The number of people with dementia is expected to increase dramatically as the population ages, which is why researchers from the Minnesota Evidence-based Practice Centre (EPC) wanted to analyse possible interventions for the disease.Findings from four systematic evidence reviews, published in the journal Annals of Internal Medicine, concluded that nothing seemed to be able to prevent dementia in patients who did not have it at the time.
For the first review, researchers looked at data from 16 trials comparing physical activity with inactivity.
They found insufficient evidence to be able to draw conclusions about the effectiveness of aerobic training, resistance training, or tai chi for improving cognition.
That said, they did find ‘low-strength’ evidence that combining different types of interventions at the same time – such as physical activity, diet and cognitive training – improved overall cognitive test performance.
The researchers also reviewed data from 51 trials comparing the effect of prescription medication on cognitive outcomes.
The evidence did not support the use of any of the studied pharmacologic treatments (dementia medications, antihypertensives, diabetes medications, NSAIDs or aspirin, hormones, and lipid-lowering agents) for cognitive protection.
A review of 11 trials of adults with either normal cognition or mild cognitive impairment at the time of enrollment found insufficient evidence that brain training exercises could prevent dementia.
Vitamins and supplements
Researchers reviewed 38 trials comparing over-the-counter (OTC) supplements, including omega-3 fatty acids, soy, ginkgo biloba, B vitamins, vitamin D plus calcium, vitamin C, beta carotene and multi-ingredient supplements.
They compared these with either a placebo supplement or other interventions for preventing or delaying cognitive decline, and found insufficient evidence to suggest that any of the supplements worked.
The researchers said the reasons why these interventions fail is not entirely clear. It is possible that they simply do not work to improve cognition, or it could be that the studies started the interventions too late in life or didn’t use them for long enough.
They noted that while there was no evidence about whether an intervention to practice a healthy lifestyle earlier in life protects against cognitive decline or dementia, it is unlikely to worsen cognition and may have other health benefits.
Commenting on the study, James Pickett, Head of Research at Alzheimer’s Society, told HuffPost UK: “There is no sure way to prevent dementia and, as these studies show, we have not yet found a successful way to reduce cases of the condition. However, studies looking at natural lifestyle differences like exercise, diet and smoking show that these factors do play a role in determining a person’s dementia risk.
“We need much more focus on research into reducing the risk of dementia if we are to develop intervention and prevention programmes that work.”