It's all downhill for the brain once you reach 40, according to a new US study. Scientists at Harvard Medical School have identified a set of brain genes that do not work as well after this age, and another set that work harder, to try and limit the effects of this damage. Their findings, published online in the journal Nature, suggest that brain ageing begins in early middle age, and that the process is triggered by damaged DNA. Study leader Bruce Yankner says the study shows that there is 'a genetic signature' of the ageing process, adding 'we can now work to determine how that impacts brain function'.
The researchers studied post mortem brain tissue from 30 people, ranging in age from 26 to 106, and looked at the activity of 11,000 different genes. They identified 180 genes that do not make as much protein in older brains as they do in tissue taken from those under 40. The set of damaged genes include about 20 known to make proteins involved in learning, memory and other brain functions. It seems that the damage occurs in 'promotor' regions of the genes - sections of DNA that control when, where and how much a gene is switched on.
The team also identified another set of genes that differ between old and young brains, which appear to increase, rather than decrease in activity. These genes make proteins that repair damaged DNA, which have to work harder as the brain ages. 'One potential scenario is that we all go through this degenerative change, but how the brain compensates differs from individual to individual and may determine individual outcomes', said Yankner.
Future work could shed light on age-related brain diseases such as Alzheimer's and Parkinson's disease, and might lead to new treatments for these disorders. Yankner's team found that by genetically altering ageing brain cells growing in the laboratory, they could 'fix' the damaged genes, and restore their activity. Whilst he stresses that new therapies are some way off, Yankner thinks that 'the process of maintaining the integrity of the genome is going to be very important in understanding the ageing process'.
Sources and References
The Brain Starts to Change at Age 40
Genetic Changes May Explain Brain Decline
Some brains are old at 40
The Brain May Start to Age at 40 Years