Researchers have found evidence that children who spent the most time outdoors were the least likely to suffer from myopia, also called nearsightedness or shortsightedness. Myopia has become increasingly common in recent decades, with more than 80 percent of people in some groups being nearsighted.

Researchers looked at more than 4,000 children in two age groups. They found that among 12-year-olds, those who spent more than 2.8 hours outside every day were less likely to be myopic.

In contrast, children who spent less than 1.6 hours outdoors every day and more than 3.1 hours in near-work activity had double to triple the likelihood of being nearsighted.

“What doesn’t kill you makes you stronger” is a phrase that contains more than a grain of truth. It describes the theory of hormesis — the process whereby organisms exposed to low levels of stress or toxins become more resistant to tougher challenges.

The theory of hormesis has been around for decades, but has long been met with skepticism or downright suspicion. In recent years, however, biologists have pieced together a clear molecular explanation of how it works, and hormesis has finally been accepted as a fundamental principle of biology and biomedicine.

As an example, exposing mice to small doses of gamma ray radiation shortly before irradiating them with very high levels of gamma rays actually decreases the likelihood of cancer. A similar effect occurs when dioxin is given to rats.

The biochemical mechanisms by which hormesis works are not well understood. It is thought that a low dose of a toxin can trigger certain repair mechanisms in the body, and these mechanisms, having been initiated, are efficient enough that they not only neutralize the toxin’s effect, but can even repair other defects not caused by the toxin.

One of the areas where the concept of hormesis has been explored extensively is aging. It is thought that exposing cells to mild stress could result in the adaptive or hormetic response that has anti-aging effects. Some of the mild stresses that might work for this include heat shock, irradiation, pro-oxidants, hypergravity, food restriction, and even exercise.

The obesity rate in the U.S. has more than tripled among 6 to 11-year-olds over the past three decades. A new study indicates that cutting down on REM sleep, a deep restorative form of rest, is associated with obesity among teens and children.

In the study, 335 children and teens were observed in a sleep clinic during three consecutive nights. The children who slept the least were the most likely to be overweight, and the less REM sleep they got, the greater the likelihood of obesity.

It could be that sleep loss changes the hormone levels in the body that may impact how much a person eats during the waking hours. Exhaustion may also influence levels of exercise.

Children whose mothers used cell phones frequently during pregnancy are more likely to have behavior problems, especially if they themselves are cell phone users.

A team of scientists looked at a group of more than 13,000 children. When the children reached age 7, mothers were asked to complete a questionnaire about their own cell phone use in pregnancy and their child’s use of cell phones, as well as their children’s behavior and health.

Children with both prenatal and postnatal cell phone exposure were 80 percent more likely to have emotional problems, conduct problems, hyperactivity, or problems with peers. Children who were only exposed prenatally also had a higher likelihood of behavior problems, but not as high as those who were also cell phone users.

Thinking about buying some handy ‘germ fighting’ dish soap or bathroom cleanser? Think again. In all likelihood, those cleaners contain triclosan, a toxic pesticide that’s marketed as an “antibacterial agent” but is powerful enough to threaten children’s health and pollute mothers’ breast milk. According to a study by researchers at the non-profit Environmental Working Group (EWG), triclosan has been: * linked to cancer in lab animals * targeted for removal from some stores in Europe for it