Short Sleepers May Catch More Colds

Want to avoid catching a cold this winter? Start by getting more than six hours of sleep a night.

In what may be the first study of this kind, researchers say they found that adults who sleep less than five or six hours a night are four times more likely to catch a cold than than those who get at least seven or more hours of sleep.

“Sleep plays a role in regulating the immune system, and that’s how we think it influences susceptibility to the common cold,” said Aric A. Prather, an assistant professor of psychiatry at the University of California, San Francisco, who is the lead author of the study, published this week in the journal Sleep.

Previous research had suggested a link between less sleep and higher vulnerability to colds, but that study relied on subjects self-reporting the number of hours they slept. The new study was the first to measure actual sleep. To do so, the researchers used a technique called wrist actigraphy, which uses a watchlike device with an accelerometer that measures movement and inactivity and which, when combined with sleep diaries, provides a more accurate accounting of sleep.

“This study reinforces the notion that sleep is just as important to your health as diet and exercise,” said Dr. Nathaniel F. Watson, president of the American Academy of Sleep Medicine. “People need to view sleep as a tool to achieve a healthy life, rather than as something that interferes with all their other activities.”

Many Americans don’t get enough sleep; a 2013 survey by the National Sleep Foundation said that one in five adults gets less than six hours of sleep on an average work night.

Poor sleep has been linked to numerous chronic illnesses, and new guidelines issued this year by the American Academy of Sleep Medicine and the Sleep Research Society urge adults to get seven or more hours of sleep per night on a regular basis to promote optimal health.

The guidelines say that sleeping less than seven hours per night is associated with weight gain, diabetes, hypertension, heart disease and stroke, depression and premature death, as well as “impaired immune function, increased pain, impaired performance, increased errors and greater risk of accidents.”

The new study recruited 164 men and women aged 18 to 55 from the Pittsburgh area between 2007 and 2011, and put them through extensive health screenings, questionnaires and interviews to determine their levels of stress, their general temperament and their use of alcohol and tobacco. Then the researchers measured the subjects’ normal sleep habits for a week, before sequestering them in a hotel and deliberately administering them nasal drops containing the cold virus.

The volunteers were monitored for a week and daily mucus samples were collected to see if they had become infected.

Those who slept less than six hours a night the week before the exposure were 4.2 times more likely to catch the cold compared with those who got more than seven hours of sleep, researchers found. Those who slept less than five hours a night were 4.5 times more likely to catch the cold. (Those who slept just over six hours but less than seven weren’t at increased risk.)

It didn’t seem to matter whether the sleep was continuous or fragmented, Dr. Prather said. The results were adjusted to control for differences among subjects, including pre-existing antibody levels to the rhinovirus, age, sex, race, body mass index, the time of year when the trial was done, education, income, health habits such as smoking and physical activity, and psychological variables such as stress.

“The good thing about this is that there are opportunities for people to improve their sleep, and most people admit they need more and want more,” Dr. Prather said, adding, “it’s just about looking at the barriers and making it a priority.

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Why Do Muscles Ache a Day or Two After Exercise?

After rigorous exercise, the muscle pain is more acute a day or two later rather than immediately. Why is that?

Welcome to the equivocal effects of delayed onset muscle soreness, the scientific term for aches that accumulate and intensify a day or two after a strenuous workout. Usually, D.O.M.S. involves not just pain but also “loss of strength and range of motion in the affected area,” said Scott Sailor, a professor of kinesiology at Fresno State University in Fresno, Calif., and the president of the National Athletic Trainers’ Association.

D.O.M.S. commonly occurs after exercise that involves lengthening muscles while they contract, Dr. Sailor said, such as running downhill. But it can develop after any exertion that is more intense or prolonged than is normal for you.

Such strenuous workouts can cause multiple slight tears to the muscle tissue, after which a variety of cells and substances migrate to these muscles to help them start healing.

Interestingly, these substances are not necessarily the same as those that arrive after a more severe muscle injury. Molecules that promote inflammation and swelling, for instance, tend to predominate in tissues affected by a serious injury, but can be absent in tissue affected by D.O.M.S., recent studies show.

Similarly, “there was a time when we attributed the muscle soreness to lactic acid,” Dr. Sailor said. “We have now learned that lactic acid leaves the muscle so quickly” that it cannot be involved in causing D.O.M.S.

In essence, researchers remain puzzled about what cellular reactions cause D.O.M.S.

Likewise, there is controversy about how best to treat it.

“Various treatments have been attempted over the years,” said Dr. Sailor, including massage, icing and anti-inflammatory painkillers. “At best, they have decreased the perception of pain,” he said, but only temporarily. No treatment yet has been shown to actually reduce the length of time that muscles remain sore and weak.

So if you do develop D.O.M.S., accept that, for the next five to seven days, you are going to be sore. Refrain from strenuous exercise during this time, Dr. Sailor said, although gentle walking is fine.

And, if it is any consolation, your muscles should be stronger after they recover.

In your future workouts, Dr. Sailor said, increasing the duration or intensity gradually should increase strength and fitness to limit the potential of experiencing the effects of D.O.M.S.

