Scientists are increasingly finding that sleep is a critical component of good health. Lack of shuteye has been linked to obesity, heart disease, and diabetes in a variety of studies.
And now new research shows that the less older people sleep, the faster their brains age—which can lead to cognitive decline and dementia.
Researchers analyzed the sleep habits of 66 older Chinese adults, and then measured the size of their brain ventricles (a marker for cognitive decline and development of neurodegenerative diseases such as Alzheimer’s). The researchers found that the study participants who slept the least had the largest decrease in brain volume and function.1
According to this research—as well as other studies—seven hours of sleep a day seems to be the “sweet spot” for maintaining optimal brain health.
Of course, we all know this is easier said than done. You probably remember how you were able to sleep all through the night (and sometimes late into the morning) during your teens and 20s. But by age 40, it is increasingly common to wake several times during the night. And the older we get, the lighter our sleep becomes. Waking frequently during the night becomes a fact of life.
But surprisingly, a new study shows this may not necessarily be harmful in the long run. It all comes down to what scientists call “sleep efficiency.” Basically, this is the time you spend actually sleeping versus the time you spend tossing and turning in bed.
For years, experts believed sleep efficiency declined with age. But this new research shows it actually increases in your 60s and 70s.2 Read on and I’ll tell you how.
Why some of your most important sleep may not happen at night
The new research is based on data from the NHK Japanese Time Use Survey, which has been carried out since 1960. Of course, the average lifespan in Japan is the longest in the world, so that provides plenty of data regarding how sleep patterns change with aging.
The survey found that as people get older, the amount of time they dedicate to sleeping steadily increases. Why? Because unlike other sleep data, this survey counts all slumber during a 24-hour period, rather than just nighttime snoozing.
That means naps are considered valid—and valuable—sleep time.
The study author used survey data to calculate how much time different age groups spend actually sleeping versus trying to sleep. He found that both sleep efficiency and sleep time are highest in a person’s teens, then steadily decline through their 20s and 30s. By the time they reach their 40s and 50s, people actually have both the lowest average sleep time and the lowest sleep efficiency.
But according to this study, once people reach their 60s and 70s, both sleep time and sleep efficiency increase again. The study author attributed this growth, in part, to napping.
Indeed, napping often becomes more common as we age. In fact, it may be what nature actually intends us to do.
Don’t refuse an afternoon snooze
One change that accompanies older age is the tendency to go to bed earlier and wake up earlier. Accordingly, taking daytime naps should also become more common.
Both science and tradition show that coordinating our sleep schedules with the daily pattern of the sun is healthy. In Poor Richard’s Almanac, Benjamin Franklin famously said, “Early to bed and early to rise, makes a man healthy, wealthy and wise.”
But there is also a natural cycle during the day of wakefulness and sleepiness, which is recognized in the practice of traditional Indian Ayurvedic medicine, for example.
Drowsiness sets in after the noontime meal and again after the sun begins to decline in the sky. In school and at work we learn to fight off this natural sleep cycle. But as we retire or cut back on work, we have more control over our daily lives and schedule—meaning we can lie down for an afternoon nap if so inclined.
Other cultures have learned to accommodate this natural cycle by taking time off after the noon meal for the traditional siesta. When I was young, restaurants, shops, museums, and workplaces throughout southern Europe would shut down for several hours after lunchtime. While this practice has recently fallen out of favor in some places, it was still common well into the 1990s. (I can personally vouch for the fact that as recently as 1996 in Aix-en-Provence, France, one could have starved in the street just as soon as find a restaurant that was actually open during mid-afternoon.)
Of course, napping has never been a common practice for American adults. But perhaps it should be. After all, while some computerized “brain training” approaches may provide cognitive benefits (see page X this issue), it seems like the best results may come from shutting down the computer and getting some shuteye.
So this time of year, when it is cold and dark outside anyway, don’t hesitate to get in that long winter’s nap.
1Lo JC, et al. “Sleep Duration and Age-Related Changes in Brain Structure and Cognitive Performance. “Sleep 2014; 37(7): 1,171-1,178
2Uchida S. “Does sleep really shorten when we get older?” Sleep and Biological Rhythms 2014; 12(4): 308-309