Montreal researchers demonstrate that the need to get enough sleep grows as we age, yet can be more difficult to achieve.

By Brian Bergman

With each New Year that passes we get a little older and, it would seem, a little more tired. The blunt fact is, as we age, our sleep patterns change—usually for the worse. We wake up more often, have more difficulty going back to sleep, and experience less of the deep, dreamless portion of the natural sleep cycle that refreshes the mind and body alike. As we resolve at this time of year to make positive changes in the way we live, is it any wonder that getting a good night’s sleep tops many people’s wish lists?

Julie Carrier, an expert on sleep and aging, is a member of one of Canada’s largest sleep research facilities at the Centre de recherche de l'Hôpital du Sacré-Coeur de Montréal. While it’s long been known that the elderly experience more sleep problems than the young, Carrier’s research has helped establish that changes in sleep patterns begin much earlier in life than previously believed. Moreover, Carrier has discovered that it’s the middle-aged who are at the highest risk of suffering from disruptions in the sleep-wake cycle.

A normal sleep pattern consists of three phases, repeated over roughly 90-minute cycles. The phases are light sleep, slow-wave sleep (otherwise known as deep sleep), and rapid eye movement (REM) sleep—characterized by the eyes moving back and forth beneath the eyelids. While REM sleep is when most dreaming occurs, it’s believed the slow-wave portion is the most rejuvenating part of the sleep cycle. Unfortunately, it’s this phase that steadily deteriorates with age.

As a rule, older people go to bed and wake up earlier than young people, and their sleep is shorter, shallower (less deep sleep), and more fragmented (waking up more often). Once awake, older people have more trouble going back to sleep. They also take longer to recover from sleep deprivation and from disruptions to normal sleep patterns such as shift work and jet lag.

As Carrier completed her post-doctoral sleep research in 1998, she began to ask herself how early in life these changes take place. “For a long time, the middle-aged population was totally forgotten in terms of sleep research,” she says.

She took on a study of 110 men and women between the ages of 20 and 59. Carrier was surprised to learn that the kind of sleep deterioration previously associated only with the elderly actually begins to show up as early as age 30. The most dramatic factor was the loss of slow-wave sleep. Middle-aged subjects had, on average, half the amount of slow-wave sleep as younger subjects.

Carrier’s findings shed new light on the mounting sleep deficit experienced by many people in mid-life. The elderly, she notes, are often able to make up for sleep loss through daytime naps or other alterations in their sleep schedules. The middle-aged, with their multiple social, family, and professional responsibilities, are hard-pressed to do the same.

“One of the first things middle-aged people will cut back on is sleep time,” says Carrier. “This is a very, very bad decision. People should not deprive themselves of sleep.”

It’s long been known that sleep deprivation has a negative impact on mood and alertness. In fact, Carrier notes that the loss of just one night’s sleep can have the same effect on a driver’s reaction times as being over the legal blood alcohol limit. Again, the consequences of sleep deprivation may be hardest on the multi-tasking middle-aged, as it reduces their productivity and puts them at greater risk of accidents.

There is growing evidence that lack of sleep also contributes to a host of health problems, including cardiovascular failure and weakening of immune systems. Moreover, common sleep disorders such as insomnia, sleep apnea, and restless leg syndrome all increase with age.

Carrier’s findings point to the need for more research on the underlying causes and effects of age-related changes in sleep patterns. This, in turn, should lead to better treatment and prevention measures.

In the lab, Carrier uses electroencephalography (EEG) equipment to monitor circadian (24-hour) rhythms such as body temperature. Portable EEG machines allow her to do the same with subjects in their own homes. More recently, she has used functional magnetic resonance imaging to record brain activities of people while they sleep.

“Right now, I can describe the impact of getting older, but I can’t tell you why we lose slow-wave sleep as we age,” says Carrier. “I also can’t say for sure what’s more important—the quality or quantity of sleep we get. Although sleep research has been around for 50 years, there’s still so much we don’t know.”