Based on the geographical distribution of multiple sclerosis (MS) and the changes in risk that occur with migration, there has always been a suggestion that some kind of infectious agent or agents are involved in disease etiology. However, no agent has been identified conclusively.
A study from Denmark previously had shown that the risk of MS is lower in patients with HIV compared with those not infected with HIV. However, the result was not statistically significant.
The authors of a current study used a large UK dataset to see if HIV infection is associated with lower MS risk.
The study used data from the English Hospital Episode Statistics (HES). HES collects data on admissions to hospitals in England for the entire population of England (about 50 million people). Admissions are given a diagnostic code, and patients’ hospital admissions can be linked together over time (termed record-linkage).
In this study, the researchers had data on hospital admissions between 1999 and 2011. They identified patients initially admitted for HIV and then assessed their subsequent risk of being admitted for MS compared with people initially admitted for minor acute conditions.
Overall, the risk of being admitted for MS in people with HIV, relative to those without HIV, was 0.38 (95% confidence interval, 0.15 to 0.79).
With the use of routinely collected health care data, this study has many limitations. It has few data on potential confounders (eg, ethnicity) and, importantly, hospital admissions are used as a proxy for diagnosis.
Given the data from Denmark, however, being infected with HIV does seem to be “protective” against MS development. The researchers speculate on 2 potential mechanisms for the association:
• First, immunodeficiency induced by HIV itself may prevent the development of MS.
• Second, antiretroviral medications used to suppress HIV replication may suppress other viral pathogens implicated in MS, for instance, human endogenous retroviruses and herpes viruses.
Further work is needed to confirm this association and, if it is confirmed, the mechanism behind it.
1. Gold J, Goldacre R, Maruszak H, et al. HIV and lower risk of multiple sclerosis: beginning to unravel a mystery using a record-linked database study. J Neurol Neurosurg Psychiatry. 2014 Aug 4. pii: jnnp-2014-307932. doi: 10.1136/jnnp-2014-307932. [Epub ahead of print]