For those who have been alarmed by recent headlines about the dangers of sleeping pills and red meat, below are links to some further analyses that are worth reading, courtesy of Media Doctor Australia and the NHS Behind the Headlines service.
(Perhaps every GP, hospital and other health service waiting room should advertise these websites to patients).
On sleeping pills
BMJ Open recently published a US study comparing the medical records of more than 10,000 people prescribed sleeping pills and 23,000 similar people who had never been prescribed them. It followed them for an average of 2.5 years and found that people prescribed hypnotics, even at very low doses, were more likely to die than those not prescribed hypnotics. It also found that people prescribed high doses (more than 132 pills a year) were more likely to develop any cancer.
“This research has generated lurid and fear inspiring headlines around the world without good cause.
It’s an excellent example of the difficulty of assigning cause and effect in studies that are ‘observational’ – where the information has not been obtained from a randomized controlled trial.
In observational studies, subjects elect to use a drug (sleeping pills in this case) and those who do are often very different from those who don’t and this can translate into different rates of clinical outcomes (such as death and cancer).
So it can appear that a drug is increasing the death rate when it is in fact because the users of the drug are sicker than non-users. It can be very hard to adjust for these differences as in the study described here.
The researchers have been quite conservative in the interpretation of their findings but there is still a high likelihood that the increased deaths were not due to a direct effect of sleeping medication.
This should have been made clearer in the story and could have been explained by an independent expert. These are complex issues and cannot be dealt with adequately in a short superficial article like this.”
The NHS Behind the Headlines analysis concluded:
“Although a significant association was found, the most important thing to note is that this study cannot tell us that the drugs themselves are the direct cause of higher rates of death and cancer. This is because both the drugs and the risk of death could be associated with other factors, such as lifestyle, alcohol or smoking, which the researchers cannot rule out. While the researchers did make adjustments to account for behaviour and other health problems, these may not fully compensate for their influence.”
The analysis listed several limitations of the study, including that it was unable to control for depression, anxiety and other emotional factors as these diagnoses are confidential in America. As such, mental health illnesses may be an important confounding factor. As well, the study was done on the basis of prescriptions. The researchers did not monitor how many prescriptions were filled, if the medication was taken or if the medication was taken correctly.
However, the analysis said the study raises an important issue and further research into the safety of these medications is required.
On red meat
This paper, published in Archives of Internal Medicine, reported on the results of two prospective cohort studies that followed 37 698 men from the Health Professionals Follow-up Study (1986-2008) and 83 644 women from the Nurses’ Health Study (1980-2008) who were free of cardiovascular disease and cancer at baseline. Diet was assessed by validated food frequency questionnaires and updated every 4 years.
The study found that red meat consumption was associated with an increased risk of total mortality, and also cardiovascular and cancer mortality. Substituting other healthy protein sources for red meat was associated with a lower mortality risk.
The NHS Behind the Headlines analysis concluded:
“This study had several strengths including its size, long follow-up period and detailed and repeated assessments of people’s meat intake. It also adjusted the results for other factors that might affect risk of mortality. However, relying on participants to self-report factors, such as their meat intake through questionnaires, introduces the possibility of error, although the questionnaires were validated. Furthermore, participants were mainly white health professionals, so the results may not be relatable to other populations.”
The analysis said that newspaper reports stating the research proved that “regular consumption of red meat ‘kills’” were wrong. It said: “This was a well-conducted study but it could not conclusively prove that red meat raises the risk of premature death, although the results are of key interest and the evidence is mounting on the issue.”
The analysis noted that red meat is a good source of protein and certain nutrients such as iron, some vitamins and zinc, but it is already recognised that it is likely to raise the risk of cancer especially bowel cancer.
As a by the by, the red meat industry has spent a small fortune on advertisements in the medical press in Australia in recent years, promoting the benefits of red meat in the diet.
The NHS site links to advice about recommended consumption of red meat, with tips on how to cut down.