Mono as Child or Teenager Tied to Risk of MS as Adult in Large Study

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by Marisa Wexler MS |

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People who contract infectious mononucleosis — colloquially known as “mono” — during childhood or adolescence are at a roughly two to three times greater risk of developing multiple sclerosis (MS) as adults, a large population-based study suggests.

Notably, the study points to mono itself — independent of other factors that may influence the disease’s development — as an MS risk factor.

The study, “Association of Infectious Mononucleosis in Childhood and Adolescence With Risk for a Subsequent Multiple Sclerosis Diagnosis Among Siblings,” was published in JAMA Network Open.

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Successive research suggests a link between early infections with the Epstein-Barr virus — the virus that causes mono — and an MS risk. However, these findings raise questions as to whether this perceived relationship is direct or indirect.

On one hand, it’s possible that the biological process of taking ill with mono helps to set the stage for MS. On the other hand, a number of factors that influence a person’s risk of developing mono — such as genetics and environmental exposures — could also influence their MS risk, without any direct relationship between the two diseases.

A team led by researchers in Sweden conducted an analysis of national databases in that country to gain clarity into this relationship. In total, the team assessed data covering almost 2.5 million people born in Sweden between Jan, 1, 1958, and Dec. 31, 1994.

Of this group, 26,954 (1.08%) had a recorded diagnosis of mono before age 25, and 5,867 (0.24%) were diagnosed with MS at age 20 or later; their mean age at diagnosis was 31.5.

Statistical analyses revealed a significant association between mono in early life and MS risk. Specifically, people who had mono in childhood (age 10 or younger) were about twice as likely to develop MS later on, while those who had mono as adolescents (ages 11–19) were about three times as likely.

To assess whether these relationships were due to the Epstein-Barr virus itself, or to other factors, the researchers looked at the relative risk of MS among siblings who did or did not have mono in their younger years. Essentially, the team reasoned that siblings are likely to have similar genetics and environments, so if there’s a significant difference in MS risk based on mono history, it’s likely that the virus itself is responsible.

Results suggested a link between mono and MS independent of familial factors, indicating that the association is indeed due to mono itself. The link remained significant after adjusting for potential confounding factors, such as sex, an MS diagnosis in either parent, order of birth, and age of mother and father at the time of birth.

Of note, the researchers initially identified a link between having mono in early adulthood (ages 20–24) and an increased risk of MS, but this association lost its statistical significance after familial factors — genetics and environment — were taken into account.

“The findings of this population-based cohort study suggest that IM [infectious mononucleosis] in childhood and particularly adolescence is associated with a subsequent MS diagnosis, independent of shared familial factors. Therefore, greater susceptibility to infection is less likely to be the explanation,” the researchers concluded.

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