ACTRIMS 2023: HIV-positive people found to be less likely to develop MS

People infected with the human immunodeficiency virus (HIV) — including HIV-positive individuals who received antiretroviral treatment at some point after infection — are significantly less likely to develop multiple sclerosis (MS), a new analysis suggests. 

The decrease in MS risk was particularly pronounced among HIV-positive women. The findings suggest that HIV infection may protect against the development of the neurodegenerative disorder, particularly in female patients.

“There was a lower risk of MS among HIV individuals than expected [and] even when the HIV virus was suppressed we’re still seeing this reduced risk,” said Elaine Kingwell, PhD, a senior research associate at University College London, in a presentation at the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) annual forum, held in San Diego and virtually.

Kingwell provided data from the team’s analysis in an ACTRIMS talk titled “Risk of Multiple Sclerosis in People with HIV: An International Cohort study.”

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Decrease in MS risk especially pronounced in HIV-positive women

HIV is a virus that infects and destroys CD4-positive T-cells, a type of immune cell that has been implicated in the early development of MS. Theoretically, reduced amounts of these cells might mean that people with HIV are less likely to develop MS. However, there hasn’t been much research to explore the potential connection between the two diseases, and available studies were generally small and with conflicting results. 

To address that, an international team of researchers conducted an analysis using two large databases of HIV-positive people. One in Sweden was launched in 2001, while the other, from British Columbia (BC), in Canada, was started in 1992.

Collectively, the databases included information on nearly 30,000 people with HIV: 10,390 in Sweden and 18,773 in Canada. About three-quarters of the patients across the databases were men, and in both groups, the median age at initial HIV infection was in the mid-30s. The average follow-up time was nine years for the Canadian group and 10 years in the Swedish group. 

The analysis also included data from hospital administrative databases and MS registries in both countries, which were used to assess the risk of MS in the general population for comparison. 

“The objective of our study was to compare the risk of incident [newly diagnosed] MS in an international cohort of HIV-positive individuals and compare that to the general population,” Kingwell said.

Using statistical models that accounted for factors like age, calendar year, region of birth, and socioeconomic status, the researchers estimated that there should be 26.2 cases of MS among the HIV-positive group, assuming that people with HIV are at similar risk compared with the general population. However, only 14 actual cases of MS were recorded in the databases — about half of what would be expected. 

“This was similarly seen in the BC and Swedish data,” Kingwell said. 

The researchers also conducted an analysis using only data from HIV-positive patients who had ever been on antiretroviral therapy — medicines that can stop the HIV virus from replicating. Such treatments prevent disease symptoms and reduce the likelihood of transmission. About nine in 10 patients in the databases had been treated with antiretroviral therapy at some point post-HIV infection.

This analysis showed very similar results to the overall analysis: 12 MS cases were documented, compared with an expected number of 21.9 cases. That count represented a 45% reduction in the number of new cases.

“This large international study of two population-based [HIV-positive patient groups] shows a lower risk of MS among [HIV-positive] individuals, and [treated HIV-positive] individuals, than expected based on the risk in the general population,” the researchers wrote in their presentation poster.

There was a lower risk of MS among HIV individuals than expected [and] even when the HIV virus was suppressed we’re still seeing this reduced risk.

The reduction in MS risk among HIV-positive patients, overall and in the subset exposed to antiretroviral therapy, was seen in both men and women. However, the difference only reached statistical significance among women.

“As with any observational study, there were limitations and challenges to this study,” Kingwell said. “We were not able to estimate MS risk among the [antiretroviral therapy] unexposed HIV population, [and] we were unable to account for region of birth in Canada.”

Kingwell also noted as a limitation that the researchers could not measure undiagnosed MS.

“It is possible that our observations could be explained by underecognition of MS in the HIV cohorts. But … other diseases happen more frequently and are diagnosed more frequently [in HIV patients], so I would argue against that explanation,” she said.

Note: The Multiple Sclerosis News Today team is providing in-depth coverage of the ACTRIMS Forum 2023 Feb. 23–25. Go here to see the latest stories from the conference. Follow along on Facebook, Twitter, and Instagram for live updates using the hashtag #actrims2023.