More people pull the night shift. Teens text past midnight and stumble to school at sunrise. Travellers 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 healthcare's big challenges.
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, according to a recent report from researchers who analysed 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 exercise or choose an apple over a doughnut when you're tired, especially at 3am when your body's internal clock knows you should be sleeping.
But a recently published study showed sleep plays a more complex role than that. As sleep drops and normal biological rhythms are disrupted, the 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 ½ 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 eight per cent. 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 about 5kg pounds over a year.
The results make sense, says Dr Michael Thorpy, sleep centre director at New York's Montefiore Medical Center and a neurology professor at Albert Einstein College of Medicine.
"If we're going to spend a third of our day sleeping, there's got to be a good reason for it," said Dr Thorpy.
Impaired sleep has been linked to high blood pressure, heart disease, obesity, depression, memory impairment and a weakened immune system. Plus, The World Health Organization has classified night shift work as a probable carcinogen, because too much light at night may hamper a hormone involved both with sleep and suppressing tumour cells.
Don't people adjust to the night shift if they're on it long enough? Buxton said rotating shifts could be the biggest worry.In his study, the volunteers' bodies went back to normal after nine nights of sufficient sleep at the right time. No one knows how long it takes before sleep deprivation and an off-kilter biological clock may cause permanent damage.
Dr Thorpy said natural night owls seem to adapt better to night shifts, but people never fully adapt if they swing back to daytime schedules on their days off. About 30 per cent of regular night workers have trouble sleeping during their off hours or are particularly fatigued, he said, something termed "shift work disorder."
For good health:
* The National Institutes of Health in the US 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. Avoid too much light along the way. Dr 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 website. 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.
* 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.
Read more here
No comments:
Post a Comment