Rude awakenings

LACK of sleep: it creeps up from middle age and leaves you exhausted. We assume our lifestyles are to blame.

LACK of sleep: it creeps up from middle age and leaves you exhausted. We assume our lifestyles are to blame. Most of us drink too much and relax too little, stressed out with work and time-crunched by commitments to kids and family, leaving little time for quality sleep.

But recently scientists at the University of California, Berkeley, suggested that our busy lives were not the only reason we feel tired - in fact, a lack of sleep is a natural consequence of ageing.

It has been known for decades that we do not sleep as long or as deeply as we age. But why? Researchers say it is linked to the actions of the prefrontal cortex, a region of the brain just behind the forehead that helps to sustain sleep quality but that loses volume with age.

In the latest study, led by Matthew Walker, a professor of psychology and neuroscience at Berkeley, the sleep patterns of a group of 18 healthy 20-somethings and 15 healthy adults in their 70s were compared. As the subjects slept, their brain waves were measured by an electroencephalographic scan.

What emerged was that the older group got about one-quarter of the beneficial slow-wave sleep that typically constitutes 25 per cent of a night's kip than that enjoyed by the youngsters.

Kevin Morgan, a professor of gerontology and director of the clinical sleep research unit at Loughborough University in Britain, says the idea that we are losing sleep because of ageing has scientific merit. Certainly, he says, it is known that the structure of our sleep - specifically, the amount of quality sleep - changes from the age of 40.

As we get older, the phenomenon of polyphasic sleep - getting short bouts across 24 hours as babies do - reintroduces itself, although adults are less responsive to it, meaning that even when they need it, they sleep less.

"There's no single reason sleep patterns alter as we get older," Morgan says, "but a complex shift in hormones, neurotransmitters and other factors later in life can all play a part."

As with other aspects of ageing, genetics are important. "If your gran slept well long into her 80s, then it is likely you have a solid genome. But the menopause and other factors linked to age influence sleep loss. It's a complex relationship."

What concerns experts most are the long-term consequences of sleep loss through ageing. At any age, getting a good night's sleep will have a positive effect on cognitive sharpness.

"We all know that you are more on the ball and less fuzzy-headed when you are not tired," Morgan says. "And it holds true that if you want to hang on to your marbles, you need to get to bed early."

In this latest trial, Walker and his team discovered sleep was directly linked to a rise in forgetfulness and "senior moments". With the prefrontal cortex also known to be critical to consolidating new memories, they discovered a direct correlation between a lack of restorative sleep and memory loss.

"When we are young, we have deep sleep that helps the brain store and retain new facts and information," Walker says. "But as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night."

Slow brain waves generated during deep sleep are what help solidify our short-term memories into longer-term ones, he says.

But could it really be that going to bed early is anti-ageing for the mind?

To test their theory, Walker gave each of his subjects 120 nonsense word pairs to remember, chosen because a key type of memory to decline with age is previously unseen information. A half-hour after being presented with the words, the younger group outperformed the older group by 25 per cent. They then went to bed. In the morning, all subjects were retested while undergoing an MRI. The 20-somethings performed 55 per cent better than their older counterparts.

Even 70-year-olds who had achieved high scores the night before experienced a sharp decline in memory after sleeping.

Others have produced similar results. Last year, a team from the University of Pennsylvania showed that two hours of missed slumber in adults is enough to stop the brain laying down and storing memories.

Simply dropping from eight hours a night to six could result in a sharp drop in work performance.

"What our results really mean for modern life is that sleep is not a luxury," says Ted Abel, the professor of biology who led the study. "It is critically important for the brain."

Not that age-related sleep loss is necessarily a slippery slope down which we are all destined to slide. Encouragingly, there are potential anti-ageing solutions that will reverse the decline.

It is even possible to reverse the effect of ageing and improve quality deep sleep, studies are finding.

One approach being investigated is the enhancement of deep sleep through electrical stimulation. By putting electrodes on the scalps of older people, scientists have found that they can simulate slow waves of deep sleep in the prefrontal area of the brain.

The result? Not just higher energy levels, but a sharper brain and levels of recall. An emerging area of research, it is certainly an approach that may have wider applications.

In the meantime, is there any thing practical we can do to stem our sleep decline? Aerobic exercise - running, walking or swimming - can help, provided it is not done too near to bedtime.

In one study a couple of years ago, troubled sleepers who started exercising for 20-40 minutes four times a week not only found that sleep quality improved but they had more vitality and less drowsiness in the daytime.

Predictably, caffeine can keep you awake - more so as you age. "When you suggest less tea or coffee, people usually say: 'But I've drunk it all my life,' " Morgan says. "What they don't realise is that sensitivity to caffeine increases with age. The amount you are used to suddenly keeps you awake."

Conversely, a cup of coffee after a poor night's sleep could save the day. A few years ago, German researchers at the University of Lubeck gave sleep-deprived volunteers caffeine or a placebo one hour before their memories were tested. Caffeine appeared to have a striking effect as those who consumed it had 10 per cent fewer "false memories".

What might have happened, said researcher Susanne Diekelmann, was that caffeine spurred the prefrontal cortex into action, enabling more accurate recall.

As you get older, Morgan says your daily routine should be "metronomically regulated" if you have trouble sleeping. This is especially important in retirement when a lack of daily structure can throw routine out of kilter. So, if you exercise, do it at the same time of the day. Likewise, a catnap is fine as long as it is planned. Make sure a nap lasts no longer than 45 minutes - drift off for an hour or more and you risk sleep inertia as you progress into a deep sleep.

"Science is drawing our attention to the real value of sleep," Morgan says. "We know that if you sleep poorly, you will function poorly and that age can compound that. We all need to get enough."

THE TIMES