Some older women are more likely to suffer debilitating hip fractures if they take certain indigestion drugs, U.S. researchers say.

The risk of hip fracture was 1.35 times higher among post-menopausal women who regularly took drugs used to treat heartburn and acid reflux for two years compared with those who did not take the medication.

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Hip fractures can result from a motor vehicle collision, sports injury or fall from a height. (iStock)

The study published in Wednesday's issue of the British Medical Journal followed nearly 80,000 postmenopausal women participating in the U.S. Nurses Health Study from 2000 to 2008. Since that project started in 1976, analysis of the nurses' medical records and questionnaires every two years have provided insight into health and lifestyle risks for women ranging from breast cancer to alcohol use.

The findings suggested that women who took the heartburn drugs, known as proton pump inhibitors, and smoked could face more than 1.50 times higher risk of fracture.

In May 2010, the U.S. Food and Drug Administration warned of hip fractures among those taking PPIs but concluded that more data was needed for a full analysis.

While several other studies have raised concerns about the long-term use of proton pump inhibitors and risk of hip fractures, the results were conflicting and many lacked information on important diet and lifestyle factors that could make a difference.

Proton pump inhibitors are among the most commonly used drugs worldwide, the researchers said.

Use of the drugs increased in the U.S. after they became available without a prescription.

In the latest study, Hamed Khalili of Massachusetts General Hospital and his co-authors took menopausal status, body weight, physical activity levels, smoking, alcohol consumption and use of calcium supplements into account in their analysis.

Hip fractures from low and moderate traumas such as falling on ice or off a chair were included. High traumas such as skiing accidents or falling down the stairs were not.

Hip fracture risk fell after drugs stopped

Over the eight-year study period, there were 893 hip fractures among the participants.

Compared with use of proton pump inhibitors, regular use of a milder antacid called H2 blockers was tied to a "more modest" risk of fracture of 1.23 times higher, the researchers said.

Given that use of proton pump inhibitors is on the rise, the estimates suggest the drugs could be contributing to a "high burden of fractures," they concluded.

The risk of hip fracture returned to normal two years after women stopped taking proton pump inhibitors, the researchers said.

The study's authors acknowledged drawbacks of the study, such as not having specific information on the type or brand of proton pump inhibitors used. They didn't confirm hip fractures against medical records, but said the nurses are extremely reliable at reporting the injuries.

The study was funded by the U.S. National Institutes of Health.