Research highlights – 3 June 2011

Research questions“Research highlights” is a weekly round-up of research papers appearing in the print BMJ. We start off with this week’s research questions, before providing more detail on some individual research papers and accompanying articles.

Sleep and size
Two papers in this week’s BMJ deal with the relation between obesity and sleep. Philippa Carter and colleagues’ study of young children (age 3-7) found that those who slept less were more likely to have a higher body mass index and greater fat mass in later childhood, even after adjustment for several potential confounding factors. These results strengthen the evidence for a causal link between sleep and body fat. In a linked editorial Francesco Cappuccio and Michelle Miller discuss possible mechanisms, along with the strengths and limitations of the study.

Meanwhile, being obese as an adult is associated with sleep apnoea, and some evidence suggests that losing weight can improve the condition. In a recent randomised controlled trial Kari Johansson and colleagues found that a very low energy diet improved moderate to severe sleep obstructive apnoea in obese men. However, a linked editorial commented that “The trial was only nine weeks long, which leaves open the question of the long term sustainability of the weight loss.”

Addressing this question, the group has now followed up the trial participants for a year—during which the patients took part in a weight loss maintenance programme—and found that the initial reduction in severity of obstructive sleep apnoea was largely maintained. About half the 63 patients no longer required continuous positive airway pressure; and a tenth had total remission. Patients who lost most weight improved the most, as did those who had the worst sleep apnoea at baseline. This week’s Clinical Review gives more guidance on how to treat patients with sleeping difficulties caused by sleep apnoea and other problems.

Surgical disc prosthesis for chronic low back pain
Christian Hellum and colleagues compare the efficacy of surgery with disc prosthesis versus intensive rehabilitation for patients with chronic low back pain and degenerative intervertebral disc changes. The rehabilitation combined physical and psychological elements, and such programmes have become standard treatment for chronic back pain in many countries. The authors found that patients undergoing disc prosthesis improved more in the primary outcome (disability and pain) than patients treated with rehabilitation, but after two years the result was not clinically significant.

However, the authors and the accompanying editorial by Jeremy Fairbank point out that surgery carries considerable extra risk (including a leg amputation in this study during surgical revision of a dislodged polyethylene disc). Professor Fairbank argues that it seems only sensible that, in the rare cases when back pain does not resolve and becomes chronic, a rehabilitation programme should be tried before resorting to surgery. However, if there is still no improvement and surgery is warranted, then disc replacement seems a promising alternative to spinal fusion.

Clinical risks of overcrowded emergency departments
Might Astrid Guttmann and colleagues’ retrospective cohort study in Ontario also inform the debate on waiting times in A&E in the NHS? The authors used routine data and record linkage to assess the risk of adverse events among nearly 14 million people who were triaged by nurses at 125 busy Ontario emergency departments in 2003-8  and were either “seen and discharged” or “left without being seen [by a doctor].” Triage scores were grouped as high acuity (1-3: needing resuscitation, emergent, and urgent) and low acuity (4-5: less urgent and non-urgent). Absolute rates of death and admission to hospital within the next seven days were very low at 0.07% and 1.8%, adjusted for important confounders affecting patients, shift, and hospital. But the relative risks are still notable and worrying: for high acuity patients who waited ≥6 versus <1 hour, the adjusted odds ratios were 1.79 (95% confidence interval 1.24 to 2.59) for death and 1.95 (1.79 to 2.13) for admission, and long waits carried similar risks for low acuity patients. More than 600,000 people left without being seen, and clearly made the right decision, as they had no excess risk in the following week.

Editorialist Melissa L McCarthy applauds the study and calls for better tracking of patients’ health (and not just their satisfaction) after discharge from emergency departments.