According to a study published in the Journal of Neurology Neurosurgery & Psychiatry, HIV infection is correlated to a significantly lower risk of developing multiple sclerosis (MS).
The researchers analyzed a previous report by a team of Danish researchers whereby an HIV positive man with MS had his symptoms resolved completely after starting combination antiretroviral therapy for his infection. The authors hypothesized that the antiretroviral drugs were coincidentally treating or preventing progression of MS, leading them to conduct an epidemiological study on the incidence of MS in a newly diagnosed HIV population. Although the incidence ratio for an HIV patient acquiring MS was low, the numbers were too small to reach any statistical significance.
Prompted by this statistical gap, a team of researchers from the UK set out to conduct a larger comparative study to further investigate the possible association between HIV and MS.
They accessed one of the world’s largest linked medical data sets, with a cohort of 21,207 HIV-positive patients and 5,298,496 controls stratified by age, sex, year of first hospital admission, and socioeconomic status, all of which were registered between 1999 and 2011.
The development of MS was analyzed in all participants for seven years, revealing that HIV-infected individuals were 62% less likely to develop MS, based on seven actual diagnoses of MS during that time frame. Moreover, the longer the time between a diagnosis of HIV and one of MS, the higher degree of protection conferred by HIV, since more than one year or more than five years between diagnosis resulted in 75% and 85% less probability, respectively.
Although these findings are in agreement with those from the original study, they are statistically significant — albeit speculative rather than definitive — since no information was available on whether the HIV positive participants were treated with antiretroviral drugs or for how long. The hypothesis now states that HIV infection itself halts the development of MS, or that the antiretroviral drugs used to stop HIV proliferation can exert the same effect on eventual viral agents involved in the development of MS.
Nevertheless, further research is needed to prove these results are not just a hypothesis, demonstrating beyond doubt that there is indeed a causal protective effect of HIV or its treatment. If so, this would be the largest protective effect observed to date in relation to the development of MS.