Sleeping pills have questionable clinical effectiveness
20 December 2012
A major study of clinical trial data that had been submitted
by pharmaceutical companies to the US Food and Drug Administration shows
that half of the benefit of taking sleeping pills comes from the placebo
Rresearchers re-analysed results from more than a dozen clinical
trials of the most common type of sleeping tablets, known as Z-drugs
Their findings, published in this week’s British Medical
Journal (17 December 2012), indicate that once the placebo
effect is discounted, the drug effect is of "questionable clinical
Z-drugs drugs are frequently used in the UK and USA as a
short-term treatment for insomnia with almost £25m worth of
prescriptions handed out in Britain each year. However, some health
experts have questioned whether the benefits of Z-drugs justify
their side effects, which can include memory loss, fatigue and
Questions have also been raised about the validity of published
research into the effects of these drugs based on trials sponsored
by pharmaceutical companies themselves.
Academics from the University of Lincoln, Harvard Medical School
and University of Connecticut conducted a meta-analysis of data from
clinical trials of Z-drugs comparing drug effects with placebo
effects. This type of comparison enables researchers to determine
how much of the drug effect comes from the constituents of the drug
itself, and how much is due to other factors (like the placebo
response or regression to the mean).
They used data submitted by pharmaceutical companies to the US
Food and Drug Administration (FDA) for approval of new products.
This included 13 clinical trials containing 65 different comparisons
and more than 4,300 participants.
The FDA collates results from both published and unpublished
studies, enabling researchers to avoid common types of bias (such as
reporting bias) which can undermine other research based on
Lead author Professor Niroshan Siriwardena, from the School of
Health and Social Care at the University of Lincoln, said: “Our
analysis showed that Z-drugs did reduce the length of time it took
for subjects to fall asleep, both subjectively and as measured in a
sleep lab, but around half of the effect of the drug was a placebo
“There was not enough evidence from the trials to show other
benefits that might be important to people with sleep problems, such
as sleep quality or daytime functioning.
“We know from other studies that around a fifth of people
experience side effects from sleeping tablets and one in one hundred
older people will have a fall, fracture or road traffic accident
after using them.
“Psychological treatments for insomnia can work as effectively as
sleeping tablets in the short-term and better in the long-term, so
we should pay more attention to increasing access to these
treatments for patients who might benefit.”
He said future studies of sleeping tablets should investigate a
broader range of outcomes, not just time taken to fall asleep, and
that pharmaceutical companies should be more transparent in
disclosing results from their studies so that researchers can
independently analyse their results.
Tania B Huedo-Medina, Irving Kirsch, Jo Middlemass, Markos
Klonizakis, A Niroshan Siriwardena. Effectiveness of
non-benzodiazepine hypnotics in treatment of adult insomnia:
meta-analysis of data submitted to the Food and Drug Administration.
BMJ 17 December 2012; 345 doi: