Short Cuts

All you need to read in the other general journals

BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e401 (Published 18 January 2012) Cite this as: BMJ 2012;344:e401

Cardiac arrests are rare during competitive long distance runs

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Nearly 11 million people ran marathons or half marathons in the US between 2000 and 2009. Fifty nine had a cardiac arrest during or just after the race, and 42 of them died, according to a new study. Cardiac arrests were more common in men (0.90/100 000; 95% CI 0.67 to 1.18) than women (0.16, 0.07 to 0.31), and more arrests occurred during or after marathons (1.01/100 000; 0.72 to 1.38) than half marathons (0.27, 0.17 to 0.43).

The authors found their 59 cases through a comprehensive search of online resources, including race websites, local newspapers, and public search engines. They wrote to survivors and next of kin for more details and analysed medical records. Runners who arrested had a mean age of 42 years, but those who died were younger than those who survived. Of the 23 people with complete medical details who died, 15 had hypertrophic cardiomyopathy. Most of the handful of survivors with complete medical records had ischaemic heart disease.

With one cardiac arrest per 184 000 runners and one sudden death per 259 000 runners, long distance races look less risky than collegiate athletics (one death per 43 770 participants per year), triathlons (one death per 52 630 participants), and jogging (one death per 7620 previously healthy middle aged joggers), say the authors. Male marathon runners have the highest risk, and it seems to be increasing, although firm conclusions are difficult from such limited numbers.

Invisible bursts of AF are implicated in some ischaemic strokes

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About a quarter of ischaemic strokes have no discernible cause, and doctors have long suspected that at least some of them are the result of undetected bursts of rapid atrial fibrillation. Supporting evidence emerged recently from a study of adults with a newly implanted pacemaker (n=2451) or implantable cardioverter defibrillator (n=129). The devices, acting as continuous heart monitors, showed asymptomatic and otherwise undetectable bursts of rapid atrial fibrillation in 261 of the 2580 participants. These participants were two and a half times more likely to have a stroke or systemic embolus than others, during 2.5 years of follow-up (1.69% v 0.69% per year; hazard ratio 2.49 (95% CI 1.28 to 4.85).

A linked editorial (p 178) says that, in this population at least, there seems to be a link between subclinical atrial fibrillation and ischaemic stroke. Whether one causes the other is still an open question, however, and we need an answer before we start prescribing warfarin. Trials are needed, but in the meantime doctors should use their clinical judgment along with the “venerable” CHADS2 score, which rates risk of stroke among people with atrial fibrillation. In this study, the absolute risk of ischaemic stroke peaked at 3.78% per year in adults with subclinical bursts of rapid atrial fibrillation and a CHADS2 score greater than 2 out of 6.

These adults were recruited for a randomised trial of continuous atrial pacing, which failed to prevent any kind of atrial tachyarrhythmia.

One or two embryos is enough for women having IVF

For the best chance of a live baby, women having in vitro fertilisation (IVF) need no more than two implanted embryos, say researchers. Increasing the number to three does not result in more live births for women of any age, it just increases the chance of complications, such as preterm birth and low birth weight. This new study challenges current recommendations by the UK Human Embryo and Fertilisation Authority, which allow transfer of three embryos for women over 40 years.

In an analysis of data collected by the authority between 2003 and 2007, transfer of two embryos was associated with significantly better odds of a live baby than transfer of one in women of all ages. Although the risk of twins, prematurity, and low birth weight also went up with transfer of an extra embryo, the absolute increase was less for older women than for younger ones. So women over 40 may have less to lose when deciding whether or not to implant a second embryo. But they have nothing to gain from three, say the authors.

Just over a quarter of the 124 148 IVF cycles analysed resulted in a live birth (27%, 95% CI 26.7% to 27.2%). The study confirmed that women over 40 are significantly less likely to deliver a live baby after a cycle of IVF than women under 40, however many embryos are transferred.

Memantine fails to prevent cognitive decline in adults with Down’s syndrome

General cognitive decline and clinical Alzheimer’s dementia are both common among older adults with Down’s syndrome, and Alzheimer-like pathology is almost universal from early middle age. Treatments are scarce, and memantine is the latest to disappoint researchers in a placebo controlled trial. The drug had no measurable impact on cognitive function, independence, behaviour, or any other outcome in adults with Down’s syndrome and a mean age of 51 years.

