Life begins at middle age? Not for your brain

If you have hit the magic age of 40, chances are that your brain has started packing up.

Genetic researchers in Boston have discovered that mental faculties begin a gradual decline in many people aged 40 and above. Their research offers insights that could be useful in treating Alzheimer's disease and other cognitive disorders.

The study, which the the research team led by Bruce Yankner of Children's Hospital and Harvard Medical School in Boston, Massachusetts, published in the journal Nature, also throws up new knowledge on ageing, especially on how some individuals age before others. 

Studying post-mortem brain samples taken from 30 people aged between 26 and 30, Yankner's team looked at the patterns in which about 11,000 genes were turned on or off in brains of various ages. The objective: to see how the ageing process kicked in.

After age 40, nearly 400 genes showed significant changes in activity. Several were damaged and appeared to show faulty functioning. Though the team could not pinpoint exactly which mental faculties were affected or had started to decline as a result of the damage, it believes it has leading evidence that most of these genes are involved in learning, memory and brain-cell-to-brain-cell communication.

In contrast, some genes show heightened activity after age 40. The researchers believe this could be to

compensate for the damage caused by the decline of other genes. 'Genes which play a role in learning and memory were among those most significantly reduced in the ageing human cortex,' Yanker was quoted as saying. He added that these genes included those required for communication between neurons. 

'This gives us a starting point because what we've shown is that there's a genetic signature, so to speak, of this ageing process and now we can work to determine how it impacts brain function,' he said.

The team observed compelling similarities in gene expression patterns in adults aged 40 and above. This suggests that the process of ageing had not yet inflicted significant damage. In people aged over 70, the genes functioned in a similar manner, perhaps showing that ageing takes a uniform toll by then. Between these two ages, however, there was a wide-ranging variation, which probably shows that brain function declines at different rates in individuals aged between 40 and 70. As to why this happens, the researchers have no answer yet.

'When ageing begins and what triggers its onset is one of the major conundrums of biology,' Yankner said.

On the flipside, the study may add a whole new dimension to the notion that life begins at middle age.

'Individuals may diverge in their rates of ageing through middle age, approaching a state of 'old age' at different rates,' the professor added. 'It will be of interest to investigate this relationship in different populations and demographic groups.'