Monday, June 30, 2008

Which Cognitive Enhancers Really Work: Brain Training, Drugs, Vitamins, Meditation or Exercise?

Although wisdom may come with age, our brains don't get any faster. Many areas of cognitive function decline over time: attention wavers, processing speed decreases, memory starts to crumble.

All kinds of methods for fighting back against this brain-wide slow-down have been suggested. There is training with computer programs, popping pills, taking nutritional supplements, meditating or even getting some more exercise.

Some want to ward off the scourge of a rapidly ageing population: dementia. Others are looking for competitive advantage against younger, faster brains.

So: what to choose? These methods, along with many others, are often presented as though they're all roughly equivalent, but this isn't true. The scientific evidence currently available is much stronger for some of these options than others.

This post examines what the research currently tells us about each method for cognitive enhancement and delivers a verdict on each.

1. Brain training
Computer programs that promise to improve cognitive function have become all the rage in recent years, mostly on the back of the success of Nintendo's 'Brain Age' game. Many other companies have now jumped on the bandwagon and the market for brain fitness software
reached $225 million in the US in 2007 according to a report from SharpBrains.

But what about the science behind the hype?
Certainly cognitive training has been shown to be effective in a few randomised controlled trials, but the evidence is still quite limited. The first large study in older adults without dementia failed to find an improvement in daily functioning from the training,
but it did slow decline. Also, this study's method has been criticised.

Other studies have found benefits for specific groups such as children with attention deficit hyperactivity disorder (ADHD) and dyslexia. Whether advantages gained by these groups might be effective for others is a matter for debate.

The real challenge for brain training is showing that practising one type of mental skill transfers over into other real-life benefits. Doing puzzles like Sudoku or completing crosswords probably only improves your performance on those specific tasks.

One new study, though, does suggest that training working memory can increase fluid intelligence - what we use to solve problems which don't rely on things we already know. The study, recently published in The Proceedings of the National Academy of Sciences, found that
gains in fluid intelligence were proportional to the amount of working memory training completed.

Unfortunately this is still early-stage exploratory research and many are not convinced that the actual products available on the market are beneficial. Sandra Aamodt, the editor in chief of Nature Neuroscience and Sam Wang, a Princeton University molecular biologist explain in the New York Times:

"In the United States, consumers are expected to spend $80 million this year on brain exercise products, up from $2 million in 2005. Advertising for these products often emphasizes the claim that they are designed by scientists or based on scientific research. To be charitable, we might call them inspired by science -- not to be confused with actually proven by science."

It's telling that the best-selling brain training software - Nintendo's 'Brain Age' - has the lowest level of clinical validation according to a market report from Sharp Brains.

Verdict: Evidence for the benefits of cognitive training for everyday functioning is still very limited. Brain training software currently available is mostly 'inspired by science' rather than based on it. Treat marketers' claims with extreme scepticism. Side-effects are probably limited to repetitive strain injury and a depleted wallet.

2. Drugs
Until recently the main chemical cognitive enhancer most people used was caffeine. But there are a whole batch of new drugs that could challenge caffeine's dominance as the safe stimulant of choice. Of these, two well-known for their 'off-label' use are Modafinil (also known as Provigil) and Ritalin..........

Verdict: Amongst the chemical cognitive enhancers Modafinil is currently fashionable for grown-ups. But is it really that much better than caffeine? This study and this study suggest that in warding off sleep Modafinil is no more effective than caffeine - and caffeine is legal and readily available. Probably better to stick to tea or coffee.

3. Nutritional supplements
There are all kinds of claims for the abilities of nutritional supplements to enhance cognition. For example, vitamin B6 has been found to enhance memory (but far from conclusively) and there are many other claims being made by marketers for vitamins E, B12, folate, neurosteroids and so on.

However, in reviewing the research the Academy of Medical Sciences points out that most of the studies are few, far between and small in scope.

Verdict: Unproven, but probably not dangerous as long as you're not exceeding the recommended daily allowances. On the downside supplements can be costly.

4. Meditation...........

Verdict: Meditation still has to be considered unproven as a cognitive enhancer but it probably won't do you any harm, plus it's free.

5. Exercise
Whether you're old or young, fit or even suffering from a neurodegenerative disorder, aerobic exercise has been found to be beneficial for cognitive health. Randomised controlled trials, along with reviews of many of these trials (such as this one in Neuromolecular Medicine), have shown that exercise improves cognitive function across the board. It has also been found to be particularly good at enhancing executive control processes (e.g. planning and working memory).

Exercise is also thought to encourage the growth of new brain cells. In the past scientists always thought that neurogenesis - growing new brain cells - was impossible in humans. New studies, though, have shown that we can grow new brain cells.

Research reviewed in Neuromolecular Medicine suggests physical exercise can promote neurogenesis in the hippocampus - an area of the brain thought to be important in memory and learning.

Verdict: The evidence for exercise boosting cognitive function is head-and-shoulders above that for brain training, drugs, nutritional supplements and meditation. Scientifically, on the current evidence, exercise is the best way to enhance your cognitive function. And as for its side-effects: yes there is the chance of an injury but exercise can also reduce weight, lower the chance of dementia, improve mood and lead to a longer life-span. Damn those side-effects!

The results are in (for now)

Even though exercise is the current winner for enhancing cognition, this might change in the future. Maybe better drugs for enhancing brain function will be developed - possibly en route to improved treatments for conditions like Alzheimer's. Or maybe studies on nutritional supplements, brain training software or particular forms of meditation may provide firmer evidence.

On current evidence exercise is clearly the best method for increasing useful everyday cognitive functioning. And in the future we may even have exercise regimes that are specifically targeted at enhancing cognitive function.

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