Cognitive decline due to aging may set in much earlier than you think, a study recently published in the British Medical Journal reports.

For a while now, it has been generally accepted that cognitive decline in areas such as memory and mental function, does not begin to appear until we are in our 60s.

Researchers analyzed data from a study that began back in 1985, called the Whitehall II cohort study, which counted more than 10,000 British civil servants as its subjects.

Starting in 1997, as part of the Whitehall II study, researchers tested participants' memory, reasoning, vocabulary, and phonemic and semantic fluency, over the course of 10 years. At that time, there were almost 5,200 men and close to 2,200 women, ages 45 to 70 who participated in the cognitive testing.

The lead study author, Archana Singh-Manoux, research director at the French National Institute of Health and Medical Research in Paris, writes that a healthy lifestyle and good cardiovascular health are important when it comes to our cognitive health as we get older. And that for some risk factors, such as obesity, hypertension, and hypercholesterolaemia, it is mid-life levels that seem to be more important than those measured at older ages.

In their conclusion the study authors state the following:
"Determining the age window at which potential interventions are likely to be most beneficial is also a crucial next step."

Timing of onset of cognitive decline: results from Whitehall II prospective cohort study [BMJ]