“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.
- What is the association between headaches and volume of white matter hyperintensities on magnetic resonance imaging of the brain?
- What are the effects of weaning protocols on the total duration of mechanical ventilation?
- How does the association between physical activity and adiposity plus insulin sensitivity change over time?
- Can maternal plasma DNA sequencing accurately confirm or exclude fetal trisomy 21?
10, 000 step guide to health
Only about a third of men and women in England aged 45-54 meet physical activity recommendations; no wonder that a quarter of people in this group are obese. However, researchers in Australia have suggested that walking 10 000 steps a day—about five miles—might help middle aged people keep their weight down and reduce the risk of type 2 diabetes, a common complication of obesity.
The researchers fitted 592 Tasmanians with pedometers and measured how many steps they took over two days, then did the same thing again five years later. Alas daily step count decreased between these two time points for 65% of participants. However, those who did manage to increase their step count had a lower body mass index, lower waist to hip ratio, and greater insulin sensitivity. The authors estimate that a sedentary person who increases their physical activity so they hit the 10, 000 steps a day target would increase their insulin sensitivity threefold.
The 10, 000 step concept isn’t entirely new—BBC News tested out its feasibility in 2004 and NHS Choices already recommends this approach. What is new in this study is the effect regular walking can have on the risk of diabetes.
Does white matter matter in headache?
Migraine has been associated with an increased prevalence of white matter hyperintensities on brain magnetic resonance imaging. But what about other types of headache?
Tobias Kurth and colleagues have found an association between any history of severe headache, not just migraine, and increasing volume of white matter hyperintensities. Tension-type headaches in particular were implicated. However, migraine with aura was the only type of headache strongly associated with brain infarcts.
This study looked at a cross section of 780 elderly men and women from Nantes, France, 163 of whom reported a history of severe headache and 116 had migraine. There was no evidence that migraine or other severe headaches were associated with cognitive impairment, irrespective of the presence of structural brain lesions.
A meta-analysis published by the BMJ last year found that white matter hyperintensities predict an increased risk of stroke, dementia, and death (BMJ 2010;341:c3666). Kurth and colleagues suggest that further research is needed to determine whether preventive strategies should be tested to avoid these outcomes in people with headache.
Research online: For this and other new research articles see www.bmj.com/research
Strengths and weaknesses of hospital standardised mortality ratios
Alex Bottle and colleagues from the Dr Foster Unit at Imperial College, London, give a clear and detailed account of how their unit derives the hospital standardised mortality ratios (HSMRs) that the NHS in England uses to judge the performance of hospital trusts (doi:10.1136/bmj.c7116). They explain the complexities and potential problems of the data, coding, case mix, and other issues that make critics worry about the use of HSMRs, and include a case study from Mid Staffordshire NHS Trust to illustrate how changes in HSMRs over time may be interpreted.