People who take anxiety and/or sleeping pills have an increased risk of developing Alzheimer's, according to a recent study.

Researchers found that people who used benzodiazepine for at least three months were up to 51 percent likely to develop the brain disorder, BBC News reported. NHS said the drug should be used for eight to 12 weeks at most.

 "Benzodiazepine use is associated with an increased risk of Alzheimer's disease," lead researcher, Sophie Billioti de Gage of the University of Bordeaux, France, and colleagues wrote in the study. "Unwarranted long-term use of these drugs should be considered as a public health concern."

For the study, researchers examined 2,000 cases of Alzheimer's disease in adults 66 years or older living in Quebec. All had been prescribed benzodiazepines. Those cases were compared to about 7,000 healthy people of the same age living in the same community.

The research team also found a dose-response relationship between the benzodiazepine and the neurodegenerative disorder. The risk of developing the most common form of dementia was higher in people with longer exposure of long-acting benzodiazepines than those exposed to short-acting ones.

"This study shows an apparent link between the use of benzodiazepines and Alzheimer's disease although it's hard to know the underlying reason behind the link," Dr. Eric Karran, director of research at Alzheimer's Research UK, told BBC News.

Karran said that one limitation of the study "is that benzodiazepines treat symptoms such as anxiety and sleep disturbance, which may also be early indicators of Alzheimer's disease."

The findings were recently published in the British Medical Journal.