When Does the Brain Begin to Decline?
The brain begins to show signs of decline after a certain proportion of the nerve cells or neurons of which it is formed have died. A grown man has no more nerve cells than he did when he was born. These cells do not multiply as the body grows, as bone and skin cells do. Indeed, as a person grows older he has fewer and fewer nerve cells, because those destroyed are not replaced.
At the age of 70 or 80, as many as a quarter of the nerve cells may have died. That is the reason some old people cannot hear well or have poor memories. Yet others manage to retain their faculties and abilities until they are very old. Recent techniques have made it easier for scientists to study how our brains function, but there is still a great deal to discover.
According to a recent study our brains start to deteriorate from as young as 45 – 15 years earlier than previously thought. Memory, reasoning and comprehension skills – collectively known as cognitive function – all tend to get worse as we enter middle-age, found the study of thousands of Whitehall civil servants.
While full-blown dementia is usually confined to old age, the study adds weight to a growing body of evidence suggesting the disease can take decades to develop.
Writing in the online version of the British Medical Journal (bmj.com), the authors said that before their study there had been “little evidence of cognitive decline before the age of 60”. However, they noted the premiss that there was no actual mental decline pre-60 was “not universally accepted”.
The researchers quantified the mental abilities of over 7,000 civil servants between 1997 and 2007. Aged between 45 and 70 at the start, they were asked to undertake a series of tests at the beginning and end of the 10-year period. For example, in one test they were asked to recall as many words beginning with ‘S’ and as many animal names as possible from a list of words read to them. Other tests examined their vocabulary, aural and visual comprehension.
The researchers found those aged 45 to 49 in 1997 experienced a 3.6 per cent decline in cognitive function over the decade. Unsurprisingly, the researchers found mental decline gathered pace with age: those in their late 60s in 1997 saw their abilities decline by 8.5 per cent by 2007.
Although the research did not specifically look at participants’ general health, the authors noted that other studies had indicated that people with better cardiovascular health in middle aged tended to be less likely to develop dementia in old age. The academics, led by Archana Singh-Manoux from the Centre for Research in Epidemiology and Population Health in France and University College London, wrote: “There is emerging consensus that ‘what is good for our hearts is also good for our heads’.”
Commenting in bmj.com on the study, Francine Grodstein of the Brigham and Women’s Hospital in Boston, US, said: “This finding potentially has profound implications for prevention of dementia and public health.” As yet, there is no cure for dementia, and accumulating evidence indicates that effective interventions will need to be administered long before marked neurodegeneration has occurred.
“By pinpointing cognitive decline in younger adults, Singh-Manoux and colleagues have set a new benchmark for future research, and eventually clinical practice.” That is, efforts to prevent dementia may need to start in adults as young as 45 years.” In practice, that could mean earlier intervention in the form of lifestyle changes or drug treatment, to delay the threat of dementia in those most at risk.
Dr Anne Corbett, of the Alzheimer’s Society, said: “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.”