A new study published in Neurology on March 29th has indicated a potential link between Hepatitis B and C, and Parkinson’s disease (PD).1 Data for the paper was collected from the English National Hospital Episode Statistics, and was analyzed as a retrospective cohort study. Day-case and inpatient hospital care information was collected from individuals seeking medical care for a large number of medical procedures—from bunions, to varicose veins, to knee replacement surgery and hemorrhoids—between the years of 1999 and 2011.
Those with hep C or B more likely to develop PD
Specifically, 21,633 individuals with Hepatitis B, 48,428 individuals with Hepatitis C, 6,225 individuals with autoimmune hepatitis, 4,234 with chronic active hepatitis, and 19,870 with HIV were analyzed, along with a control reference group of over 6 million individuals without any of the conditions, who came to the hospital for the same medical procedures. A series of rate ratios (RR’s) were calculated for each group, to determine the expected and observed incidences of PD. To prevent from confusing the direction of the link, and to make sure the researchers were studying if hepatitis or HIV increases the risk of PD and not the other way around, the researchers only utilized individuals in the PD group who experienced PD symptoms at least a year or longer after exposure to hepatitis or HIV.
“We observed significant associations for hepatitis B and C only, but not the other studied exposure diseases. These findings are therefore likely explained by a specific aspect of viral hepatitis — rather than a general hepatic inflammatory process or general use of antivirals — but whether this reflects shared disease mechanisms, shared genetic or environmental susceptibility, sequelae of viral hepatitis per se, or a consequence of treatment remains to be determined.”
-Julia Pakpoor, BA, BM, Bch, Unit of Health Care Epidemiology, Nuffield Department of Population Health, University of Oxford, United Kingdom, and Lead Author
Overall, the study found that the RR value for individuals with Hepatitis B was 1.76, and the RR value for individuals with Hepatitis C was 1.51, with respect to developing PD. This means that individuals with Hepatitis B had a 76% higher risk of developing PD than those without the condition, and those with Hepatitis C had a 51% higher risk. The researchers found that the other forms of hepatitis analyzed, as well as HIV, did not show a significant increase in risk for developing PD. The authors did note, however, that autoimmune hepatitis was very close to showing significant risk.
More research is needed
“Clinicians caring for patients with a history of hepatitis B or C should be aware of this seeming increased risk of PD among their patients, so that if neurological symptoms present, these are detected early. We hope that in the long term, our work will contribute in providing neurologists with a greater understanding of causal pathways in PD.” -Julia Pakpoor
This information not only points towards the need for future research on the shared pathways of PD and Hepatitis B and C, but also points towards the need for individuals and providers to pay close attention to potential neurological symptoms. The researchers were unable to control or monitor all confounding variables, such as medications taken, genetic and environmental health factors, and previous medical history, however, despite this, the report is still regarded as solid, and indicative of a larger issue at hand.
Further studies will need to be directed towards not only establishing the link between these conditions, but discovering what exactly that link is. Current theories center around Hepatitis C virus receptors being expressed on blood-brain barrier cells, opening the door for potential CNS involvement, and the possibility that those with hepatitis could present with a higher level of neuronal toxicity than their healthy counterparts, based on a recent animal study.2, 3
Pakpoor J, et al. “Viral hepatitis and Parkinson disease.” Neurology. 29 Mar 2017. Abstract available from: http://www.neurology.org/content/early/2017/03/29/WNL.0000000000003848
Anderson, Pauline. “Hepatitis B and C linked to Parkinson’s.” Medscape. 29 Mar 2017. Available from: http://www.medscape.com/viewarticle/877926?nlid=113790_4421&src=wnl_dne_170330_mscpedit&uac=259022DR&impID=1319091&faf=1#vp_1
Bakalar, Nicholas. “Hepatitis tied to Parkinson’s risk.” The New York Times. 30 Mar 2017. Available from: https://www.nytimes.com/2017/03/30/well/live/hepatitis-tied-to-parkinsons-risk.html?_r=0