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Filtered Sunlight Is Good Cure for Infant Jaundice, Study Says

Filtered sunlight is a cheap, effective way to treat infant jaundice, according to a study by Stanford researchers.

Jaundice — caused by an excess of bilirubin in the blood — leads to brain damage or death in about 150,000 babies a year in poor countries. The problem is common in newborns, whose livers sometimes need several days after birth to generate the enzymes needed to break down bilirubin, which is released when red blood cells break down. Yellow skin and eyeballs are common symptoms.

In wealthy countries, jaundiced newborns are placed for several days under sunlamps that emit extra blue wavelengths of light and minimal ultraviolet or infrared ones.

It was established during World War II that artificial sunlight cures jaundice, which more than 28,000 soldiers developed after getting yellow fever vaccine made from human blood.

For years, American research focused on drugs to block bilirubin formation, while hospitals relied on lamps and, in extreme cases, transfusions to treat patients.

But hospitals in poor countries may be unable to afford lamps or may lack a steady electricity supply to run them.

The Stanford team, whose work was published last month in The New England Journal of Medicine, tested whether real sunlight —which is plentiful at many hospitals in tropical climes — could be made safe enough for babies to lie in for hours a day.

They treated 433 babies for jaundice at a hospital in Lagos, Nigeria. Half received sunlamp phototherapy, and half slept in outdoor cribs or their mothers’ laps under canopies of plastic film that filtered out ultraviolet and infrared rays.

The sunlight treatment was slightly more effective, and the children did not have more sunburn, dehydration or overheating.

The researchers have designed a small greenhouse to be used in windier or colder climates.

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Spread of Cigarettes in China

Chinese men now smoke one-third of all the world’s cigarettes, and a third of all young men in China are doomed to eventually die from the habit, scientists in China and Britain have concluded.

Their study, published last week in The Lancet, estimated that two-thirds of all males in China smoked, more were still taking up the habit and more were starting as teenagers, which adds risk.

With population growth stagnant, the number of men 60 or older is expected to double by 2030, and the number dying of smoking-related ailments each year will triple, hitting three million a year by 2050.

More smokers are stopping by choice, the study found, but still only 9 percent did so.

By contrast, smoking rates among women in China have dropped sharply; about 10 percent of older women smoke, but only about 1 percent of middle-aged women do. However, another recent study detected rapid increases among teenage girls in some regions.

Before China achieved prosperity, the Lancet study said, smokers typically started at age 25, more smoked pipes and many could not afford multiple cigarettes every day.

The study estimated future smoking-related deaths from many causes, including lung cancer, obstructive pulmonary disease, stroke, heart failure and other cancers. Lung disease rates are already high in China, even among nonsmokers, owing to urban air pollution and to indoor wood fires used by the rural poor.

The study was led by scientists from China’s Center for Disease Control and Prevention, the Chinese Academy of Medical Sciences and the University of Oxford.

Antismoking efforts in China face a difficult political situation: The central government has a monopoly through the Chinese National Tobacco Corporation, and more than 7 percent of government revenue comes from it.

According to an editorial accompanying the study, myths about smoking persist in China: that Asians are less susceptible to its dangers, that it is an ancient Chinese tradition and that quitting is easy.

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To Prevent Malaria in Humans, Scientists Try Protecting Pigs

For years , scientists have known of a sneaky way to kill mosquitoes: Give humans a deworming pill.

The active ingredient, ivermectin, kills not only worms infesting people but also mosquitoes who drink their drug-laden blood. (Ivermectin also kills lice, bedbugs and other blood-feeders. The drug’s inventors recently received a Nobel Prize in Physiology or Medicine.)

Turning everyone in a village into a walking mosquito bomb, many scientists agree, could stop or slow transmission of malaria, yellow fever, dengue, chikungunya and other diseases.

But villagers with worms normally receive only one or two pills a year. Researchers aren’t certain it is possible — or safe — to boost blood levels of ivermectin high enough to wipe out generations of mosquitoes during the biting season, which can last for months.

Scientists at the medical school of the University of Barcelona have come up with a novel alternative: Use livestock.

In a poster presentation at a meeting of the American Society of Tropical Medicine and Hygiene in Philadelphia last week, the researchers showed how they had implanted two-inch soft silicone rods releasing a steady dose of ivermectin under the skin of pigs.

Many poor farmers keep their animals near or even inside their homes to protect them from predators or thieves.

Some disease-carrying mosquito species alternate between biting animals and humans, said Dr. Carlos Chaccour, a researcher at the University of Barcelona’s Institute for Global Health and the University of Navarra. Ivermectin will kill most mosquitoes, but the dose needed varies by species.

Because not all poor farmers raise pigs — Muslims, for example, do not — the method will still need to be tested in cattle, goats, camels and other livestock.

Animals usually tolerate high doses of ivermectin safely, Dr. Chaccour said, but must be drug-free for some time before they are safe to eat. For example, cattle should not be slaughtered for food until 90 days after a single deworming treatment, according to guidelines by the United Nations Food and Agriculture Organization.

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