Blood and saliva samples collected on the pilots' first visits allowed the Stanford investigators to genotype all 144 pilots, of whom 55 (38.2 percent) turned out to have at least one copy of a BDNF gene that contained the "met" variant. In their analysis, the researchers also corrected for pilots' degree of experience and the presence of certain other confounding genetic influences.
Inevitably, performance dropped in both groups. But the rate of decline in the "met" group was much steeper.
"We saw a doubling of the rate of decline in performance on the exam among met carriers during the first two years of follow-up," said Salehi.
About one-third of the pilots also underwent at least one round of magnetic resonance imaging over the course of a few years, allowing the scientists to measure the size of their hippocampi. "Although we found no significant correlation between age and hippocampal size in the non-met carriers, we did detect a significant inverse relationship between age and hippocampal size in the met carriers," Salehi said.
Salehi cautioned that the research covered only two years and that the findings need to be confirmed by following participants over a multiyear period. This is now being done, he added.
No known drugs exist that mimic BDNF's action in the brain, but there is one well-established way to get around that: Stay active. "The on
|Contact: Bruce Goldman|
Stanford University Medical Center