I see this study is spawning sensationalist headlines all over the internet. Of course, many of the news stories overlook the distinction between causation and correlation, and observational vs. clinical trials.
I dug into the original study since I occasionally take these drugs and would prefer not to be contributing to my early demise. Study is here: (Hypnotics' association with mortality or cancer: a matched cohort study -- Kripke et al. 2 (1) -- BMJ Open
The doctor is quite a character. In his ebook (Chapter 1, Sleeping Pills Could Shorten Your Life - The Dark Side of Sleeping Pills, an eBook by Daniel F. Kripke, MD.
) he outright states that "sleeping pills cause cancer in people", based on animal data and his interpretation of the clinical trials submitted to the FDA for regulatory approval. He suspects the drug co's and the FDA of a massive cover-up.
I can't rule that out, of course, but his review contains several flaws, IMO. First, it was based on a narrow segment of patients in rural Pennsylvania, with data drawn from an HMO's medical records: "The population is mostly of low socio-economic status, having less than high school education and less than one-third are insured under the Geisinger Health Plan."
Second, while he attempted to control for the effects of disease, health status, etc, "We were unable to control for depression, anxiety and other emotional factors because of Pennsylvania laws protecting the confidentiality of these diagnoses".
Third, this was an observational study only, not a controlled, clinical study: "Accordingly, we were unable to verify that the medications ordered were dispensed by a pharmacy, and, if dispensed, whether the patient ingested the prescribed hypnotic". Although he concludes that this would lead to an underestimation of the drugs' lethality.
He addresses these limitations, yet still concludes that these drugs "kill people". I can easily come up with other hypotheses to explain his results. For example, I can speculate that poor, uneducated patients in an economically depressed region may suffer from extreme stress, or subclinical depression. Maybe their overworked HMO docs prefer to write prescriptions and move on to the next patient, rather than screen for depression, or anxiety, or refer to an psychologist for further evaluation. Maybe the HMO doesn't even allow that. Or maybe other undiagnosed illnesses, or aches and pains brought on by a life of hard physical labor led to both insomnia and an early death. I don't know, but I'm not sure he does, either.
I'm not defending the meds -- they may very well be more dangerous than current thinking suggests -- but I'm not completely buying his conclusion, either.
As they say in medical research, further study is needed.