What the scientists are saying…

Screen time “good” for teens Parents worry about their children being glued to screens for hours a day – but now scientists have found evidence that in moderation, it can be good for teenagers’ emotional well-being. Researchers from Oxford University’s Internet Institute analysed self-reported data from 120,000 15-year-olds across the UK, and found that using smartphones and computers, and playing video games, was associated with higher levels of well-being – at least, up to a point. With computers, well-being “peaked” at four hours and 17 minutes a day on weekdays, before starting to dip again; when it came to watching TV, this “Goldilocks” moment (not too much, not too little) came at three hours and 41 minutes; for video games, it was one hour and 40 minutes; while for smartphone use, it was one hour and 57 minutes. When it came to weekend use, even longer periods were associated with increased well-being. “Our research suggests that some connectivity is probably better than none, and there are moderate levels that as in the story of Goldilocks are ‘just right’,” said lead author Dr Andrew Przybylski. However, the study didn’t consider the implications for other aspects of teenage development; nor did it calculate the cumulative effect of using multiple devices.

Restrict calories, live longer Can people live a lot longer by eating a lot less? Many studies of lesser organisms, from yeast through to worms and mice, have found calorie restriction significantly increases lifespan, says the New Scientist. And as a result, it’s been proposed that humans should try cutting their kilocalories to between 1,500 and 1,800 a day. (The recommended intake is about 2,000 for women, and 2,500 for men.) Some people already do this, and it appears to confer health benefits. But it has been unclear if calorie restriction extends the lifespan of long-living mammals. Now, two studies of macaque monkeys, which usually have a life expectancy of about 26 years in captivity, have shed light on this question. Both of the studies, which began in the late 1980s, are ongoing, and one has been hampered by the control group eating fewer calories than expected. However, initial analysis suggests the monkeys on a diet are indeed living between two and six years longer than their counterparts. That is equivalent to around a decade in humans – but it’s not as impressive as the difference in mice: they lived 50% longer.

Asthma-free asthmatics Millions of people taking medicines for asthma may not actually have the condition, reports The Daily Telegraph. Researchers in Canada conducted a series of tests on some 600 adult volunteers who’d been diagnosed with asthma within the last five years, to ascertain their lung function – and found that a third didn’t seem to have the condition. About two-thirds of the people in this group had minor conditions such as heartburn; a handful had undiagnosed cardiovascular problems; the rest seemed to be healthy. The researchers then gradually reduced the apparently asthma-free patients’ medicines, with almost no ill-effects. It was impossible to tell, the researchers said, how many of those in this group had been misdiagnosed with asthma, and how many had simply recovered from it (only a third of them had been taking medicines daily). But either way, the implication is that many patients without asthma are taking asthma drugs. The research tallies with a recent Dutch study, which found that more than half of children diagnosed with asthma didn’t have it. Last year, NHS doctors were urged to use tests to diagnose the condition rather than relying on self-reported symptoms.

Vampire bats drink human blood Despite their alarming name, vampire bats’ bodies aren’t adapted to process mammalian blood: birds make up their diet. But when a team of scientists in Brazil examined 70 samples of bat faeces, three of the 15 they managed to get DNA from had traces of human blood. This was a surprise because in previous studies, the bats shunned pigs’ blood even when deprived of other food. The team suggests they are changing their diets because of human encroachment into their habitats. This is a worry, as bats can carry a virus – hantavirus – that can be fatal to humans.