TUESDAY, Sept. 9, 2014 (HealthDay News) -- Older adults who habitually use sedatives for anxiety or insomnia may have a heightened risk of developing Alzheimer's disease, a new study suggests.

The drugs in question are benzodiazepines, a widely prescribed group of sedatives that include lorazepam (Ativan), diazepam (Valium) and alprazolam (Xanax). Older adults commonly take the drugs for anxiety or insomnia, often long-term, according to background information in the study.

That's despite the fact that guidelines call for only short-term use of the drugs, at most. In 2012, the American Geriatrics Society (AGS) put benzodiazepines on its list of drugs considered "potentially inappropriate" for seniors, because of risks like confusion, dizziness and falls.

The current study isn't the first to link benzodiazepines to Alzheimer's risk, but it adds to evidence that longer-term use of the drugs -- beyond three months -- might be a risk factor, according to lead researcher Sophie Billioti de Gage, a Ph.D. candidate at the University of Bordeaux, in France.

"For people needing or using benzodiazepines, it seems crucial to encourage physicians to carefully balance the benefits and risks when renewing the prescription," Billioti de Gage said.

But the study was only able to find an association between the drugs and Alzheimer's risk. It wasn't designed to definitively prove that the drugs caused the memory-robbing condition, according to geriatrics specialist Dr. Gisele Wolf-Klein, who was not involved in the research.

One reason is that the findings are based on prescription records. "We know the drugs were prescribed, but we don't know how often people took them, or if they took them at all," said Wolf-Klein, director of geriatric education at North Shore-LIJ Health System in New Hyde Park, N.Y.

Regardless, she said, benzodiazepines have enough known risks to warrant concern.

"There is absolutely no doubt these drugs have dangerous side effects," Wolf-Klein said. "It's important for people to understand that they can be addictive, and increase the risk of confusion and falls."

The study was published online Sept. 9 in BMJ.

For the study, Billioti de Gage's team examined the histories of nearly 1,800 older adults with Alzheimer's, comparing each one with four dementia-free people of the same age and sex.