Scientists have just discovered a new distinction between the brains of the two sexes: age-related changes to the brain occur more slowly in women than in men.
The brains of women are four years younger than men, and that difference occurs since early adulthood and lasts until old age, according to a study by researchers at the University of Washington.
The researchers found that healthy women have more lucid brains than men. In addition they uncovered that females live longer than males, and that their memories and mental strengths persist for a long time at old age.
This difference could be why women tend to stay mentally sharp for a longer duration than men, researchers said.
“We’re just starting to understand how various sex-related factors might affect the trajectory of brain ageing, and how that might influence the vulnerability of the brain to neurodegenerative diseases,” said neuroscientist Manu Goyal of the Mallinckrodt Institute of Radiology at Washington University School of Medicine in St Louis.
“Brain metabolism might help us understand some of the differences we see between men and women as they age,” added Goyal.
Scientists had already established that age-related grey matter volume decrease occurs more quickly in male brains than in female brains. It has also been demonstrated that gene expression in the brain changes more rapidly in ageing men than women, resulting in a reduced ability to build and break down molecules in the male brain.
These pieces of evidence are suggestive of a form of neoteny in the female brain, (assuming male brains as the baseline, which is something scientists do), but no one had looked at metabolism – how the brain runs on glucose – until now.
The scientists used a brain scanning technique called positron emission tomography to measure the flow of oxygen and glucose in the brains of 121 women and 84 men aged 20 to 82. The scans revealed how sugar was being turned into energy in different parts of the volunteers’ brains.
In babies and young children, a process called aerobic glycolysis is increased to grow and mature the developing brain. It is scaled down in adolescents and young adults, then drops steadily in older people until it reaches a very low level by the time people reach their 60s.