People are relying on sleeping pills more than ever to get a good night’s rest, but a new study by Scripps Clinic researchers links the medications to a 4.6 times higher risk of death and a significant increase in cancer cases among regular pill users.

The results, published by the open-access online journal BMJ Open, cast a shadow over a growing segment of the pharmaceutical industry that expanded by 23% in the United States from 2006 to 2010 and generated about $2 billion in annual sales.

The research is the first to show that eight of the most commonly used hypnotic drugs were associated with increased hazards of mortality and cancer, including the popularly prescribed medications zolpidem (known by the brand name Ambien) and temazepam (Restoril), said author Daniel F. Kripke, MD, of the Viterbi Family Sleep Center at Scripps Health in San Diego. Those drugs had been thought to be safer than older hypnotics because of their shorter duration of action.

Study participants who took sleeping pills were matched with control patients of similar ages, gender, and health who received no hypnotics in order to eliminate the possibility that other factors led to the results.

Even among patients who were prescribed one to 18 sleeping pills per year, the risk of death was 3.6 times higher than among similar participants who did not take the medications. The study looked at patients aged 18 years and older, and found the increased risk in all age groups.

Rates of new cancers were 35% higher among patients who were prescribed at least 132 hypnotic doses a year as compared with those who did not take the drugs.

Using data stored in an electronic medical record that has been in place for more than a decade, the researchers obtained information on almost 40,000 patients cared for by a large integrated health system in the northeastern United States.

The study included 10,531 sleeping pill users who were prescribed the medications for an average of 2.5 years and 23,674 control participants who were not prescribed the drugs. Information came from outpatient clinic visits conducted between January 1, 2002, and September 30, 2006.

“It is important to note that our results are based on observational data, so even though we did everything we could to ensure their validity, it’s still possible that other factors explain the associations,” said coauthor Lawrence E. Kline, DO, who is medical director of the Viterbi Family Sleep Center. “We hope our work will spur additional research in this area using information from other populations.”