CHICAGO - Taking such popular heartburn drugs as Nexium, Prevacid or Prilosec for a year or more can raise the risk of a broken hip markedly in people over 50, a large study in Britain found.

The study raises questions about the safety of some of the most widely used and heavily promoted prescription drugs on the market, taken by millions of people.

The researchers speculated that when the drugs reduce acid in the stomach, they also make it more difficult for the body to absorb bone-building calcium. That can lead to weaker bones and fractures.

Hip fractures in the elderly often lead to life-threatening complications. As a result, doctors should make sure patients have good reason to stay on heartburn drugs long term, said study co-author Dr. Yu-Xiao Yang of the University of Pennsylvania School of Medicine.

“The general perception is they are relatively harmless,” Yang said. “They often are used without a clear or justified indication for the treatment.”