterogeneity of this study was insignificant (I=3%). The main limitation of this meta-analysis was the limited accuracy of diagnosis in the primary studies as they were coding-based studies.

CONCLUSION: This study demonstrated a higher risk of Parkinson's disease among HCV-infected patients. Further studies are required to clarify how this risk should be addressed in the clinical picture.