Risk of Parkinson's disease lower in people treated for hepatitis C

Keith Alcorn
Published:
18 June 2019

People with hepatitis C who received interferon-based treatment were less likely to develop Parkinson’s disease, a large study from Taiwan has concluded. The results, published in JAMA Neurology, add to the evidence that hepatitis C is a risk factor for developing Parkinson’s disease and that antiviral treatment may reduce this risk, say the study authors.

Parkinson’s disease is a degenerative neurological condition that leads to tremors, slowed movement and eventually to difficulties in walking, standing and swallowing. The risk of developing Parkinson’s disease increases with age and several epidemiological studies have shown that hepatitis C infection increases the risk of developing Parkinson’s disease.

However, epidemiological studies have not looked at the impact of antiviral treatment for hepatitis C on the incidence of hepatitis C. This is a concern owing to reports of the emergence of Parkinson’s-like symptoms in some people after they began interferon treatment for hepatitis C.

To clarify the relationship between hepatitis C, interferon-based treatment and Parkinson’s disease, investigators in Taiwan looked in the National Health Insurance Database for all people with hepatitis C. They sought to identify all cases of Parkinson’s disease diagnosed more than six months after completing treatment with interferon alpha and ribavirin, between January 2003 and December 2013.

To be eligible for inclusion in the analysis, patients had to be over 20 years of age, without liver cirrhosis or any serious liver disease, dementia or Parkinson’s disease. People treated for less than 16 weeks or with less than six months of follow-up were excluded. The investigators identified 188,152 eligible patients, of whom 39,989 had undergone treatment. The treated people were matched 1:1 with people from the untreated group by age, sex, co-morbidities and medication.

The mean age of the study population was 52 years, 55% were male and approximately 13% had diabetes.

The incidence and risk of developing Parkinson’s disease was calculated at one year, three years and five years of follow-up. The incidence of Parkinson’s disease was 1 per 1000 person-years in the treated group and 1.39 per 1000 person-years in the untreated group.

Although there was no difference in the risk of developing Parkinson’s disease after one year or three years of follow-up, a significant difference in risk was evident after five years of follow-up. Treated people were around 25% less likely to have developed Parkinson’s disease by this point (HR, 0.75; 95%CI, 0.59-0.96).

When analysed by sub-group, people using calcium channel blockers who received interferon treatment had a more substantial reduction in risk than those who did not use calcium channel blockers (HRs of non-dCCBs and CCBs, 0.81 vs 0.44; P for interaction = .02). Approximately 13% of treated and untreated people were taking a calcium channel blocker. Calcium channel blockers have been associated with a lower risk of developing Parkinson’s disease in the general population too.

The investigators say that the results show that interferon treatment does not raise the risk of Parkinson’s disease in people with hepatitis C. A 6-month course of interferon treatment is unlikely to exert a protective effect five years later, they argue. Instead, they argue that treatment may limit the direct neurotoxic effect of hepatitis C, by clearing the virus from the brain.

But the investigators warn that the long period over which Parkinson’s disease develops makes it difficult to judge whether treatment with interferon prevents or arrests the development of the condition. The study could not distinguish between people cured of hepatitis C and those who did not respond to treatment. Nor does it provide any information about the impact of direct-acting antivirals on the risk of developing Parkinson’s disease.

Reference

Lin W-Y et al. Association of antiviral therapy with risk of Parkinson Disease in patients with chronic hepatitis C infection. JAMA Neurology, advance online publication, 5 June 2019. doi:10.1001/jamaneurol.2019.1368

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