Determining exactly how many individuals there are in the world that are affected by Parkinson’s is a difficult task. Previously, a lot of ‘gues-stimation’ has been used in these quantitative efforts. But a clearer idea of the geographical, national and regional spread of Parkinson’s burden, could provide us with very useful information to help better understand the condition.
The Global Burden Disease Collaborators conducted a world-wide assessment of Parkinson’s burden in 2016, and this week the results of their study were published. The findings make for interesting reading.
In today’s post, we will review the results and discuss what they mean for the Parkinson’s community.
This is one of those classic ‘boy meets girl’ stories… but with a ‘saves the world’-kind of twist to it.
Having just graduated from Duke University (with a degree in computer science and economics) in the summer of 1986, Melinda Ann French began working as an intern for IBM. Having learnt to program (in Basic) on Apple II computers during her teens, she was interested in a future career in the developing world of computer technology.
She eventually scored a job with a new company called Microsoft, and for the next 6 years she climbed the corporate ladder, from a software marketing position to general manager of information products (such as Microsoft Bob, Expedia, and Encarta).
Melinda met William (Bill) Henry Gates III four months after starting her job at Microsoft – they happened to sit next to each other at a trade-fair dinner in New York. But several months would pass by before Bill actually asked her out on a date.
They were married in Hawaii on New Years day 1994.
In 2000, the couple launched the Bill and Melinda Gates Foundation – which has gone on to become one of the largest private foundations in the world with US$50+ billion in assets.
Excuse me, this is all very interesting, but what does it have to do with Parkinson’s?
The primary goals of the Bill and Melinda Gates foundation are to enhance healthcare and reduce extreme poverty globally, and to expand educational opportunities and access to information technology in the US. As part of this mission, the foundation funds a lot of research looking into issues related to various medical conditions.
This week some research funded by the Bill and Melinda Gates foundation was published and it was focused on determining the global, regional, and national burden of Parkinson’s.
Here is the research report:
Title: Global, regional, and national burden of Parkinson’s disease, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016
Authors: The Global Burden Disease 2016 Parkinson’s Disease Collaborators
Journal: Lancet Neurol. 2018 Oct 1. pii: S1474-4422(18)30295-3
PMID: 30287051 (This report is OPEN ACCESS if you would like to read it & there is an associated editorial)
In this study, the researchers aimed to determine the global burden of Parkinson’s (the total number of people with the condition) between the year 1990 and 2016. The goal was to “identify trends and to enable appropriate public health, medical, and scientific responses”.
This project was a follow-on study to a report of global, regional, and national burden of neurological disorders in general, which was published by the same researchers last year (Click here to read that report). Critically, that previous report had found that of all the major neurological conditions (think, epilepsy, Alzheimer’s, etc), Parkinson’s “was the only neurological disorder with increasing age-standardised rates of deaths, prevalence, and DALYs” (DALYS stands for ‘disability-adjusted life-years’).
The result suggested that the incidence of Parkinson’s was increasing at a higher rate th an could be explained by the overall increase of our aging populations in the Western world.
The researchers did not see the same trend for Alzheimer’s which is also a neurodegenerative condition associated with ageing. Naturally, this finding caused some eyebrow raising, and required replication and further investigation.
The report published this week represents replication and further investigation.
So how did they conduct their analysis?
The Global Burden Disease Collaborators conducted a systematic analysis of epidemiological studies.
They began by using the Pubmed search engine, and searching for research reports with the keywords “Parkinson disease” and “epidemiology” that were published between Jan, 1, 2011, and Dec, 31, 2015. Papers were selected if representative of the general population and identification of cases was based on the mentioning of diagnostic criteria including International Classification of Diseases ninth revision (ICD-9) codes or the UK Parkinson’s Disease Society Brain Bank criteria.
This search resulted in 127 sources of data on Parkinson’s, including 91 sources on prevalence across 16 of the 21 Global Burden disease world regions, as well as 34 sources on Parkinson’s incidence covering nine world regions, and 11 sources on mortality risk covering two world regions.