At the start of the trial, recruits had a mean score of just over 60 on a validated measure of cognitive function (DAMES) that runs from 0 to 220. A third (61/173, 35%) had a clinical diagnosis of Alzheimer’s disease. Memantine did nothing for this subgroup either. Participants took memantine or placebo for one year.

The trial ran out of money and was slightly underpowered, but it was still big enough and conclusive enough to direct research away from this treatment option, which clearly does not work for people with Down’s syndrome, says a linked comment (doi:10.1016/S0140-6736(11)61929-6). Memantine was a logical drug to try, because it works for other adults with moderate or severe Alzheimer’s disease and looked promising in preclinical studies in transgenic mice, but now we need to look elsewhere, it says. We also need to learn more about the neurobiology of Down’s syndrome, one of the most complex pathologies in humans.

Prevalence of obesity holds steady in the US

More than two thirds (68.8%, 95% CI 65.9% to 71.5%) of US men and women were overweight or obese in national surveys done during 2009 and 2010. More than a third (35.7%, 33.8% to 37.7%) were obese, with a body mass index of at least 30. The latest figures, although high, have not increased significantly since 2003, say researchers. The steady rise in the prevalence of obesity and overweight reported in previous decades might just be levelling off. But it shows no sign of falling.

The same surveys found that just under 17% (16.9%, 15.4% to 18.4%) of US children aged 2-19 were obese in 2009-10, and about a third (31.8%, 29.8% to 33.7%) were either overweight or obese. Just under 10% (9.7%, 7.6% to 12.3%) of infants and toddlers were above the 95th centile on growth charts tracking normal weight for length. Trends in childhood obesity suggest little change since 1999 in girls, and a slight but significant increase in boys, which seemed to level off between the last two surveys (2007-8 and 2009-10).

The latest survey weighed and measured 4111 children and adolescents, in addition to 5926 adult men and women. Both samples were selected to represent the general civilian population of the US, excluding those living in institutions and pregnant women.

Neonatal caffeine treatment improves motor function at 5 years, but not survival

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The respiratory stimulant caffeine helps prevent apnoea in premature babies and improves the chance of survival to 18 months without a severe disability. But the survival advantage disappears by the age of 5 years, according to an extended follow-up of 1640 very premature babies recruited for a landmark placebo controlled trial between 1999 and 2004. Rates of death or severe impairment were lower among 5 year old children who had been treated with caffeine, but the difference was not significant (21.1% v 24.8%; adjusted odds ratio 0.82, 95% CI 0.65 to 1.03).

None of the components of the primary outcome was significantly less common in children treated with caffeine, including severe motor impairment, learning disability, behavioural problems, poor general health, blindness, or deafness. But a more detailed analysis of motor function found that children treated with caffeine had better gross motor function (higher scores) and better manual dexterity at 5 years than placebo controls. Both these benefits are worth having, says a linked editorial (p 304). Motor function at this age has important implications for adult life.

Perhaps the most striking result was a general improvement in cognitive ability between the ages of 18 months and 5 years. On average, children scoring 70 on an IQ test at 18 months scored 20 points higher at 5 years. All children weighed between 500 g and 1250 g at birth.

Expected rates of in-hospital VTE after joint replacement surgery

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One in 100 adults having knee replacement surgery (1.09%, 95% CI, 0.85% to 1.33%) and one in 200 having hip replacement surgery (0.53%, 0.35% to 0.70%) develops symptomatic venous thromboembolism (VTE) before leaving hospital, even when given recommended prophylaxis. A meta-analysis of 41 trials and six observational studies reported VTE rates before discharge among adults given prophylactic low molecular weight heparin, a subcutaneous factor Xa inhibitor, or an oral direct inhibitor of factors Xa or IIa.

The authors hope their figures will be a useful benchmark to help rate hospitals for quality of care and patient safety. A worthy goal, says an editorial (p 306), but it may be a little harsh to judge hospitals treating all comers against benchmarks derived from tightly run and selective randomised trials. And it may be misleading to focus on thromboembolism that occurs before discharge. Patients go home a few days after joint replacement surgery and remain at risk for weeks. The incidence of VTE over three months would be a better measure of quality and safety, says the editorial. But first we need a simple system for tracking and recording events after patients go home. Electronic patient records could eventually fulfil this role.

Notes

Cite this as: BMJ 2012;344:e401

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