“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.

• How is chronic kidney disease stage associated with risk of major cardiovascular disease and non-vascular mortality among apparently healthy adults?
• Does a low estimated glomerular filtration rate predict risk of stroke and, if so, to what extent?
• Does preventive treatment with β blockers, brief behavioural therapy, or their combination improve outcomes of an optimised acute migraine drug regimen?
• Are common pathogenic bacteria associated with acute wheezy episodes in young children and, if so, is the association independent of viral infection?
• What sociodemographic patterns of risk factors for non-communicable diseases are seen in rural Indian people?

Kidney disease and vascular disordersTwo pieces of research published in the BMJ this week look at the importance of chronic kidney disease in determining a patient’s risk of coronary heart disease and stroke.

The first study, by Emanuele Di Angelantonio and colleagues, found that even the earliest stages of chronic kidney disease are linked to a higher risk of coronary heart disease. The second study, by Meng Lee and colleagues, discovered that the risk of incident stroke among people with an estimated glomerular filtration rate of less than 60 ml/min/1.73 m2 (normal range 100-130 ml/min/1.73m2) was 43% higher than in those with an estimated glomerular filtration rate of 60-90 ml/min/1.73 m2.

These two studies were quite different in design and scope: the first was a prospective cohort study in 16 958 individuals from Reykjavik, Iceland, whereas the second was a retrospective meta-analysis, but of prospective studies, including 284 672 participants from a variety of countries like the United States and Japan. Both, however, add important information on risk stratification of patients with chronic kidney disease.

Preventing migraine

As the United States gets to grips at last with the concept and practice of comparative effectiveness research (doi:10.1136/bmj.c3615) the BMJ continues to prioritise randomised controlled trials that compare different treatments head to head, rather than simply against placebo. Kenneth A Holroyd and colleagues from Ohio did such a trial in patients with at least three disabling migraines a month despite taking “optimal” treatment with a 5-HT1B/D agonist or triptan, plus an NSAID or antiemetic drug as required. Participants were randomised to one of four added treatments: preventive (β blocker) treatment, placebo, behavioural migraine management (comprising group education, relaxation, and cognitive behaviour therapy) plus placebo, or behavioural migraine management plus preventive treatment. For the group that received a β blocker plus behavioural management, compared with each of the three remaining treatments, the number needed to treat to at least halve the number of migraines a month ranged between 2.6 and 3.1.

Is it just a viral wheeze?

Received wisdom is that there’s no need to prescribe antibiotics for wheeze in young children because any underlying infection is probably viral. But Hans Bisgaard and colleagues’ analysis from the Copenhagen Prospective Study on Asthma in Childhood provides evidence to the contrary. They examined around 900 throat aspirate samples from about 300 wheezing babies and toddlers and found that wheezy episodes defined—at medical examination— as audible wheeze, prolonged expiration, or ronchi on auscultation were significantly and independently associated with both viral infection and bacterial infection (mostly from H influenzae, M catarrhalis, and S pneumonia). The authors now recommend randomised clinical trials to evaluate the effectiveness of antibiotics in wheezy children.

Research online: For these and other new research articles see www.bmj.com/channels/research.dtl

England-wide variation in rates of caesarean section
Adjusted rates of caesarean section in England vary from 14.9% to 32.1% of singleton births, according to Fiona Bragg and colleagues (doi:10.1136/bmj.c5065). Their evaluation of hospital episode statistics from 146 English NHS trusts pinned the cause of this variation on differences in the rates of emergency caesarean section between trusts.

Cerebral palsy and Apgar score
Kari Kveim Lie and colleagues’ study of 543 064 singleton births in Norway has shown that low Apgar score (<4) 5 minutes after birth is strongly associated with cerebral palsy diagnosed before the age of 5 years (doi:10.1136/bmj.c4990). Interestingly, the association was stronger in children with normal birth weight (2500 g) than in children with low birth weight (<1500 g).