Health briefs: Lung cancer is top killer of women

The reason is smoking, which peaked years later for women than it did for men. Lung cancer has been the top cancer killer for men for decades. "We're seeing the deaths now" from lung cancer due to a rise in smoking by women three decades ago, said Lindsey Torre of the American Cancer Society.

However, smoking rates have leveled off or dropped in rich countries.

Hearts, kidneys and other donated organs have added more than 2 million years to the lives of the American patients who received them, according to a new analysis.

That tally, published by the journal JAMA Surgery, covers 25 years of U.S. organ donation. Researchers started with 1987, the year when the United Network for Organ Sharing began keeping track of all U.S. organ transplants.

Between Sept. 1, 1987, and Dec. 31, 2012, 533,329 patients received a donated organ (or perhaps two). Another 579,506 patients were put on the waiting list but didn't get an organ. By comparing the outcomes for patients in both groups, the researchers were able to calculate how much longer the transplant recipients lived as a result of their new organs. So far, that number adds up to 2,270,859 years — a "stellar accomplishment," said the study authors. And that number will keep getting bigger as long as any of the transplant recipients are still alive.

Stomach and urinary tract infections may have a bright side: A study reports that they are associated with a reduced risk for rheumatoid arthritis.

Previous reports have suggested a connection between infection and rheumatoid arthritis, and this study aimed to test how infections at different sites might be involved.

Those who reported gastroenteritis were 29 percent less likely to have arthritis, urinary infections 22 percent less likely, and genital infections 20 percent less likely than those who did not. In contrast, there was no association with any respiratory infection — sinusitis, tonsillitis or pneumonia.

Chronic cocaine use alters brain circuits that help us learn from mistakes, a study suggests. The study, published online in the Journal of Neuroscience, could offer a biological marker for the cycle of destructive decisions that many addicts exhibit.

Researchers measured EEG signals from a region of the midbrain that has been associated with how the brain manages errors in reward prediction. Neurons there release and absorb more dopamine when things go better or worse than expected, and less when events meet expectations.

"The brain learns from it — whether you should go ahead with this experience the next time or you should stay away from it," said lead researcher Muhammad Parvaz, a cognitive neuroscientist at the Icahn School of Medicine at Mount Sinai in New York.

Among chronic users, said Parvaz, "the worse-than-expected response was not there." Their management of negative reward error prediction was impaired. This could explain why addicts will return to drugs despite the negative impacts of incarceration and loss of money, friends and family, researchers said. "They don't learn from it," Parvaz said.