Cognitive decline can begin by 45

6th January 2012 - Life may be said to begin at 40 but if the experts are to be believed cognitive decline can begin just a few years later at the age of 45.

The brain’s capacity for memory, reasoning and comprehension skills can start to deteriorate from middle age according to research published on bmj.com.

Previous studies have suggested cognitive decline does not begin before the age of 60, but it's not a universally accepted viewpoint and this latest research suggests it's not correct.

Research

Led by Archana Singh-Manoux from University College London and the Centre for Research in Epidemiology and Population Health in France, researchers observed 5,198 men and 2,192 women over a 10-year period from 1997. They were all civil servants in London aged between 45 and 70 and were part of the Whitehall II cohort study established in 1985.

Participants’ cognitive functions were assessed three times over the study period. Individuals were tested for memory, vocabulary and aural and visual comprehension skills. These included recalling in writing as many words beginning with “S” (phonemic fluency) and as many animal names (semantic fluency) as possible.

Results

After differences in education level were taken into account the results showed that cognitive scores declined in all categories (memory, reasoning, phonemic and semantic fluency) except vocabulary and there was faster decline in older people.

The findings also reveal that over the 10-year study period there was a 3.6% decline in mental reasoning in men aged 45-49 and a 9.6% decline in those aged 65-70. The corresponding figures for women were 3.6% and 7.4%.

Why it's important

The authors say it's important to investigate the age at which cognitive decline begins because medical interventions are more likely to work when individuals first start to experience mental impairment.

They argue their findings demonstrate the importance of promoting healthy lifestyles, particularly cardiovascular health, as there is emerging evidence that “what is good for our hearts is also good for our heads.”

They add that targeting patients who suffer from one or more risk factors for heart disease (obesity, high blood pressure and high cholesterol levels) could not only protect their hearts but also safeguard them from dementia in later life.

In an accompanying editorial, Francine Grodstein, Associate Professor of Medicine at Brigham and Women’s Hospital in Boston US, says the study “has profound implications for prevention of dementia and public health.”

She adds that more creative research, perhaps using telephone and computer cognitive assessments, needs to be undertaken.

Reaction

Reacting to the study in a statement, Dr Anne Corbett, research manager for the Alzheimer's Society, says: "This large, important study adds vital information to the debate over when cognitive decline begins. However, the study does not tell us whether any of these people went on to develop dementia, nor how feasible it would be for GPs to detect these early changes.

"More research is now needed to help us fully understand how measurable changes in the brain can help us improve diagnosis of dementia. An early diagnosis is essential as it can provide access to support and potential treatments which can vastly improve people’s quality of life."

Dr Simon Ridley, head of research at Alzheimer’s Research UK, said in a statement: "Experts believe that Alzheimer’s disease, the most common cause of dementia, begins to develop in mid-life. Although this study didn’t look at dementia, it would be important to follow up these participants to see which people go on to develop the condition. It’s important to note that the group studied here was not representative of the population as a whole, and it would be helpful to see similar studies carried out in a wider sample."