Sleep, through the ages


Smart sleep: A 90-minute nap equals a night’s rest.

The answer is sleep, according to several studies presented at the annual meeting of the American Association for the Advancement of Science on Sunday.

A study conducted by researchers at the University of California San Diego (UCSD) found that 68-year-old adults, on average, did better on a simple memory test if they got more sleep.

In younger adults, aged 27 on average, the quality of sleep also affected how they performed on the same test.

“What mattered in the younger adults was sleep efficiency—that the sleep was consolidated into one solid chunk," says Sean Drummond, a professor at UCSD’s department of psychiatry who led the study, adding that sleeping soundly and uninterruptedly happens less and less frequently with age. “The most common change in sleep as we age is (that) you wake up in the middle of the night and you’re awake for some time, meaning you have lower sleep efficiency," Drummond says. “In the older adults what we found is that waking up in the middle of the night did not affect brain function or performance the next day but if a young adult did that, it had significant detrimental effects on brain function," he says.

Another study looked at the possible benefits of napping. “Our question first was, could you get the same benefits from a short daytime nap as a full night of sleep," says Sara Mednick, also from UCSD’s department of psychiatry. “We started looking over a number of different tests, beginning with a visual learning test, which showed that if you had a 90-minute nap, you showed the same level of benefit as a full night of sleep," Mednick says. “There’s something very special about naps," she says. Not everyone has the luxury of being able to catch a few Zs in the middle of the day, and as a substitute, many seek a caffeine boost. But a double espresso doesn’t work as well as a 20-minute nap, says Mednick.

“On some tasks, such as those involving perceptual memory, caffeine works as well as a nap," says Mednick. “But when the task involves the hippocampus, the area of the brain devoted to explicit memories you can manipulate consciously, such as learning a list of words or a phone number or name, with caffeine your memory for those kinds of tasks is decreased," she says.

Meanwhile, another study found that “two significant clinical and public health problems, sleep disorders and drug use in teens" are closely intertwined. Not only are teens who sleep less than 7 hours a day more likely to do drugs, but they are also likely to pass both their bad sleep and drug-use behaviour to friends and siblings. “An adolescent who does not get enough sleep can influence a friend’s sleep behaviour, which increases the risk that the friend will use drugs," the study says. Researchers at UCSD and Harvard University found that teens with a friend who sleeps less than 7 hours a night are 11% more likely to sleep less than 7 hours themselves and 19% more likely to use marijuana than teens whose friends get a good night’s sleep. The study was the first to find that poor sleep habits and drug use spread through teenagers’ social networks “like a contagion", extending to up to four degrees of separation—or to friends of friends of friends of friends.

The US National Sleep Foundation recommends that teens get at least eight-and-a-half hours of sleep and that adults, both younger and older, get at least 7 hours.


Regulate: Binge drinking isn’t good for your heart.

Occasional binges undo alcohol’s benefits

— Reuters

While research has linked moderate drinking to better heart health, a new study suggests that those benefits disappear when drinkers add the occasional binge to the mix. Pooling data from 14 previous studies of moderate drinkers, researchers found that those who drank heavily ever so often were 45% more likely to develop coronary heart disease—where plaque build-up in the heart arteries impedes the flow of blood and oxygen. The study was reported in the American Journal of Epidemiology earlier this month.


Most test-tube babies doing far

— AP

More than 30 years after the world greeted its first “test-tube" baby with a mixture of awe, elation and concern, researchers say they are finding only a few medical differences between these children and those conceived in the traditional way.

Around three million children have been born worldwide as a result of what is called assisted reproductive technology, and injecting sperm into the egg outside the human body now accounts for around 4% of live births, researchers reported at the annual meeting of the American Association for the Advancement of Science on Sunday. The majority of assisted reproduction children are healthy and normal, according to researchers, though some of these children do face an increased risk of birth defects, such as neural tube defects, and low birth weight, which is associated with obesity, hypertension and type 2 diabetes later in life. “Overall, these children do well," says Andre Van Steirteghem of the Brussels Free University Center for Reproductive Medicine in Belgium. “It is a reassuring message, but we must continue to follow up."

Carmen Sapienza, a geneticist at Temple University School of Medicine in Philadelphia, US, noted that few of these test-tube children are older than 30, so it’s not known if they will be obese or have hypertension or other health problems at age 50 or older. Sapienza adds that researchers found differences in 5-10% chromosomes between assisted reproduction children and other kids. What’s not clear is whether these differences result in some way from assisted reproduction techniques or if they stem from other factors, perhaps ones that caused the couple’s infertility in the first place. “However, because some of the genes found to be affected are involved in the development of fat tissue and the metabolism of glucose, it will be interesting to monitor these children long term to determine whether they have higher rates of obesity or diabetes," says Sapienza.

“There are genetic causes of infertility that you can bypass now," Van Steirteghem says. “But this may mean that the next generation will be infertile, and that is something that all clinics should mention."