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BMJ 2009; 338 doi: http://dx.doi.org/10.1136/bmj.a3189 (Published 07 January 2009) Cite this as: BMJ 2009;338:a3189

Sleep saves coronary arteries

Recent studies have linked the duration of sleep to several risk factors for coronary artery calcification (the accumulation of calcified plaques that has been shown to predict coronary events), including sex, age, education, body mass index, blood pressure, and regulation of glucose.

Now a population based cohort study of 495 healthy participants aged 35-47 years at baseline found that longer sleep, as measured by wrist actigraphy, is also directly associated with lessened calcification of coronary arteries five years later, independent of various potential confounders (age, sex, race, education, risk for apnoea, and smoking status) and mediators (lipids, blood pressure, body mass index, diabetes, inflammatory markers, alcohol consumption, depression, hostility, and self reported medical conditions). However, other measures of duration and quality of sleep, including self reports and fragmentation index, failed to show significant associations with incident coronary calcification.

At five years, 12% of participants had new coronary calcification detected by computed tomography. Sleeping one hour longer each night reduced the odds of being in this group by about a third, and this was modelled as equivalent in effect to a decrease in systolic blood pressure of 16.5 mm Hg. The authors stress that the finding needs further testing in future studies, which should also shed light on a possible association with coronary events and disentangle the role of mediators.

How birth weight affects risk for type 2 diabetes

We know that low birth weight is associated with an increased risk for type 2 diabetes in adulthood. Now a systematic review based on 30 studies in 31 populations and 6090 people with diabetes out of 152 084 participants examines the strength, consistency, dependency, and shape of the association.

The review confirmed that in most populations birth weight was inversely related to the risk of type 2 diabetes. The combined odds ratio based on all 31 populations was 0.80 (95% CI 0.72 to 0.89) per km of birth weight. Contrary to previous reports, the review did not find evidence that the association between birth weight and risk of type 2 diabetes is dependent on adult body size or confounded by adult socioeconomic status. Also, this report could not confirm previous conclusions that the association is U shaped.

The positive association found in two native North American populations, with a high prevalence of diabetes and obesity, and one young Canadian population of white European origin could mean that the association between birth weight and type 2 diabetes is becoming increasingly positive in younger generations. Thus high, rather than low, birth weight could become an increasingly important risk factor for diabetes in the future.

Of note, none of the included studies adjusted for smoking in pregnancy—a possible confounder that is associated with lower birth weight and the offspring’s risk of smoking in adulthood, which in turn increases the risk of diabetes.

Machine perfusion is better than static cold for storing kidneys

Static cold storage and hypothermic machine perfusion are commonly used for storing kidneys from dead donors before transplantation, but until now it hasn’t been clear which method is best. An international trial randomly assigned kidneys from 336 dead donors to either method of storage and followed up the 672 recipients for one year.

People who received kidneys that had been stored using hypothermic machine perfusion had half the risk of delayed graft function (necessitating dialysis in the first week after transplantation) compared with those who received kidneys preserved by static cold storage (89 (26.5%) v 70 (20.8%) recipients, adjusted odds ratio 0.57, P=0.01). The machine perfusion method also improved several other outcomes—duration of delayed graft function, rate of decrease in the recipient’s serum creatinine, and survival of the graft at one year (94% v 90%, P=0.04). A subgroup analysis of kidneys donated after cardiocirculatory death, which is becoming more common in many countries, showed that recipients of such kidneys also had better graft function after machine perfusion.

Machine perfusion requires the use of a device that constantly pumps a solution through kidney blood vessels at a temperature between 1°C and 10°C. Static cold storage—a simpler procedure where the kidney is flushed, cooled with a preservation solution, and transported on ice—is currently used in four out of five kidney transplants in the US, and almost all procedures in the Eurotransplant countries.

Selective decontamination can save lives in intensive care

Selective digestive tract decontamination (four days of intravenous cefotaxime combined with topical tobramycin, colistin, and amphotericin B in the oropharynx and stomach) and selective oropharyngeal decontamination (oropharyngeal application of the same antibiotics without systemic treatment) are used in intensive care units to prevent infection in some patients, but to what effect?

A trial in 13 intensive care units looked at 5939 patients who at recruitment were expected to be intubated for at least two days or to remain in intensive care for at least three days. The primary outcome—mortality at 28 days—for standard care, selective oropharyngeal decontamination, and selective digestive tract decontamination was 27.5%, 26.6%, and 26.9%, respectively. Both decontamination regimens reduced mortality relative to standard care (adjusted odds ratio 0.86, 95% CI 0.74 to 0.99 for oropharyngeal decontamination; 0.83, 0.72 to 0.97 for digestive tract decontamination). Both interventions also improved microbiological outcomes, such as carriage of Gram negative bacteria in the respiratory and intestinal tracts.

The authors suggest that, given the importance of antibiotic resistance in intensive care units, oropharyngeal decontamination may be preferable to digestive tract decontamination because although its effect on survival is similar it doesn’t include systemic prophylaxis and uses fewer topical antibiotics. In settings with high antimicrobial resistance, the best option might be oropharyngeal decontamination combined with an antiseptic agent, such as chlorhexidine.

Notes

Cite this as: BMJ 2009;338:a3189