The American Sleep Disorders Association recommends American adults get seven or more hours of sleep each night.  Many don’t.  Between work, children, cellphones, aging parents, more work, illness and overall stress, lots of folks get a whole lot less sleep than they want. They need sleep recovery.

So they sleep in over the weekends, or whatever days they don’t have work or school.  Does it help?  How much?

The question of sleep recovery divides the sleep research community; many think it does not really work.  Yet a recent Swedish study gives a basis for some hope.

Sleeping Too Little or Too Much?

It’s long been known that mortality and sleep follows a U shaped curve.  If you sleep too little, you die earlier than expected.  If you sleep too much, you die earlier.

Epidemiologists have long known there’s a good reason for longer sleep’s association with morality: llness.  People who are sick tend to sleep long, then longer.  The body does not regenerate properly with many acute and chronic illnesses.   It needs more time for recovery.

Thus when ill we sleep more.

The short sleep part of the equation seems a bit more volitional.  People can cut their sleep time for work and social reasons.  Mostly they try to recover over the weekends.  Korean secondary students, for example, have high school, prep school, and homework until late at night.  Some studies show they average five hours sleep on the weekday and a whopping 13 hours on the weekend.

Does it work?

From the standpoint of performance, the data suggest not.  In the last decade  the concept of “social jet lag” has advanced.  People may recover the total hours of sleep they feel they need to work well, but there is a price to pay.  Overall performance declines. Heart attacks and heart disease increase with weekend “sleeping in.”  The peak time of death in the U.S. remains Monday morning.  The reason is biological clocks.  Humans did not evolve with weekends.  Change your time of waking and sleeping, as shift workers do, and a long list of health and performance consequences ensues.

But what about survival?  Here we can look to Sweden.

Mortal Weekends?

Torbjorn Akerstedt has been doing excellent sleep research for a long time.  One of his memorable studies of train conductors found that many of were falling asleep on their night shifts, but did not look asleep.  Their glassy eyes stayed wide open though their brain physiology demonstrated slumber, something to think about when you hail a late night taxi.  Akerstedt was also able to show the progression of “Exhaustion Syndrome,” which Americans call chronic fatigue, and how it disproportionately affected middle aged women in professions like teaching and nursing who found their home and work burdens rising.

In a recent study Akerstedt’s group followed almost 44,000 people for 13 years, asking them about their sleep..  For men and women under 65, sleeping less than 5 hours markedly increased mortality, on the order of 50%.  But in the group that slept in over the weekends, the mortality increase did not occur.

At least for them, sleeping in  on the weekends provoked less mortality.  The effect disappeared for those over 65.

There were many problems with this study, which did not control for all the variables most researchers are interested in.  But it did highlight something many believe – when you don’t get enough sleep, try to get more.

Sleep is Like Food

Many sleep researchers think sleep recovery, getting effective sleep regeneration after you’ve been sleep deprived, never fully occurs.  Matthew Walker at Berkeley is  one who feels sleep debt can rarely, if ever, be fully paid back.  The body can’t survive without sleep. It can’t rebuild  properly without it, and what’s lost is lost.

Akerstedt’s paper argues that even if performance may be diminished, survival may be served by recovery sleep, even if biological clocks are disrupted as a result.

One way to think of this is to view sleep like food.  When people are starved, they need nutrition.  They’ll get it any way they can.  Indeed, people who voluntarily give up sleep involuntarily nap, often in inappropriate places, including the frequent microscleeps that occur on the highways.

And people who are starved, once given food, do recover many functions.  Yet the long consequences are often unconsidered.  The Dutch famine of 1944 led to many deaths decades later.  Food deprive infants or children and the behavioral and physiologic results extend the rest of their lives.

And just as there are foods that lead to better health outcomes, there are differences in sleep patterns that lead to better performance and health. The snickers bar may be deeply alluring, but is ultimately no match for the multicolored, unprocessed salad.

It’s not all about taste.  It’s about what you need.

So it is with sleep.  Think of sleep as like food.  Sometimes avoiding it looks wondrously attractive, especially when a funny video, a gossipy text, or the prospect of an exciting white night awaits.

But something will give.  And you’ll need it back.  And there is just so much time in one’s life.