The work, by Dr Angus MacDonald at Heriot-Watt University, Edinburgh, is the first to provide concrete mathematical data about the real effects of genes on life expectancy. Contrary to expectations, the research suggests that our growing understanding of the role of genes in illness will not create a "genetic underclass".
"The sort of increase in the chances of dying each year from a genetic illness is about 10 per cent over the average. That would be lost in the `noise' of life insurers' statistics," said Dr MacDonald, speaking at the British Association in Sheffield.
Premiums generally only rise for people whose chances of dying are between 30 and 50 per cent higher each year than the average - such as heavy smokers or the seriously overweight.
By contrast, genes that cause breast or other cancers have a far smaller impact on the likelihood of dying. Similarly, long-term care for the 2 per cent of the population who have two copies of a gene called ApoE4 - meaning they are more likely to develop Alzheimer's disease - would cost between 10 and 30 per cent more than average.
That too would be "borderline" for raised premiums in present circumstances, said Dr MacDonald.
Insurers had feared that such genes would have a severe effect on mortality and costs, and that they would be caught out by people applying for assurance while knowing that they posed a high risk.
Only threats from the Government in 1995 dissuaded companies from demanding to be allowed to ask for tests for certain genes before issuing assurance. The life assurance industry reluctantly agreed a code of conduct, which excludes demands for gene tests where the payout would be less than pounds 100,000.
But Dr MacDonald, who used a mathematical modelling technique called "Markov multiple state models", said assurance companies' fears were overblown. "Genetic testing will not create a new genetic underclass.
But there already is one, consisting of the people with a strong family history of breast cancer or Huntington's disease." Such people have to disclose their family's history of illness when applying for cover. That information did not count as genetic testing, he said.
However, his conclusions would not apply for health insurance companies, where the entire system of premiums is much more sensitive to small changes in the risk of illness. In the US, where everyone must have personal health insurance, genetic predisposition to illness is "a significantly greater problem", Dr MacDonald said.Reuse content