Ibuprofen could reduce the risk of developing Alzheimer's disease, suggests a US study group.
Data from almost 250,000 long term users showed those who used the painkiller for more than five years were more than 40% less likely to develop Alzheimer's.
The study in Neurology reported that some other similar painkillers may also have a protective effect.
They looked at five years of data in 49,300 people over the age of 55 years who had developed Alzheimer's disease and almost 200,000 controls
Dementia experts said the results were interesting but warned against people taking ibuprofen to reduce their risk.
It is not the first time an association between non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, and Alzheimer's disease has been reported but results have been conflicting.
The researchers from Boston University School of Medicine said one possible reason for inconsistent reports may be that different NSAIDs have different effects.
They looked at five years of data in 49,300 people over the age of 55 years who had developed Alzheimer's disease and almost 200,000 controls.
Overall, use of NSAIDs for five years was associated with a 24% reduced risk of developing Alzheimer's.
But the effects of ibuprofen were the most profound and some other NSAIDs, such as celecoxib, had no effect.
The study leader said ibuprofen had been shown in animal models and the laboratory to reduce levels of protein deposits associated with Alzheimer's in the brain.
On findings that other NSAID's not returning the same results the Doctor suggested the results were probably partly due to direct effects of the drug and partly due to the fact ibuprofen is the most commonly used NSAID thus the finding would be picked up more easily.
The study group advised that as all NSAIDs have well known side-effects that can be very serious further trials were needed to make sure the risks and benefits were clarified.
The Alzheimer's Society announced they felt the research built on evidence of the protective effects of long-term use of NSAIDs against Alzheimer's disease.
Cautioning that whilst this is important research it does not mean that people should start taking ibuprofen to reduce their risk of developing dementia.
The Alzheimer's Research Trust, added the results were promising.
Again cautioning, the apparent connection between ibuprofen and a reduced risk of dementia is no silver bullet, but indicates an exciting direction for future research," she said.
In a separate study again published in Neurology research showed people with shorter arms and legs may be at a higher risk for developing dementia later in life, the US researchers said poor nutrition in early life was the link between the two.