Drinking more than three cups of coffee a day may decrease a woman's rate of cognitive decline associated with age, but offers no such benefits for men, suggests a study.

A study, published in the journal Neurology, looked at 4,197 women and 2,820 men in France, and found that women who drank at least three cups a day had a 33 per cent lower decline in verbal retrieval and an 18 per cent lower decline in visuospatial memory, compared to those who drank one cup or less.

The effects were put down to caffeine, and are in line with the US average is more than three and a half cups. However, the average worldwide daily coffee consumption of one and a half cups.

"Caffeine is a psychostimulant which appears to reduce cognitive decline in women," said study author Karen Ritchie, of INSERM, the French National Institute for Health and Medical Research, in Montpellier, France.

"While we have some ideas as to how this works biologically, we need to have a better understanding of how caffeine affects the brain before we can start promoting caffeine intake as a way to reduce cognitive decline," she said.

"But the results are interesting - caffeine use is already widespread and it has fewer side effects than other treatments for cognitive decline, and it requires a relatively small amount for a beneficial effect," added Ritchie.

The researchers recruited the participants aged over 65 years or older from three French cities and measure cognitive performance at the start of the study and then again two and four years later.

After adjusting the results to take into account possible confounding factors, the researchers calculated that the benefits for women increased with age - coffee drinkers being 30 percent less likely to have memory decline at age 65 and rising to 70 percent less likely over age 80.

The occurrence of dementia was also recorded although coffee was not associated with any protection from dementia. "We really need a longer study to look at whether caffeine prevents dementia; it might be that caffeine could slow the dementia process rather than preventing it," said Ritchie.

Despite the association between caffeine and cognitive decline, Ritchie said it was unknown why there was a difference between men and women.

"Women may be more sensitive to the effects of caffeine," she said. "Their bodies may react differently to the stimulant, or they may metabolize caffeine differently."

"Further studies are required to ascertain whether caffeine may nonetheless be of potential use in prolonging the period of mild cognitive impairment in women prior to a diagnosis of dementia," concluded the researchers.

Coffee, one of the world's largest traded commodities produced in more than 60 countries and generating more than $70bn in retail sales a year, continues to spawn research and interest, and has been linked to reduced risks of certain diseases, especially of the liver and diabetes.

Source: Neurology