How Families Share MS Risk Factors

Multiple sclerosis familial risks lower than previously reported

(RxWiki News) Multiple sclerosis — a disease that affects the central nervous system — can cluster in families. How important family history is in the development of the disease was assessed in a recent study.

Swedish researchers discovered that family risks for multiple sclerosis (MS) were lower than previous research suggested.

Compared to the general population, siblings of individuals with MS had a seven times higher risk of being diagnosed with the disease, and children of affected parents had five times higher risks.

"Make sure your doctor knows your family’s medical history."

Led by Helga Westerlind, PhD student in the Department of Clinical Neuroscience at the Karolinska Institutet in Stockholm, Sweden, these researchers combed through several Swedish databases to examine familial risk factors in MS.

MS is a central nervous system disease that causes problems with muscle control and strength, vision, balance, feeling and thinking. The World Health Organization estimates that roughly 2.5 million people in the world have MS.

The disease is not directly inherited, but the genes a person has play an important role in the development of MS. According to National Multiple Sclerosis Society, about one out of every 750 people in the general population develops MS. Among close relatives (parents, children, siblings), the risk is higher — one in 40 people.

This study looked at the probability of a relative transmitting genes associated with MS to a family member. All types of family relationships were explored.

Sweden’s Multi-Generational Registry was used to identify first- and second-degree relatives and cousins. First-degree relatives include parents, children and siblings, and second-degree relatives are grandparents and grandchildren, aunts and uncles, nieces and nephews and half-siblings.

Data from Swedish Multiple Sclerosis Registry and the National Inpatient Register and Stockholm Registries found a total of 28,396 individuals living with MS since 1968.

The average age of disease onset in this group was 33.7 years.

The researchers also randomly selected people without MS and their relatives as controls to compare the risks of passing along the disease in families with and without MS.

Westerlind and colleagues uncovered a number of interesting trends:

  • Siblings of people with MS had a seven times higher risk of developing the disease than controls.
  • The children of MS patients had five times higher risks of being diagnosed with MS than the general population.
  • There was no increase in risk among grandchildren and nieces/nephews.
  • A father with MS was more likely to transmit the disease onto his son than onto his daughter.

“In summary, whereas multiple sclerosis is to a great extent an inherited trait, the familial relative risks may be lower than usually reported,” the researchers wrote.

This study was published in the January issue of Brain.

This study was supported by grants from The Swedish research council, Karolinska Institutet, Stockholm County Council, the Jensen foundation and Swedish Research Council for Health, Working Life and Welfare.

Review Date: 
February 7, 2014