Scientist Stephen Hawking has motor neurone disease
Scientists have identified a protective gene that increases survival in motor neuron disease.
People with the KIFAP3 gene lived 14 months longer on average than other MND patients.
Experts hope they will be able to use this knowledge to develop life-extending treatments for patients with this debilitating and fatal disease.
So far, one drug, riluzole, has been proven to extend life expectancy, but only by a few months.
MND attacks the nerves that control movement and is often rapidly progressive.
The vast majority of people with MND die within two to five years. Half of people die within 14 months of diagnosis.
The researchers wanted to find out why a small minority appear to be more resistant to the disease.
To do this they looked at 300,000 genetic variants in 2,359 people with MND and 2,814 unaffected volunteers from six different countries.
They found that people with two beneficial variants of KIFAP3 lived on average four years while those with only one or none lived on average for two years and eight months.
This improved the chances of surviving five years from about 10% to more than 30% for those carrying the "good" variants of KIFAP3.
Lead researcher Professor Ammar Al-Chalabi, of King's College London, said scientists would now be able to work on designing new treatments based on KIFAP3.
"Treatments can now be directly designed to exploit the effect of this gene variation."
Researchers know that the gene is involved in a number of cellular processes, most notably the transport of essential molecules throughout the nerve cell.
Dr Brian Dickie, director of research development at the MND Association, called the findings "significant".
"This is the first gene to be associated with such a marked protective effect.
"Undoubtedly, this research will open up potential treatment strategies for the thousands of people living with MND in the UK and throughout the world."