Multiple Sclerosis, Risk of Passing It On

Multiple sclerosis and genetic risks
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Genetics plays a role in the risk of developing multiple sclerosis (MS), but the magnitude of that possibility has not been fully understood. Researchers have come to a better understanding in a new study in which they concluded that the risk of passing along the neurodegenerative disease is not as dire as once believed.

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Although more than 100 genes and associated genetic factors have been identified in relation to MS, environmental contributions (e.g., diet, pollutants, lifestyle, geography) also are being identified and evaluated. A better understanding of both genetics and environment are critical if we are to learn how to prevent, treat, and eventually cure this disease.

On the genetics front, a team of investigators at Karolinska Institutet evaluated data from population and health care registries that included information on more than 28,000 people with MS from 1968 plus matched healthy controls. In addition, the researchers had access to multigenerational data so they could conduct an extensive analysis that included relatives.

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Here’s what the new Swedish study uncovered:

  • The risk of MS developing in more than one sibling in a family was seven times higher when compared with the general population
  • The risk of a child developing MS if a parent had the disease was five times greater than the general population
  • There was no significant difference between mother or father in the risk of transmitting the disease to a daughter
  • Overall, the familial relative risks seem to be lower than reported in previous studies

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Previous studies
To get a perspective, it’s important to note that previous research into this area has indicated the following results. Since the information comes from different studies, the findings do not always agree.

  • Among identical twins, the risk of both developing the disease is 24 percent greater while the risk is 3 percent among non-identical twins.
  • Boys and girls whose mother has MS have 20 to 40 times the risk of developing the disease than children whose mother does not have the disease
  • One study indicated that women pass the disease to their children about twice as much as men with the disease, yet another study found the opposite: that men pass the condition twice as often

The bottom line
Based on the findings of the newest study, the authors concluded that “whereas multiple sclerosis is to a great extent an inherited trait, the familial relative risks may be lower than usually reported.” In addition to genetics, there are environmental factors regarding the risk of MS, such as vitamin D, smoking, alcohol use, latitude, and others that should be considered since they can be modified.

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References
Ebers GC et al. Parent-of-origin effect in multiple sclerosis: observations in half-siblings. Lancet 2004; 363:1773-74
Hansen T et al. Concordance for multiple sclerosis in Danish twins; an update of a nationwide study. Multiple Sclerosis 2005; 11:504-10
Kantarci OH et al. Men transmit MS more often to their children vs women: the Carter effect. Neurology 2006; 67:305-10
Sadovnick AD et al. Evidence for genetic basis of multiple sclerosis. The Canadian Collaborative Study Group. Lancet 1996; 347:1728-30
Westerlind H et al. Modest familial risks for multiple sclerosis: a registry-based study of the population of Sweden. Brain 2014 Jan 17 Epub ahead of print

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