People living with HIV significantly less likely to develop MS: Study

Virus, antiretroviral treatment may confer protective effect

Patricia Inacio, PhD avatar

by Patricia Inacio, PhD |

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Living with the human immunodeficiency virus (HIV) is linked to a significantly lower rate of developing multiple sclerosis (MS) — including among people exposed to antiretroviral treatment, or medicines that can stop the HIV virus from replicating — a new study found.

The rate of MS was particularly reduced in HIV-infected women. Meanwhile, no differences in MS development were observed in men infected with the virus.

“Using an international multicenter approach, we report a lower occurrence of MS in individuals living with HIV than expected,” the researchers wrote.

“These results suggest that infection with HIV or treatment with [antiretroviral therapy] may confer a protective effect against the development of MS,” the team wrote.

The findings, presented at the Americas Commitee for Treatment and Research in Multiple Sclerosis (ACTRIMS) meeting in early 2023, now have been published in a study, titled “Risk of Multiple Sclerosis in People Living with HIV: An International Cohort Study,” in the journal Annals of Neurology.

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Study examined effect of antiretroviral treatment on MS development

Prior studies have reported that people living with HIV have lower rates of MS than would be expected in the general population. Because that virus infects and destroys immune cells called CD4-positive T-cells — which have been implicated in the early development of MS — their lower numbers are likely the reason.

However, such previous studies were either small or did not account for the potential effects of antiretroviral therapies, which are used to keep HIV in check. Thus, according to researchers, “the question of whether HIV or its treatment with [antiretroviral therapy] has a mitigating effect on MS risk remains unresolved.”

To answer this, a team of researchers from Sweden, Canada, and the U.K. analyzed the incidence of MS among HIV-positive people from two population-based studies, one in Sweden and one from British Columbia (BC), in Canada. The study in Sweden was launched in 2001, while the one in BC was started in 1992.

Next, using MS registries in both countries, the team compared the incidence of MS among those living with HIV with that of  the corresponding general population. The scientists also assessed the potential influence of the antiretroviral therapy on the incidence rates.

The analysis included a total of 29,163 people with HIV: 10,390 in Sweden and 18,773 in Canada. In both groups, more than half of the patients were men (65.9% in Sweden and 79.9% in BC). The median age at HIV infection was in the mid to late 30s.

The participants were followed for an average of 10.1 years in the Swedish group and 8.9 in the Canadian group. Patients received antiretroviral therapy during 86.1% of that follow-up time.

Using statistical models that accounted for age, calendar year, region of birth, and socioeconomic status, the team calculated the standardized incidence ratio (SIR) of MS – meaning the ratio of newly diagnosed MS cases among HIV-patients versus those diagnosed in the general population.

The analysis revealed that 26.2 new cases of MS were expected among the HIV-positive group, assuming that people living with HIV would have a similar incidence compared with the general population. However, only 14 actual cases of newly diagnosed MS were recorded, meaning that HIV-infected people had a 47% lower incidence than expected.

This large population-based international study revealed a significantly lower risk of MS among individuals living with HIV, and among HIV-positive [antiretroviral therapy]-exposed individuals, than expected based on the risk in the general population.

When HIV-infected people were divided by sex, however, only women infected with the virus had a significantly lower incidence of MS — 72% lower than would be expected. The incidence in HIV-infected men also tended to be lower than in men of the general population, but the difference failed to reach statistical significance.

Similar reductions in MS incidence were observed during exposure to antiretroviral therapies. In the whole HIV-infected population, the rate of MS during exposure to treatment was 45% lower than in the general population. And again, this difference was only significant in women, with HIV-infected patients being 75% less likely to develop MS during treatment.

Overall, “this large population-based international study revealed a significantly lower risk of MS among individuals living with HIV, and among HIV-positive [antiretroviral therapy]-exposed individuals, than expected based on the risk in the general population,” the study concluded.

The researchers also suggested that these results “might also motivate a more concerted effort to ascertain whether [antiretroviral treatment] use, or specific [antiretroviral treatment] combinations, could beneficially alter subsequent MS disease progression.”