A to Z of MS Risk of developing MS
In the general population in the UK, the risk of developing MS is about 1 in 700. Studies have shown that the risk is higher for people who already have someone with MS in their family. On average, the risk for first degree relatives (parents, children, siblings) of someone with MS is about 1 in 40. For second degree relatives (cousins, uncles/aunts, nephews/nieces) it is around 1 in 100.
MS is not hereditary. A hereditary condition is transmitted from parent to child or further generations, which is not the case in MS. One of the elements that combine to cause an individual to develop MS is a genetic susceptibility to the condition. As family members will share some of the same genes, this does mean that there is a higher risk of developing MS if there is already MS in the family. However, there is no certainty that the particular combination of genes that make a person in one generation susceptible will occur in subsequent generations. Many people diagnosed with MS do not have a family history of the condition.
Twins
Whilst the rate of MS within families suggests that there is a genetic factor involved in developing the condition, studies of identical twins show that genes are not the whole story. Identical twins have exactly the same genetic make up as each other. If MS were solely dependent on genes, it would be expected that if one identical twin developed the condition, so would the other. Studies have shown that rather than this 1 in 1 risk, the actual risk of developing MS for the identical twin of someone with MS is about 1 in 3.
MS risk in context
It is worth putting MS in context with other conditions.
- 1 in 3 people will develop some form of cancer
- 1 in 9 women will develop breast cancer at some point in their lives
- 1 in 9 men will develop prostate cancer
- 1 in 20 people over the age of 65 have dementia
- 1 in 22 people have chronic heart disease
- 1 in 33 people have diabetes
- 1 in 500 people have Parkinson's Disease
- 1 in 520 people in England and Wales have a stroke each year
Reference
Sadovnick AD, et al.
A population based study of multiple sclerosis in twins: update.
Annals of Neurology 1993;33:281-285.