A recent study found that concussions in adolescents can increase the risk of developing multiple sclerosis (MS) later in life. The risk increased substantially if the individual had suffered multiple head injuries as an adolescent.

What Causes MS?

Multiple Sclerosis is a disease of the central nervous system that “disrupts the flow of information within the brain, and between the brain and body.” Multiple sclerosis (MS) involves an immune-mediated process whereby the body’s immune system responds abnormally, targeting the central nervous system, including the brain, spinal cord, and optic nerves. Within the central nervous system, the immune system attacks myelin, the fatty substance that surrounds and insulates the nerve fibers, and the nerve fibers themselves. The damaged myelin forms scar tissue, which impacts and interrupts nerve impulses to and from the brain and spinal cord.

The cause or causes of MS are uncertain but it is believed that the disease is triggered by an environmental factor or factors in a person who is genetically susceptible. The study identified concussion in adolescence as a risk factor.

The Impact of Concussions

In the study, researchers divided the subjects into two groups – children 10 and under and adolescents between ages 11 and 20.

Individuals who had experienced a concussion between the ages of 11 and 20 were approximately 22 percent more likely to later develop MS than those who had not had a brain injury. The risk doubled if the individual had sustained multiple concussions between the ages of 11 and 20.

However, concussions experienced among children 10 and under, did not contribute to a greater risk of MS later in life.

The study found that brain injuries occurring during adolescence, particularly multiple brain injuries, is associated with a raised risk of MS. This may be attributed to triggering an autoimmune process in the central nervous system.

How Was the Study Conducted?

In the study, conducted in Sweden and published in the Annals of Neurology, researchers examined the medical histories of every person in Sweden who was diagnosed multiple sclerosis diagnosis between 1964 and 2012. Sweden keeps extensive health databases from which the data was drawn.

Each of the 7,292 men and women who had been given MS diagnoses were matched with 10 other Swedes who shared their age, gender, and county of residence. The scientist thus analyzed data involving more than 80,000 people. Finally, the researchers looked into whether any of these individuals had gone to a hospital for treatment of a concussion or broken bone when they were young. The researchers included the information about broken bones because the symptoms of MS may include stumbling or falling, and may begin years before diagnosis. They examined bone injuries to assess the possibility of reverse causation, which was not found to be an issue.

The study was observational, meaning that it can link concussions in youth to a greater risk for MS, but not prove that one causes the other.

Concussions Among Youth in the United States

In the United States, the results of the Sweden study linking MS and concussions underscore the importance of recent efforts to enact and implement laws to address concussions occurring during participation in youth sports which carry the risk of brain injury.