In the case of prevalence, the majority of the studies (44·0%) had been conducted in western Europe. In addition to this:
- Nine (9·9%) had been conducted in east Asia
- Seven (7·7%) in high-income Asia Pacific
- Seven (7·7%) in high-income North America
- Seven (7·7%) in North Africa and Middle East.
- 21 (23·0%) studies were from other regions
These other regions did not include central Asia, central Latin America, tropical Latin America, central sub-Saharan Africa, and southern sub-Saharan Africa – where no data was available.
Ok, and what did all this analysis find? What were the results?
The headline result of the study is that in 2016 there were 6·1 million individuals worldwide living with Parkinson’s.
Of these, 3·2 million (52·5%) were men and 2·9 million (47·5%) were women – this last result surprised me a little as previous sex ratios have indicated a higher male burden.
Of the 6.1 million, 34·4% (or 2·1 million) lived in high socio-demographic index (SDI) countries, 50·8% (3·1 million) lived in middle SDI countries, and just 14·8% (0·9 million) lived in low SDI countries.
But one of the really interesting result in the data was that the number of individuals living with Parkinson’s in 2016 was 2·4 times higher than that in 1990 (2·5 million). This increase could not be explained by the increasing number of older people, which grew at a slower rate. And curiously this increase in the number of people living with Parkinson’s was less pronounced in high SDI countries (9·2% compared to 59·8% in middle SDI countries).
And as the map below suggests, the prevalence rates of Parkinson’s by country varied greatly, with the highest rates generally in North America and lowest rates in sub-Saharan Africa.
And here is the number that nobody wants to read, but I’m going to share it – in 2016, Parkinson’s was associated with 211 296 deaths worldwide. And this number was 2·6 times higher than the same statistic in 1990.
Parkinson’s is a condition generally associated with ageing, and the prevalence of the condition in 2016 was found to increase with age, peaking between 85 years and 89 years (where it was present in 1·7% of men and 1·2% of women in the population).
The investigators also found that smoking was associated with “a small, protective effect on Parkinson’s”, which agrees with a lot of previous research (Click here to read a previous SoPD post on this topic).
So how do the researchers explain the increase in incidence?
They proposed that it could be explained by several possible reasons. Increased life expectancy, for example, could be partly contributing to a situation of longer disease duration in individuals with Parkinson’s. People living longer with the condition would result in more people living with Parkinson’s. This idea is supported by a recent meta-analysis of 10 studies suggested that longer disease duration, with an increase of 2·5 years per decade. But that meta analysis study also indicated that there is no evidence that the introduction of L-dopa had led to increases in survival of individuals with Parkinson’s.
The increase in Parkinson’s burden might also be linked to either environmental factors (such as pollution from growing industrialisation) or reductions in the levels of smoking around the world (if smoking is protective against PD, then cessation on a population level may result in more cases of PD).
Ultimately, however, the researchers admit that they do not know and that further research is required to investigate this.
So what are the implications of this data for the PD community?
One obvious take away from the study is the need for more urgency on Parkinson’s research. If it is increasing in incidence (while other neurological conditions are not), there is a common communal interest in determining why. And uncovering the reason for the increase may help us to better understand the condition itself.
Thus, more research is required.
In addition, the researchers behind the study have suggested additional responses that could be implemented to help prevent the any further increase in the incidence of the condition. These included
- Increasing physical activity earlier in adulthood (Click here to read an interesting commentary on this)
- Reducing exposure to pesticides (Click here to read more about this)
- Improving worldwide access to care/treatments (an obvious solution)
- Development of new therapies (dito!)
So what does it all mean?
When young Bill Gates first started playing with some of the early computers, do you think he ever dreamed that he would end up building one of the largest tech companies in the world and then run one of the largest private foundations in the world, (dealing with health issues on a global scales)?
Young Bill Gates. Source: Businessinsider
A tiny part of that global health effort has recently been focused on the global, regional and national burden of Parkinson’s. The research gives us a reasonable estimation of the total number of individuals in the world living with the condition (6 million) and also points towards a disturbing trend of increasing incidence.
I guess the hope is now that the Bill and Melinda Gates Foundation will follow up this research by funding further investigations of why the incidence of Parkinson’s is increasing.
One can hope at least.
The banner for today’s post was sourced from winzeler