Regular use of the painkiller and anti-inflammatory drug ibuprofen may reduce the risk of Parkinson's disease by a third, a major study has found.

People who took the drug at least twice a week had a 38% lower risk of developing the condition than those who used other painkillers, such as aspirin, scientists said.

The findings, based on a review of 136,000 patient records, build on previous studies that also reported an apparent protective effect in those who took the drug.

Alberto Ascherio, who led the study at Harvard School of Public Health, said the possibility that a readily available, over-the-counter drug could stave off Parkinson's disease was "captivating".

Parkinson's disease is caused by the death of brain cells that produce a chemical called dopamine. There are around 120,000 people with Parkinson's in the UK alone, and one in 20 is under the age of 40. The disease causes tremors and difficulty with movement.

In the latest study, Ascherio's team looked at the medical records of more than 37,000 male health workers and nearly 99,000 women who had volunteered for the Nurses' Health Study at the Brigham and Women's Hospital in Boston. Questionnaires had been used to gather information about their use of painkillers, including ibuprofen and aspirin.

In the course of a six-year follow-up study, the researchers identified 156 men and 135 women who went on to develop Parkinson's disease. Their findings appear in the journal, Neurology.

In an accompanying editorial, James Bower, a neurologist at the Mayo Clinic in Rochester, said the study did not mean people should start taking ibuprofen to protect against Parkinson's, because there are long-term health risks from taking the drug, including a higher risk of intestinal bleeding.

Xiang Gao, a co-author on the study, said it was unclear how ibuprofen might protect the brain against Parkinson's disease, but it might help to delay its onset.

Kieran Breen, director of research at the charity Parkinson's UK, said there was no evidence to suggest ibuprofen slows the progression of Parkinson's disease in those already diagnosed with the condition and cautioned against using the drug as a preventative measure. "We would not recommend that people rush to take it, as ibuprofen has many other effects that may be harmful if the drug is taken over a long period of time," he said.

"We know that inflammatory changes in the brain may be involved in the death of nerve cells which causes Parkinson's, particularly in the early stages of the condition. We are currently funding research into this area ourselves at the University of Oxford.

"It's difficult to know exactly what effect ibuprofen may be having on the death of nerve cells in the brain, and how it might affect whether somebody will get Parkinson's. But there would seem from this study to be an interesting link."