Benzodiazepines are widely used by older people in developed countries and often for long periods. In a case-control study, researchers investigated the relationship between past benzodiazepine use and the risk of Alzheimer's disease in a representative sample of older (older than 66 years) community-dwelling residents in the province of Quebec, Canada. Using a province-wide health insurance claims database, they identified 1,796 cases with a first diagnosis of Alzheimer's disease during the study period and matched them with 7,184 controls. Researchers examined records in both groups from at least six years before the index date. Exposure to benzodiazepines was defined as the cumulative dose expressed as prescribed daily doses and the drug-elimination half-life.

A total of 894 patients with Alzheimer's disease and 2,873 controls had used benzodiazepines at any time. Long-term use (more than 180 prescribed daily doses or cumulative exposure over six months) was markedly higher among cases (33%) than controls (22%).

Use of benzodiazepines at any time increased the risk of Alzheimer's disease by 43% to 51%. No association was found for exposures of up to three months, but there did appear to be a dose-response effect. Risk increased with cumulative exposure and with use of long-acting benzodiazepines. Adjustment for anxiety, depression, and insomnia, which are possible prodromes (early symptoms) of dementia, didn't change the results.

The authors write that the risks and benefits should be carefully considered when prescribing benzodiazepines and that treatment should be of short duration and preferably with short-acting agents, in accordance with good-practice guidelines.

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