The impact of Covid-19 on the PD community
K. Ray Chaudhuri MD, DSc, FRCP
Professor of Movement Disorders and Director of the Parkinson Foundation Centre of Excellence, Kings College, Denmark Hill Campus, London, UK
Covid-19 is a highly infectious coronavirus (SARS-CoV-2) that was first identified in Wuhan, China, at the end of 2019. By March 2020, it was afforded global pandemic status by the World Health Organisation and, by the end of January 2021, Covid-19 had infected around 100 million people and was responsible for over 2 million deaths .
Those infected with the Covid-19 present with a range of symptoms. For many, the clinical presentation is similar to influenza, with fever, cough, hyposmia, loss of taste and shortness of breath [2,3,4]. Diarrhoea as well as neurological symptoms, such as headache and nausea, can also occur. For many, however, severe upper respiratory tract symptoms can rapidly lead to acute respiratory distress, multi-organ failure and death [5,6]. There is also now recognition of the long Covid syndrome, often characterised by severe fatigue and 3 cases of levodopa responsive parkinsonism have also been described post Covid infection [7-10].
Those at highest risk of developing severe symptoms following Covid infection include the frail, the elderly and those with underlying health problems  along with a disproportionately high morbidity and mortality in black and minority ethnic (BAME) populations in the UK . People with Parkinson’s disease (PD), particularly older patients with more advanced disease, who already have respiratory muscle rigidity as well as impairment of cough reflex alongside pre-existing dyspnoea are an especially vulnerable population, with the potential for Covid infection to aggravate dyspnoea, worsen the cough reflex, and thereby lead to aspiration pneumonia and higher mortality. An early analysis  of a first series of ten cases of PD and Covid-19 found that older age and longer disease duration were associated with both susceptibility to infection and a high mortality rate (40%). Of additional concern was that those on advanced therapies, specifically deep brain stimulation and/or levodopa infusion therapy, appeared particularly vulnerable with a mortality rate of 40-50% among the four such cases although there is a bias in the case selection. A recent review has supported these observations with a high risk of hospitalisation and morbidity in people with Parkinson’s and so, by default, those who may be even more compromised by Covid-19 infection .
Whether SARS-CoV-2 infection can precipitate dopaminergic neuronal degeneration, via alpha-synuclein aggregation, inflammation, or some other mechanism, thereby predisposing Covid-infected people to future parkinsonian disorders, has been discussed widely  and merits ongoing investigation .
But while the jury is still out on the potential for a causative link between Covid and PD, it is clear that people with PD do experience a worsening of both motor and non-motor symptoms, which some have termed the ‘hidden sorrow’ [15,16]. Furthermore, government-imposed ‘stay-at-home’ orders, compounded by social distancing and barrier-enforced separation from family, friends and carers, have undoubtedly led to isolation and psychological stress for those with PD . Reduced physical activity has a detrimental impact on both PD symptoms such as pain, fatigue and sleep as well as depression and anxiety in particular [18,19]. The drastic change to lifestyle and routine demanded of us all during the Covid lockdown requires flexible adaptation to changing circumstances; yet this is a cognitive process dependent on normal dopaminergic functioning  and therefore potentially challenging for those with PD.
The impact of Covid – both infection and lockdown – must also be examined and monitored more widely in the PD community. On the frontline of healthcare, PD care providers are both at heightened infection risk themselves and prone to situational stress. Psychological symptoms and poorer quality of life have been reported by 60% of PD caregivers . An inability to work due to Covid infection also presents a risk to the continuity of care within our PD community. The way in which we deliver healthcare during this pandemic must, and is, changing towards more remote technology-assisted provision.
It is important that we monitor the course and impact of this new coronavirus on PD. It will also be important to follow those infected with Covid-19 who have developed specific neurological disturbances, such as sustained hyposmia  given that the olfactory loss reported in many infected patients closely resembles pre-motor symptomatology in PD [2,21]. From a scientific point of view therefore, we need to have robust longitudinal studies in vulnerable subjects, both with and without Parkinson’s to establish the effect of long Covid or susceptibililty to developing Parkinson’s as occurred after the 1918 influenza pandemic.
It may be many years before we understand the true impact of Covid-19 on the PD community, but we have the opportunity now to develop a comprehensive framework of scientific and clinical enquiry that will ensure we collect pertinent data for future interpretation.
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