Parkinson’s disease is more common among people with hepatitis B or C than in the general population in England, a cohort study that looked back from 1999 to 2011 has found. The researchers say it is unlikely that the increased risk is due either to drugs used in treatment or to cirrhosis. The findings are published in advance of print online in the journal Neurology.
Parkinson’s disease is a neurodegenerative disease that leads to tremors, problems with balance, slowing of movement, muscle stiffness, involuntary movements of the limbs, and eventually to more severe disability. Parkinson’s disease cannot be cured but its symptoms can be moderated with treatment.
In the United Kingdom, the lifetime risk of developing Parkinson’s disease is 4%, or 1 in 25. The disease is more common in men and in people aged 60 and over. Smokers appear less likely to develop Parkinson’s disease.
Researchers from the University of Oxford and UCL Institute of Neurology assembled a national cohort of people with viral hepatitis, autoimmune hepatitis or HIV by using English National Hospital Episode Statistics to identify all people with these conditions seen as a day patient or in-patient at an NHS hospital in England between 1999 and 2011. These patients were then followed to see how many were diagnosed with Parkinson’s disease. Their risk of developing Parkinson’s disease was compared with a reference cohort of people without any of these conditions who attended a hospital during the same period for minor surgery. The study excluded people already diagnosed with Parkinson’s disease at the time they attended a hospital.
|
Cohort
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Cohort number
|
Relative risk
|
|
Reference cohort
|
6,132,124
|
Reference group
|
|
Hepatitis B
|
21,633
|
1.76 (1.28-2.37, p<0.001)
|
|
Hepatitis C
|
48,428
|
1.51 (1.18-1.90, p<0.001)
|
|
Autoimmune hepatitis
|
6,225
|
1.59 (non-significant)
|
|
Chronic active hepatitis
|
4,234
|
1.15 (non-significant)
|
|
HIV
|
19,870
|
1.16 (non-significant)
|
The study found that the risk of developing Parkinson’s disease during follow up was around 75% higher for people with hepatitis B and approximately 50% higher for people with hepatitis C compared to the general population.
The study could not control for smoking or alcohol use and could not take into account treatment for viral hepatitis, cure of hepatitis C infection or the presence of cirrhosis.
The authors say that they don’t consider interferon treatment of viral hepatitis to be a plausible risk factor because a previous study which also found an association between Parkinson's disease and viral hepatitis was carried out before interferon treatment was funded in Taiwan.
Although cases of parkinsonism (Parkinson’s-like symptoms) have been related to cirrhosis by investigators, the authors of this study say that the rarity of this diagnosis makes it an unlikely explanation for the increased risk.
In an accompanying editorial, Julián Benito-León of Complutense University, Madrid, says that for HCV to be proven as a cause of Parkinson’s disease, studies are needed to show the impact of direct-acting antiviral treatment on the incidence of Parkinson’s disease and the progression of symptoms. Research into how HCV affects the brain – and leads to Parkinson’s disease – might also shed more light on how the disease develops and how its progression could be prevented.