In a review of 11 international studies, researchers found that health providers' skills in advanced life support typically deteriorated six months to a year after training, based on test performance. That's concerning, since the standard guideline calls for re-training every two years, note the researchers, led by Dr. Matthew Huei-Ming Ma of National Taiwan University Hospital. Many experts have long believed that re-training at two-year intervals is "not optimal," said Dr. Lance Becker, director of the Center for Resuscitation Science at the University of Pennsylvania in Philadelphia. But individual medical centers are taking their own steps, he said.