Study looks at reducing dementia

“Keeping one's brain active, trying not to become depressed and eating a diet rich in fruit and vegetables are the best ways to ward off developing dementia,” according to a report in The Daily Telegraph.

This study was set up to estimate how eliminating specific risk factors for dementia could reduce the number of people developing the condition. The researchers followed 1,433 elderly adults over seven years, during which they regularly assessed cognitive performance and several known and suspected risk factors for dementia.

This relatively large, well-conducted study may have implications for public health programmes. The conclusions are only rough estimates and their relevance to individuals is unclear. Little is known about whether any of these risk factors might help to cause the development of dementia. Furthermore, the participants were, on average, 72.5 years old at the start, and the effect of modifying these risk factors earlier in life is unknown.

The message is a good one however, and eating a healthy diet, keeping the brain and body active and maintaining emotional wellbeing are all sensible measures. Although the exact cause of dementia is unknown at present, it is possible, but not proven, that altering your lifestyle accordingly may reduce the risk of developing this condition.

Where did the story come from?

The study was carried out by researchers from La Colombiére Hospital, Montpellier, the University of Montpellier and Imperial College in London. It was funded by Novartis, a pharmaceutical company, and by the National Research Agency. The study was published in the peer-reviewed British Medical Journal.

The study was reported fairly in the media, although many papers tended to interpret the findings to give advice on what individuals can do to ward off dementia. While the advice is sensible, the research focused on what might be done at a public health level to reduce cases of dementia in the future. Whether their estimates can be translated into reductions in individual risk is unclear.

What kind of research was this?

This prospective seven-year cohort study was set up to estimate how eliminating specific risk factors for dementia could reduce the number of people getting the condition. Although the exact cause of dementia remains unknown, several modifiable risk factors have been identified, including heart disease and stroke, diet, depression, alcohol and educational level. The researchers point out that the world is facing a dementia “pandemic”, with predicted increases of between 100%–300% between 2001 and 2020. Even small reductions in incidence will have enormous benefits for public health.

What did the research involve?

In the first step of the study, researchers looked at all the risk factors for dementia identified in previous studies. These include age, education, ethnic differences, genetic factors, a history of depression, and lifestyle factors such as diet, alcohol and caffeine consumption. They then identified a list of “candidate” risk factors that could potentially be modified or reversed, which they planned to use in modelling the effects of any intervention.

In the second step, 1,433 healthy people over 65 were recruited and drawn at random from the electoral rolls of Montpellier in the south of France between 1999 and 2001. All the participants had detailed, validated cognitive testing by a neurologist at the start of the study period and again at two, four and seven years. At the start of the study, they also took part in detailed interviews with questions on social and economic status, educational level and an adult reading test that is recognised as a measure of lifetime intelligence. Questions were also asked about income, neighbourhood, height, weight, diet, alcohol consumption, tobacco use and coffee and tea intake.

Participants were also asked detailed questions about their medical history, including vascular factors such as whether they had experienced either heart disease or a stroke. Any reports of vascular problems were confirmed by doctors and medical records. Other areas included depression (using validated scales), medication use, blood pressure, diabetes and BMI.

The researchers used standard statistical methods to assess any association between the development of dementia or mild cognitive impairment (an established predictor for dementia) and the “candidate” risk factors. They then used these findings to estimate what impact eliminating certain risk factors at the population level would have on the future incidence of dementia.

What were the basic results?

The principal findings from the seven-year study were that:

The population attributable percentage of the main known genetic risk factor for dementia (carrying a certain type of the apolipoprotein E gene) was 7.1% (i.e. there would be a 7.1% reduction in cases of dementia if this genetic predisposition could be eliminated).
Likewise, increasing cognitive activity levels (as measured by reading scores that gave a measure of general intelligence) would reduce cases of dementia by 18.1%.
Eliminating depression from the elderly population would reduce dementia cases by 10.3%.
Eliminating diabetes would reduce dementia cases by 4.9%.
Increasing fruit and vegetable consumption among the population would reduce dementia cases by 6.5%.
Overall, eliminating depression, diabetes and increasing fruit and vegetable consumption would reduce dementia cases by 20.7%.

How did the researchers interpret the results?

The researchers conclude that in the absence of effective treatment, public health programmes should, above all, aim to prevent diabetes, already a well-established risk factor for dementia. While improving diet and intellectual activity would also help, these are difficult strategies to implement at a population level. Whether depression is a risk factor or an early symptom of dementia is unclear, but the researchers say it would be easy to screen for and treat clinical depression.

Conclusion

This well-conducted, prospective study is a useful contribution to the understanding of the role that certain risk factors play in the development of dementia. Its diagnoses of dementia were validated by neurologists and it also includes measures of almost all known modifiable risk factors. It supports the results of previous research showing that these are risk factors, and estimates how much future dementia incidence could be reduced if certain risk factors were tackled at a public health level. However, as the researchers note, their calculations can only provide crude estimates.

The study had other limitations, outlined below.

Although no one had been diagnosed with dementia at the start of the study, it is still difficult to be sure that all of the risk factors definitely preceded any cognitive changes.
All the participants were over 65 at the start of the seven years and the average age was 72.5 years. Therefore, it is difficult to determine what effect modifying these risk factors earlier in life would have on the risk of later developing cognitive impairment and dementia.
The researchers included in their analysis people with mild cognitive impairment within the group who developed dementia, even though some of these may never develop dementia.
It is unclear how far the risk factors measured are interdependent, i.e. how eliminating one would also modify another.
Although the researchers adjusted their findings for other factors that may affect risk of dementia, it is not possible to know for sure whether other things could be influencing an individual’s risk.

Overall, this study cannot definitively establish a causative link between dementia and these risk factors. Nevertheless, eating a healthy diet, keeping the brain and body active and maintaining emotional wellbeing are all sensible measures towards promoting a healthy life.