Heading the ball is a key soccer skill, but a new study finds that players who headed the ball frequently were more likely to suffer brain injury and damage their memory than their fellow players who were a little less headstrong, so to speak.

While sports like football (the American variety) and hockey garner most of the attention when it comes to concussions and other forms of traumatic brain injury, or TBI, soccer is an intense physical sport for which the head can be as important as the foot. But since research hasn't linked heading to concussions, players, coaches and medical professionals have generally stayed on the sidelines with regard to its risks.

"For many people, it's beyond belief that minor injuries could be a problem," said Dr. Michael Lipton, a neuroradiologist at the Albert Einstein College of Medicine in New York City and lead author of the study published online by the journal Radiology.

To investigate the issue, Lipton and his colleagues interviewed 37 adult league soccer players from New York City and took high-tech scans of their brains using an MRI technique called diffusion tensor imaging.

The relationship between heading and traumatic brain injury was not simply a linear one, with more heading leading to more injury. Instead, the researchers discovered that players could safely head the ball 885 to 1,550 times a year without experiencing problems; the threshold was almost 1,800 headers for memory-related difficulty.

Lipton suggests that soccer start keeping a "head count" to monitor the number of headers players use in a given game. The head count would be analogous to the "pitch count" in baseball that ensures pitchers don't throw too many pitches in a single outing.

Los Angeles Times

Drug-injecting addicts who took a daily antiretroviral pill were half as likely to become infected with HIV as those who did not, a major new study has found, providing that final piece of evidence that such treatments can prevent AIDS in every group at risk. Earlier clinical trials showed that the therapy can sharply reduce the risk of HIV transmission from mother to child, and in gay and bisexual men and heterosexuals.

"This provides the totality of the evidence that the drugs used to treat the infection are also very effective at preventing it," said Dr. Salim S. Abdool Karim, a prominent South African AIDS researcher who also wrote a commentary in the Lancet, which published the study.

The growing number of clinical trials showing that antiretrovirals can prevent HIV infection means the drugs are increasingly seen as another in the arsenal of weapons against AIDS, along with condoms, abstinence and fidelity, early antiretroviral treatment, male circumcision in Africa, microbicide gels and other options.

The formal results of the study, done on 2,400 drug users in Thailand, showed that taking a tenofovir pill each day — a therapy known as pre-exposure prophylaxis, or PrEP — reduced infections by 49 percent. Addicts who took the pills regularly, based on measures of tenofovir in their blood, were 74 percent less likely to become infected.

"This is an exciting day," said Dr. Jonathan Mermin, director of HIV prevention for the Centers for Disease Control and Prevention in Atlanta. "This culminates a decade of PrEP research."

New York Times

120,000-year-old cancer found in rib

A Neanderthal who lived more than 120,000 years ago had cancer of the bones, in the earliest known incidence of the disease found in the human fossil record, a study reports. The bone tumor, which was discovered in the rib of a Neanderthal specimen found in present-day Croatia, is described in the journal PLoS One.

David W. Frayer, an anthropologist at the University of Kansas and one of the researchers involved in the study, said it is unclear how the tumor affected the overall health of the individual. "Tumors in the archaeological or fossil record are extremely rare," he said. "This shows that they were susceptible to some of the same cancers we are today, even in a nonpolluted environment."

New York Times