September 7, 2021
Summary: A new study links viral infections including mononucleosis and pneumonia experienced during adolescence with an increased risk of developing multiple sclerosis.
Source: The Conversation
Multiple sclerosis (MS) is most often diagnosed between the ages of 20 and 50. Certain genes put a person at greater risk of getting this disease of the central nervous system, but scientists are still trying to understand the triggers.
My colleagues and I have been studying these triggers for many years. Our earlier research found that pneumonia in adolescence is associated with a raised risk of MS, so we decided to investigate whether other types of infection are associated with the condition.
We had to be careful, though, because infections can be a consequence of MS rather than the other way around. Also, it can be five to ten years, or even longer, between the disease process starting and a person showing the first symptoms, which include numbness and tingling, stiffness, difficulty with balance, vision problems and fatigue. We therefore had to take extra steps to be certain that the infections occurred before any MS-related disease became apparent.
For our study, published in the journal Brain, we used the health records of nearly 2.5 million people born in Sweden between 1970 and 1994. Just over 4,000 of them were diagnosed with MS after the age of 20. Among this group, 19% had had an infection diagnosed in hospital between birth and ten years of age, and 14% between ages 11 and 19.
We found that most infections before age 11 were not associated with a later MS diagnosis. In contrast, infections diagnosed in a hospital (indicating they are relatively severe) between ages 11 and 19 were consistently associated with a raised risk of developing MS.
Not all types of infection were associated with subsequent MS, but a striking finding is that infections of the central nervous system (the brain and spinal cord) increased MS risk most notably. This makes sense, as we believe that inflammation in the central nervous system can start the autoimmune process (when a person’s immune system attacks part of their body) that causes MS.
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