Which high school sports cause kids the most injuries? Plus, what to do about sleeplessness, and more health news

Fewer high school athletes are getting hurt playing sports, but those who do are more likely to suffer severe injuries that require surgery or a timeout from their chosen sport, new research shows.

Which teens are most at risk? Those who participate in football, girls’ soccer and boys’ wrestling, the study authors found. Knee and ankle sprains and strains, along with head injuries such as concussions, were the most common injuries seen.

Exactly why injuries are becoming more severe isn’t fully understood, but having kids specialize in sports too early may play a role. That can lead to an increase in overuse injuries, overtraining and burnout, said study co-author Jordan Pizzarro, a medical student at George Washington University School of Medicine and Health Sciences, in Washington, D.C.

Still, the new data isn’t a reason for kids to stop playing sports.

Can vitamin D lower dementia risk?

Quite possibly, a team of British and Canadian researchers report.

In their study, investigators spent roughly a decade tracking more than 12,000 older people. None had dementia at the start of the study period. In the end, the team determined that those who had been taking vitamin D supplements during that time appeared to face a 40% lower risk for dementia, compared with those who had never taken the supplements.

Even so, Claire Sexton, senior director of scientific programs and outreach at the Alzheimer’s Association, cautioned that much more research is needed to better understand a possible link between vitamin D and dementia risk.

A new study is enough to take your breath way: Nearly no place on Earth is free of air pollution, it found.

The study “provides a deep understanding of the current state of outdoor air pollution and its impacts on human health. With this information, policymakers, public health officials and researchers can better assess the short-term and long-term health effects of air pollution and develop air pollution mitigation strategies,” said study co-author Yuming Guo, from the Monash University School of Public Health and Preventive Medicine in Melbourne, Australia. He spoke in a university news release.

The researchers found that only 0.001% of the global population is exposed to World Health Organization-established safe levels of ambient fine particulate matter known as PM2.5.

Only 0.18% of the global land area had safe levels of pollution, the study found.

New research offers up some good news for diehard marathon runners: You don’t necessarily have to give up running if you are experiencing hip or knee pain.

Contrary to widespread opinion, running marathons does not increase your risk for developing hip or knee osteoarthritis, the wear and tear form of the disease, a new study of seasoned Chicago marathoners showed.

“You don’t develop knee or hip osteoarthritis simply because of how fast you run or how many miles you put on your body,” said study author Dr. Matthew James Hartwell, an orthopedic surgery sports medicine fellow at the University of the University of California, San Francisco.

So, what does increase a runner’s risk for hip or knee arthritis?

Tossing and turning, waking up frequently or lying awake for hours is no laughing matter.

According to the National Sleep Foundation, the average adult should aim for seven to nine hours of sleep each night. Why? The Cleveland Clinic explains that lack of sleep can lead to:

• impaired memory
• relationship stress
• decreased quality of life
• increased risk of a car accident

Chronic lack of sleep, or insomnia, can also lead to serious health issues including:

• high blood pressure
• diabetes
• cardiac issues
• obesity

So, if you are asking yourself why can’t I sleep, here are some tips on getting better shut-eye.

About 1,000 species of mold exist and — as allergy sufferers likely know — they’re everywhere.

Even if you have a mold allergy, it’s possible to make life a little easier, through avoidance, medications and reducing the mold around you, according to a blog from Ochsner Health, a Louisiana-based health system.

A type of fungus, mold produces microscopic spores. Mold spores are constantly floating in the air, which is how they trigger allergic symptoms.

Mold is linked to both allergic rhinitis and asthma, year-round.

It can be found outdoors on rotting logs, in compost piles and on grasses. It grows on plants killed by the cold.

Indoors, it can grow in damp areas like the bathroom, kitchen or attic.

You can keep an arm in a cast from wasting away, researchers say, by working out your free arm.

A small group of young men who performed eccentric contraction exercises with one arm — lowering a dumbbell in a slow and controlled motion — saw a 4% strength improvement in the other arm, even though it was immobilized by a cast at the elbow.

Another group assigned to perform concentric contraction exercises — lifting a dumbbell — only lost about 4% of muscle strength in their immobilized arm, the study results showed.

By comparison, a “control group” that did no exercises suffered a 15% decrease in their immobilized arm during the three-week study.

It was already known that gaining muscle strength in one limb through resistance training will transfer to the same muscle on the opposite side of the body, said lead researcher Ken Nosaka.