UNITED STATES - Long-term use of a drug commonly prescribed for anxiety and sleeplessness is linked to a greater risk of Alzheimer's, a study said on Wednesday.
Whether chronic use of benzodiazepines actually causes the brain disease is unknown, but the link is so glaring that the question should be probed, its authors said.
Dementia affects about 36 million people worldwide, a tally that is expected to double every 20 years as life expectancy lengthens and the "baby boom" demographic bulge reaches late age.
Researchers in France and Canada, using a health insurance database in Quebec, identified 1,796 people with Alzheimer's whose health had been monitored for at least six years before the disease was diagnosed.
They compared each individual against three times as many healthy counterparts, matched for age and gender, to see if anything unusual emerged.
They found that patients who had extensively used benzodiazepines for at least three months in the past, were up to 51 per cent more likely to be diagnosed with Alzheimer's. The risk rose the longer the patient had used the drug.
The investigators admitted the picture was foggy.
Benzodiazepines are used to treat sleeplessness and anxiety -- symptoms that are also common among people just before an Alzheimer's diagnosis.
In other words, rather than causing Alzheimer's, the drugs were being used to ease its early symptoms -- which could explain the statistical association, they said.
"Our findings are of major importance for public health," and warranted further investigation, said the team.
"(...) A risk increase by 43-51 per cent in users would generate a huge number of excess cases, even in countries where the prevalence of use of these drugs is not high."
The paper, published by the British Medical Journal (BMJ), is led by Sophie Billioti de Gage at the University of Bordeaux, southwestern France.
In a comment, Eric Karran, head of research at Alzheimer?s Research UK, said the study gathered data over a five-year period only, whereas Alzheimer's symptoms often appear a decade or more before diagnosis.
"It is difficult to tease out cause and effect in studies such as this," he said.
"We need more long-term research to understand this proposed link and what the underlying reasons behind it may be."