Men and women with multiple sclerosis equally transmit the genetic risk of the disease to their children, concludes a Canadian study published in Neurology, the medical journal of the American Academy of Neurology.
The research contradicts results of a recent study that found fathers were more likely than mothers to transmit the risk of developing MS to their children.
Researchers studied 3,088 Canadian families with one parent affected with MS.
Of the 8,401 children in those families, 798 had MS. The study found equal transmission of the genetic risk of MS to children, with 9.41 per cent of fathers transmitting MS to their children compared to 9.76 per cent of mothers.
"We also found there were equal numbers of daughters and sons receiving the genetic risk of the disease from their parents," said study author Dr. George Ebers from the University of Oxford.
"Intriguingly, we also found when half-siblings both have MS, there is a clear maternal effect, with mothers much more likely to be the common parent."
Ebers says the findings show no evidence of "the Carter effect," which was recently cited in a study that found men with MS were twice as likely to pass the risk of disease on to their children. According to the Carter effect, men are more resistant to MS because they carry a higher genetic load and thus are more likely to transmit the genetic risk of the disease to their children.
"Our study involved 16 times as many people as the previous published study. It casts further doubt on the widely believed multiple gene mode of inheritance of susceptibility to MS," said Ebers.
Canada has among the highest rates of multiple sclerosis in the world, as do many nations in northern Europe. That has prompted speculation genetics and geography may increase the risk for people who live in countries far from the equator.
A study last year by Dr. Ebers found that women with multiple sclerosis now outnumber men in Canada by a ratio of more than three to one. They also found that this gender ratio has been rising for at least 50 years.
Multiple sclerosis is an unpredictable disease caused by inflammation and patchy destruction of the protective myelin covering the central nervous system. Those with the progressive disease tend to go through sporadic periods of attack followed by recovery.
As the disease develops, sufferers may experience a range of symptoms, including extreme fatigue, balance and co-ordination problems, muscle stiffness and weakness, and speech and cognitive difficulties.
