A GENE linked to IQ might also help to prolong life.
The gene codes for an enzyme called succinic semialdehyde dehydrogenase (SSADH), which destroys GABA, a neurotransmitter that dampens brain activity and causes drowsiness. The gene comes in two common forms: the so-called 鈥淭鈥� version is 20 per cent less efficient than the 鈥淐鈥� version. In previous studies, young people with two copies of the T version performed slightly worse on IQ tests.
SSADH also detoxifies the brain by getting rid of excess acid, helping to protect cells from the free-radical damage that accelerates ageing.
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So to study the effects of the gene on ageing and longevity, Giuseppe Passarino of the University of Calabria, Italy, and his colleagues took a representative sample of 514 Italians aged between 18 and 107 and identified which gene variants they carried. Of these they also evaluated 115 people aged 65 to 85 using a standard test of cognitive ability. As expected, those with two copies of the T version of the gene performed significantly worse on tests.
The team then used the ages and gene information to reconstruct a survival 鈥渟napshot鈥� for the entire group. Their model showed that people carrying two Ts were unlikely to live past the age of 85; the maximum age for those carrying at least one C copy was approximately 100 years (Annals of Human Genetics, ).
While those carrying two copies of the T gene certainly do decline faster in old age, it is not an early death sentence, Passarino says. 鈥淭here鈥檚 no doubt that lifestyle, such as reading, having challenging work and enriching your cultural life, is far more important than having the bad variant,鈥� he says.
鈥淭here is no doubt that lifestyle and having challenging work is far more important than having a bad gene variant鈥�
鈥淭he two associations taken together tell a good story,鈥� says Robert Plomin of the Institute of Psychiatry in London, who discovered the cognitive effects of the SSADH gene in 2004. 鈥淎lthough the sample size is small, with only 115 taking the test compared with the thousands expected in today鈥檚 studies, the reported associations with cognitive ability are significant and in line with our previous results,鈥� he says.
Plomin is less sure about the association with longevity because of the complicated estimation method used by the researchers. 鈥淏ut there are so many large studies of ageing populations that we鈥檒l soon know whether the T version is more frequent in short-lived people,鈥� he says.
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