New research pinpointing the link between the body clock and metabolism may pave the way for scientists to treat an array of health problems, ranging from diabetes to sleep disorders.

In humans and other mammals, circadian rhythms, or the body clock, control everything from sleep to hormones. It is present – albeit less sophisticated – in life forms all the way down to plants and yeasts to ensure that important functions, such as cell regeneration, occur at the optimal time of the 24-hour day-night cycle. (It's also to blame for jet lag.) Scientists have long suspected that it is connected with metabolism (the way our bodies use energy), but they weren't sure exactly how.

In an attempt to unlock this molecular mystery, Joe Bass, an assistant professor of neurobiology and physiology at Northwestern University in Evanston, Ill., and colleagues wanted to see how the two functions might be related in mammals. They placed the mice – some with normal circadian rhythms and others whose rhythms had been disrupted – in complete darkness for 48 hours (in an effort to confuse normal body cycles). Their findings, published today in an online edition of Science: levels of the enzyme Nicotinamide adenine dinucleotide (NAD+), known to play a key role in metabolism, were low and constant in the mice with disrupted clocks but, even in perpetual darkness, levels of the enzyme in unaltered animals fluctuated in tune with daily cycles.

People who get less than seven hours of shut-eye nightly are three times more likely to catch a cold than those who get eight or more hours, according to a new study. Researchers speculate that a lack of sleep may compromise immune function, making people more vulnerable to the common cold. 

"The really striking thing about this study for us is how little differences in sleep can have a big impact on your susceptibility," says Sheldon Cohen, a psychoneuroimmunologist at Carnegie Mellon University in Pittsburgh, Pa., and lead author of the study published today in the Archives of Internal Medicine. 

Previous research has shown that sleep deprivation may trigger changes in the immune system that could make a person more vulnerable to infection. For example, poor sleep may lead to a dip in the number of killer T-cells, which destroy viruses and bacteria, as well as to lower levels of interleukin-2, a protein that stimulates production and growth of many infection-fighting cells, including T-cells. But this is one of the first studies that links sleep deficits to increased susceptibility to the rhinovirus, the most common culprit behind, well, the common cold.

A bizarre disorder that causes people to physically act out their dreams while sleeping is associated with a dramatically increased risk of developing dementia, and Alzheimer's and Parkinson's diseases, according to new research that suggests the sleep disorder may actually be an early symptom of those conditions.

People with REM sleep behavior disorder, a condition caused by the brain's failure to immobilize a person's muscles while they're dreaming, have an estimated 52 percent risk of developing one of those neurological diseases within a dozen years, according to a study published in today's Neurology. Among people without REM sleep behavior disorder, that risk is about 5 percent, according to study author Ron Postuma, an associate researcher in neurology at the Sleep Disorders Center at Sacre-Coeur Hospital in Montreal.

Ah, sleep. You hardly need a doctor to tell you that getting too little of it can make you irritable and lethargic. Now it looks like how many zzz's you get may affect whether fatty plaque deposits build up in your arteries — a precursor to heart attacks and angina, or chest pain.

University of Chicago docs recorded how much sleep 495 middle-aged folks got over three nights using a monitor worn on their wrists, and examined their hearts for coronary artery calcification using computed tomography (CT) scans. Then the scientists checked back in with them five years later, conducting the same tests.

Sleep apnea, a disorder that can cause sufferers to temporarily stop breathing while snoozing, has long been associated with obesity. Paradoxical new findings suggest an ironic benefit: the worse the disease gets, the more calories patients burn.

"It's something of a silver lining," says Eric Kezirian, director of the division of sleep surgery at the University of California, San Francisco, whose research appears in today's Archives of Otolaryngology-Head & Neck Surgery. "It's not hurting in certain areas, but may be hurting in other areas."

Could more sleep be on the horizon for fatigued medical residents? If not, it should be, says the Institute of Medicine (IOM), which in a report released today recommends shorter shifts and scheduled time for snoozing.

The IOM doesn’t suggest that the docs in training work less than the maximum 80-hour weeks set five years ago by the Accreditation Council for Graduate Medical Education (ACGME), which accredits residency programs. But it says residents shouldn’t be allowed to work for more than 16 hours straight without an uninterrupted sleeping break that's at least five hours long.

The ACGME rules allow residents to work as long as 30 hours without a break, but "adequate time for rest and personal activities must be provided" after that in the form of 10 free hours. Some 43 percent of residents surveyed, however, said they routinely worked longer than the maximum amount.

You might be wondering what science has to do with Thanksgiving. Its only complexity should involve family feuds and kitchen disasters, right? Have we got news for you: there are myths to be shattered about this most American of holidays, including the alleged soporific effects of turkey and the assumption that gratitude has nothing to do with good health.

Our in-depth report on the science of Thanksgiving tackles those and other questions you may be mulling as you prep Tom in your oven. Don’t you want to know what makes the meat on your plate white or dark? The reason is all in the family – the family of turkey genetics, that is. And can you eat turkey without becoming drowsy? We’ve got the answer.