Here’s a stunning statistic: A prescription for just a few sleeping pills per year was associated with a 3.6 times increased risk of dying (from any cause) compared to those who didn’t have any prescriptions for these medications. It jumped to 5.32 if more than 152 doses per year were prescribed. The authors of this British Medical Journal article estimate that in 2010, hypnotics may have been associated with 320,000 to 507,000 excess deaths in the US alone. They came to this conclusion by combing through more than 10,000 records of people who were prescribed at least one prescription for a hypnotic and looked at mortality over 4 years compared to matched controls who didn’t have a hypnotic prescription.
They were careful to note that association does not imply causality. While it’s temping to interpret this study implying that sleeping pills can kill people, it’s important to realize that there are numerous studies showing that people with sleep problems are known to have a higher risk of dying from various reasons. For example, people with insomnia have higher rates of depression, suicide, and cancer. In addition, a significant number of insomniacs on sleeping pills will have obstructive sleep apnea, and untreated obstructive sleep apnea can increase your risk of car accidents, heart attack and stroke.
It’s likely that increased risk of dying is already elevated in people with sleep problems, and those that are given sleeping pills are found to have increased rates of death. This may be the classic case of being true, true, but unrelated. To really determine what causes what, you’ll have to look at mortality in a large prospective study in people with insomnia and randomize to be given sleeping pills versus a placebo.