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The ageing brain

By Dr Alex Dregan

Do vascular risk factors such as high blood pressure and smoking make us forgetful?

As our bodies start to show the signs of ageing, our brain is naturally ageing too. But some older people can become forgetful and have trouble remembering common words or organising daily activities more than others. There are few proven interventions to prevent this kind of cognitive decline in older adults, although treating modifiable risk factors for vascular disease and stroke, such as cholesterol and body mass index (BMI), has been suggested as a promising approach to preventing or delaying cognitive impairment for a growing UK population of older adults. So is there a link between high blood pressure and forgetfulness?

Despite much recent interest, studies to date have reported inconsistent relationships between blood pressure and cognitive functioning. Evidence suggests that people diagnosed with high blood pressure levels tend to perform more poorly on most domains of cognitive functioning, including memory, learning, attention, and reasoning. However, clinical trials have so far failed to demonstrate that antihypertensive drugs used to lower or control high blood pressure levels are effective in preventing cognitive decline in older adults.  This inconsistent evidence poses a challenge when developing recommendations for the prevention of cognitive ageing.

Cognitive ageing, such as symptoms of forgetfulness, is increasingly seen as the result of the joint effect of several vascular disease risk factors, including high blood pressure, BMI, cholesterol levels, and smoking. However,  the combined influence of these on cognitive decline is less commonly explored among older adults at increased risk of both cardiovascular disease and cognitive decline.

In a recent paper, we looked at Framingham stroke and cardiovascular risk scores (a measure used to assess an individual’s probability of developing stroke or cardiovascular disease over a 10-years period) and investigated their association with cognitive decline in older adults. The study included over 8,000 adults aged 50+ living in private households in England. Participants with the highest risk of future stroke or cardiovascular events, based on their risk factors values, were found to perform more poorly on tests of memory and executive functioning after a four year period. This adds weight to the theory that the combined effects of risk factors for vascular disease and stroke may be associated with more rapid cognitive decline in older adults. In other words, those at greater risk of cardiovascular problems were likely to experience a more rapid onset of symptoms associated with cognitive decline, such as forgetfulness.

We believe that these findings support the need for a multifaceted approach when seeking to prevent cognitive decline. The main implication of this is the need for addressing the combined effect of multiple risk factors, including lowering high blood pressure and high cholesterol levels, weight loss, and stopping smoking. Thus, healthcare professionals should encourage older people to adopt healthy lifestyles that would include stopping smoking and increased exercise (as well as improved diet not investigated here) and taking prescribed medicines aimed at controlling high blood pressure and high cholesterol levels. Such recommendations could potentially prevent or delay future declining memory or reasoning capacities in older adults, particularly those in higher risk groups.

The results also suggest that a harmful effect of high blood pressure on memory or reasoning abilities may develop over a prolonged period of time. This may be one reason why short-term trials have failed to show a consistent benefit from antihypertensive treatment on cognitive decline. For instance, since the negative impact of high blood pressure on memory or reasoning abilities takes place over a prolonged period of time, short-term treatment may not be sufficient to reverse or delay its adverse influence. Therefore, we would expect that any potential cognitive benefits from lowering blood pressure may only be observed over substantial periods of time.

These new results suggest that attention to the combined effects of multiple vascular risk factors may hold some promise as a strategy to prevent cognitive decline in older adults.

Dr Alex Dregan is a Lecturer in Translational Epidemiology within the NIHR Biomedical Research Centre at the Guy’s and St Thomas’ NHS Trust and King’s College London. He trained in Public health at the Institute of Education, University of London. His research interests are in translational epidemiology research as applied to public health. He is co-author of the paper Cardiovascular risk factors and cognitive decline in adults aged 50 and over: a population-based cohort study for the Age and Ageing journal,  and this has been made freely available for a limited time.

Age and Ageing is an international journal publishing refereed original articles and commissioned reviews on geriatric medicine and gerontology. Its range includes research on ageing and clinical, epidemiological, and psychological aspects of later life.

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