Cardiovascular risk factors, such as smoking, obesity and high blood pressure “rot” the brain by damaging memory, learning and reasoning, according to a study published Nov. 26 in the journal Age and Ageing, by researchers from the prestigious university King’s College, London. The study builds on previous research which has also found a link between smoking and cognitive decline in older adults without dementia.
The researchers studied 8,800 people aged over 50, over a period of ten years and found that smoking had the greatest and most global negative effect on the brain and its function, with high blood pressure and obesity having a lesser effect. The mean age of participants at the 2004-05 survey was 67 and just over half (55%) of them were women.
Scientists warned that lifestyle choices can damage the mind as well as the body. Smoking in particular, as well as high blood pressure and obesity accelerated decline of memory, learning, attention and reasoning in older adults.
The study found that participants over the age of 50 who smoked, had high blood pressure or were most at risk of suffering a stroke, performed more poorly on a range of cognitive tasks designed to test memory recall, verbal fluency, attention and other cognitive outcomes.
The study aimed to assess three performance indicators: global cognition or overall mental ability, memory and executive function or decision-making ability. They found that those in the highest quartile of risk for a stroke according to the Framingham stroke risk score, had lower scores across all three cognitive outcomes more quickly, with deficits being apparent at the four-year follow-up appointment. High blood pressure, with the systolic blood pressure being 160 mmHg or higher was associated with lower global cognition and specific memory, but not until the eight-year follow-up appointment.
Smoking was consistently associated with lower performance on all three cognitive outcomes according to the study abstract,
The researchers analysed data on smoking, blood pressure, cholesterol levels and Body Mass Index (BMI), as well as Framingham cardiovascular and stroke risk scores (used to determine the probability of an individual developing heart disease or stroke within the next ten years).
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The researchers used data from the English Longitudinal Study of Ageing (ELSA) which is a prospective and nationally representative sample of people aged 50 and over residing in private households in England. This includes both objective and subjective data relating to health and disability, biological markers of disease, economic circumstance, social participation, networks and well-being. The survey data are designed to be used for the investigation of a broad set of topics relevant to understanding the ageing process.
The study is one of the few longitudinal investigations to explore the combined effect of multiple risk factors on cognitive decline in older adults. Researchers say these findings indicate that future clinical trials looking at cognitive decline should focus on the combination of these risk factors rather than individual triggers.
At four and eight-year follow-ups, participants undertook two measures of cognitive performance, including memory and executive functioning, which were then combined into athird, overall ‘cognitive index’ score. The memory task involved learning ten unrelated words before immediate and delayed recall was tested. For the assessment of executive functioning, participants were asked to name as many animals as possible in one minute, which examined verbal fluency, and to cross-through specified letters in a series (letter cancellation), which measured attention, mental speed and visual scanning.
The study showed that smoking had the most consistent impact, linked with lower cognitive performance in all three cognitive tasks after four years. Those with high BMI, blood pressure and stroke risk scores performed less well on cognitive tasks, although this varied across the three tests. High BMI was associated with lower performance on the memory task, high blood pressure was linked with lower scores for memory and overall cognitive performance, and those with a high risk of developing stroke were found to perform more poorly across all three cognitive assessments.
Dr Alex Dregan, Lecturer in Translational Epidemiology and Public Health at King’s College London, said: ‘Cognitive decline becomes more common with ageing and for an increasing number of people interferes with daily functioning and wellbeing. Some older people can become forgetful, have trouble remembering common words or have problems organising daily tasks more than others.
“We have identified a number of risk factors which could be associated with accelerated cognitive decline, all of which, could be modifiable. This offers valuable knowledge for future prevention and treatment interventions.”
The study was also one of the few longitudinal studies to explore cognitive decline over a long period of time in older adults, which is useful in identifying the short and long-term effects of cardiovascular risk factors.
High blood pressure was associated with lower performance on memory tasks and tests of overall cognitive ability after eight years, indicating that high blood pressure has a gradual impact over a longer period of time, as opposed to those with high stroke and cardiovascular risk, for whom the effect was more sudden (lower performance reported at four-year follow-up).
The researchers say this finding could be one reason why short-term trials may have failed to show effects of blood pressure lowering drugs on cognitive decline, as potential benefits may only emerge over substantial periods of time.
Dr Dregan believes the findings could serve as a basis on which to develop future clinical trials aimed at identifying interventions for the UK’s growing population of older adults. He said:
“Our research suggests that the most promising approach to delaying or preventing early ageing of the brain is one that acknowledges the multi-causality of cognitive decline. Thus, current efforts to reduce cardiovascular risk may prove beneficial for cognitive decline. One such initiative is the NHS Health Check programme, aimed at preventing cardiovascular disease by inviting 40-74 years olds to five-yearly check-ups in order to assess their risk of developing stroke, diabetes, kidney disease or heart disease, and to offer advice and support to help them manage that risk.”
Dregan, A. (2012-11-25) Cardiovascular risk factors and cognitive decline in adults aged 50 and over: a population-based cohort study. Age and Ageing, 9(7034), 994. DOI: 10.1093/ageing/afs166
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