Even an extra hour's sleep appears to reduce the risk of hardening of the arteries by more than 30 per cent, say University of Chicago researchers who studied the sleeping habits of 500 middle-aged people over five years. Their levels of coronary artery calcification were checked at the start and finish of the study. On average, participants slept for six hours a night, with few getting more than eight hours. Over the five years, 12 per cent developed thickened arteries; those who slept longer were much less likely to do so, WebMD reports.

Fat men are less fertile

Obese men tend to have lower sperm counts - and what they have often aren't much use, say University of Utah researchers, based on a study of 400 men over two years. Those with the highest body-mass indices were three times as likely to have lower sperm counts than men of normal weight, and three times as likely to have low motility, meaning the sperm don't swim ahead, Reuters reports.

Flu's secrets uncovered

US and Japanese researchers have discovered what made the 1918 Spanish flu pandemic so deadly - which may help in combating future outbreaks. The pandemic killed as many as 30 million people. While influenza usually affects the upper respiratory tract, the 1918 flu moved into the lungs, causing pneumonia. By adapting the latest K173 flu virus in tests on ferrets, the team found that the key was three genes that combined to affect a fourth and enabled the 1918 virus to lodge in the lungs, WebMD reports.

Why the cool rule

A US researcher has identified a so-called popularity gene that may make young men more likely to be liked. Previously, Alexandra Burt of Michigan State University found that those with a particular variant of the 5-HT2A serotonin-receptor gene were more popular. Her latest research, based on studies of 200 college students, appears to confirm that their popularity is linked to higher serotonin levels, which in turn are linked to impulsivity, with rule-breaking typically perceived as admirable among young men, WebMD reports.

Cocaine gets them buzzing

Giving bees cocaine sets them dancing and makes them more caring and sharing, say University of Illinois researchers, supporting the theory that hive mentality is based on a reward system hardwired into bees' brains. When foraging bees find high-quality nectar or pollen they appear to get a burst of a neurochemical called octopamine and perform a so-called round or waggle dance back in the hive to show others where to go. Cocaine affects the flow of octopamine, with the result that the bees are more likely to dance regardless of the quality of or need for food, healthday.com reports.