CHICAGO – Regular use of over-the-counter pain relievers might help delay or prevent Parkinson’s disease, the neurological disorder that affects more than half a million Americans, research suggests.

The risk of developing the disease was 45 percent lower in people who used drugs such as ibuprofen and naproxen at least twice weekly than it was in nonusers, according to a review of two large studies.

If replicated in more rigorous research, the findings are potentially significant since there is no proven treatment to prevent or delay the onset of Parkinson’s, said lead author Dr. Honglei Chen, a Harvard School of Public Health instructor.

The results, however, are too preliminary to warrant recommending painkillers to prevent Parkinson’s, Chen said.

His research appears in August’s Archives of Neurology, published Monday.

The report echoes laboratory research in animals suggesting that drugs known as nonsteroidal anti-inflammatories, or NSAIDS, might help protect against Parkinson’s.

The new data, based on an analysis of two studies of health professionals, are the first to suggest similar results in humans, Chen said.

The analyzed studies involved a total of 142,902 health professionals who provided periodic information on their medical history and lifestyle habits for more than 10 years. Participants were aged 30 to 75 at the outset and were asked about use of NSAIDS including ibuprofen, indomethacin, naproxen and diflunisal. Use of aspirin, also an anti-inflammatory, was determined separately.

Parkinson’s disease was diagnosed in 415 participants. The risk of developing the disease was 45 percent lower in those who used NSAIDs other than aspirin at least twice weekly.

A similar risk reduction was found in those who used aspirin two or more times daily, but no benefit was found with less aspirin use.

Information on exact dosages wasn’t available.

The findings suggest that doctors would need to treat 98 people with anti-inflammatory drugs for about 10 years to prevent one additional case of Parkinson’s.

About 50,000 mostly middle-aged and older Americans are diagnosed with Parkinson’s each year, and the prevalence is expected to increase with the burgeoning numbers of older Americans.

The disease occurs when nerve cells degenerate in a portion of the brain that controls muscle movement. Symptoms might include tremors in the hands, arms or legs and a stiff walking gait. They tend to worsen over time and might impair daily functioning.

There is no cure, but medication can help control symptoms.

Evidence suggests that inflammation might be involved in Parkinson’s nerve-cell degeneration, and Chen’s study is “the first convincing epidemiological data for a therapeutic benefit” for Parkinson’s from NSAIDs, according to an Archives editorial by Dr. Mya Schiess of the University of Texas-Houston Medical School.

Schiess noted that the study participants were relatively young and said that greater benefits might be seen in older patients at greater risk for Parkinson’s because of age.

But because NSAIDs can cause gastrointestinal bleeding and other problems, more research is needed to determine if any anti-Parkinson’s effects they may provide outweigh the risks, Schiess said.

Parkinson’s researcher Michael Zigmond at the University of Pittsburgh called the study “very promising” with a potentially huge impact.