WASHINGTON — More people pull the night shift. Teens text past midnight and stumble to class at dawn. Travelers pack red-eye flights.
Nodding off behind the wheel isn't the only threat from a lack of shut-eye. There's growing evidence that people who regularly sleep too little and at the wrong time suffer long-lasting consequences that a nap won't cure: An increased risk of diabetes, heart disease and other health problems.
"We have a societal conspiracy for sleep deprivation," says Russell Sanna of Harvard Medical School's sleep medicine division, who attended a TEDMED conference last week where scientists called sleep loss one of health care's big challenges.
Just how unhealthy is it? Consider how sleep may play a role in the nation's diabetes epidemic.
Studies have long shown that people who sleep fewer than five hours a night have an increased risk of developing Type 2 diabetes, the kind that tends to strike later in life.
Rotating shift work — three or more night shifts a month interspersed with day or evening hours — raises the risk, too, says a recent report from researchers who analyzed years of medical records from the huge Nurses' Health Study.
Diet and physical activity are big factors in Type 2 diabetes. Certainly it's harder to work out or choose an apple over a doughnut when you're tired, especially at 3 a.m. when your body's internal clock knows you should be sleeping.
But a study published last week shows sleep plays a more complex role than that. As sleep drops and normal biological rhythms are disrupted, your body physically changes in ways that can help set the stage for diabetes, reports neuroscientist Orfeu Buxton of Boston's Brigham and Women's Hospital.
Buxton's team had 21 healthy volunteers spend almost six weeks living in a laboratory where their diet, physical activity, sleep and even the light was strictly controlled.
The volunteers started out well-rested. But for three of those weeks, they were allowed only about 5 1/2 hours of sleep every 24 hours — at varying times of the day or night, to mimic a bad shift rotation or prolonged jet lag.
That knocked out of whack the body's "circadian rhythm," a master biological clock that regulates such patterns as when we become sleepy and how body temperature rises and falls.
What happened was startling: Blood sugar levels increased after meals, sometimes to pre-diabetic levels, because the pancreas stopped secreting enough insulin, Buxton reported in the journal Science Translational Medicine.
At the same time, the volunteers' metabolic rate slowed by 8 percent. The researchers had them on a diet so they didn't gain weight — but Buxton says typically, a metabolism drop of that size could mean gaining 10 to 12 pounds over a year.
The consumer message:
The National Institutes of Health says adults need between seven and nine hours of sleep daily for good health.
If you work nights, go straight to bed when you get home, Buxton advises. Avoid too much light along the way. Thorpy says wearing yellow- or orange-tinted sunglasses on the drive home can block short-wavelength "blue light" that triggers wakefulness.
Let natural light help keep your biological sleep clock on schedule, advises Harvard's sleep-education Web site.
For most people, sunlight in the morning is key. For the night shift, more bright light in the evening shifts people's internal clock, Buxton explains.
For anyone, a sleep-inducing bedroom is one that's dark, quiet and cool. Avoid caffeine, alcohol and stressful situations near bedtime. Electronics right before bed aren't advised, either. Going to bed and waking up at the same time every day also helps.
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