Parkinson's disease in the Asia-Pacific region
There is a huge and increasing burden of degenerative disorders worldwide.
The Asia-Pacific region is poised to face a large brunt of this, with China alone projected to have the majority of patients with Parkinson's disease within the next couple of decades.
In addition, disease heterogeneity has been increasingly recognized to be a crucial aspect of the disease. Yet, there has been very little study comparing similarities and differences between East and West, despite the fact that in the period 2013-2017 alone, there were around 7,000 PD-related journal publications from China, Japan and South Korea.
In conjunction with the recent World Parkinson Congress (WPC) in Kyoto, Japan, Lancet Neurology published a very timely and state-of-the-art review on "Parkinson's disease in the Western Pacific Region" (Lim et al. 2019). (The WPR is the World Health Organization's terminology for the Asia-Pacific region, minus the Indian subcontinent and a few other countries).
Some of the major highlights were:
Overall, a lower prevalence of PD has been observed in some WPR countries such as Japan and Singapore, despite having a relatively high proportion of aged individuals. There is also a reversal of the usual male predominance of the disease in Japan and South Korea. These findings may point to important differences, e.g., in environmental risk factors, in the region.
There is likely to be a different weightage for PD environmental risk and protective factors in the WPR, relating to pesticide use, smoking, consumption of tea and dairy products, exercise, diabetes, and infections such as hepatitis C. Many of these require further study and if confirmed will have important public health implications.
Some genetic factors underlying PD are distinctly different in WPR populations. Taking the LRRK2 gene as the prototypical example, G2385R and R1628P (so-called "Asian variants") are seen in Asians and not Caucasians with PD, whereas the converse is true for the much more widely-known G2019S mutation. In turn, these genetic differences may have important implications, e.g., in the basic pathogenetic mechanisms (G2019S resulting in increased kinase activity, whereas other mechanisms may be at play with the Asian variants). Understanding these inter-ethnic differences is vitally important as the field enters the era of genetics-based targeted therapies (e.g., LRRK2 kinase inhibitors are currently being tested in clinical trials).
There are differences in medical management in the WPR which may partly account for substantial differences in clinical features such as motor complications (e.g., dyskinesias) and non-motor symptoms. These factors could potentially be exploited or addressed to improve patient symptomatology.
Co-morbid health conditions such as diabetes, cerebral small vessel disease and osteoporosis may be even more highly prevalent in WPR populations, with significant implications for disease causation and/or disease course. These areas are only beginning to be appreciated by the PD clinical and research communities.
There are major gaps in awareness and knowledge of PD (such as confusing PD for ageing, poor recognition of non-motor symptoms, and beliefs that alternative treatments can "cure" PD), which could result in people living with PD not seeking medical care, or leading them to obtain unproven, costly and potentially harmful treatments. Identification of these gaps, as well as patient and caregiver perspectives and preferences will help to inform the design of educational efforts, and a more efficient allocation of healthcare resources to meet patients' and caregivers' needs and goals.
Healthcare resources are insufficient with a shortage of neurologists, PD specialists, and neurosurgeons with expertise in deep brain stimulation (DBS). For example, while the USA has 1 neurologist per 20,000 population, this ratio is 1:300,000 in Malaysia … and around 1:1.5 million in Cambodia and Laos! Currently, there is poor or no access to potentially life-changing treatments such as dopaminergic infusions and DBS in many WPR countries, highlighting an urgent need for stakeholders (patient groups, clinicians, industry and government) to work together to improve the appropriate utilization of these therapies.
There is a paucity of PD-related clinical trials in the WPR, highlighting a major gap in PD research currently, given that there are likely to be inter-ethnic differences in drug metabolism, therapeutic responses and adverse effects. In two Movement Disorder Society-sponsored evidence-based reviews of trials published between 2011 and 2016, fewer than 20% of PD drug trials were conducted in this region. This disparity does not only exist in the PD field, and there are increasing calls for drug developers across medical fields to design studies that represent more of the world's population (https://www.ncbi.nlm.nih.gov/pubmed/?term=knepper+nature+2018).
Complementary and alternative treatments are even more widely used in the WPR (by up to three-quarters of PD patents) than in the West, reflecting many factors including cultural history, easy access, and a desire for a more holistic approach to health care. The most popular approaches include tai chi, acupuncture, and herbal preparations. There is therefore a need for these treatments to be tested in a rigorous manner as for conventional therapies, in order to provide an evidence-based, scientific rationale for their use.
A number of specific suggestions on how the field can move forwards in terms of further research, short and medium-term priorities for care, and opportunities for improvements in training and advocacy in the region, were discussed in this multi-authored paper. Readers are encouraged to peruse this document (https://www.ncbi.nlm.nih.gov/pubmed/31175000); it is our sincere hope that there will be much more analysis, discussion and debate regarding the issues raised here.
Shen-Yang Lim, MD, FRACP presented a plenary lecture on Managing the "Peripheral" Problems in PD at the 5th World Parkinson Congress in Kyoto, Japan and was on faculty at the 4th World Parkinson Congress in Portland, OR, USA. He is currently a professor at the University of Malaya Mah Pooi Soo and Tan Chin Nam Centre for Parkinson's & Related Disorders in Kuala Lumpur, Malaysia.
Ideas and opinions expressed in this post reflect that of the author solely. They do not necessarily reflect the opinions or positions of the World Parkinson Coalition®