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27-06-2012 | Article

Global medical news in review: June 10-16, 2012

MedWire News: A roundup of select stories of interest to US physicians from the Merck Medicus Global Medical News wire.

Urban allergies

Children living in urban centers are more than twice as likely to have peanut and shellfish allergies as those living in rural communities, US study data show.

Ruchi Gupta (Northwestern University Feinberg School of Medicine, Chicago, Illinois) and team collected survey data on the prevalence of food allergies (peanut, shellfish, milk, fin fish, egg, tree nut, wheat, and soy) for 38,465 children under 18 years of age who were living in the USA during 2009 to 2010.

Geographic areas were classified as urban centers (most urbanized), metropolitan cities, urban outskirts, suburban areas, small towns, and rural areas (most rural) using Rural-Urban Commuting Area Codes.

Overall prevalence of food allergy increased significantly with increasing population density, from 6.2% in rural areas to 9.8% in urban centers, report the researchers. Prevalence rates for specific allergens also varied significantly by urban/rural status. Specifically, peanut allergies were twice as prevalent in urban centers as in rural areas (2.8 vs 1.3%), while shellfish allergies were more than twice as common in urban as in rural areas (2.4 vs 0.8%).

Only milk and soy allergy appeared to affect a similar proportion of children regardless of geographic area, they report in Clinical Pediatrics.

Allergies were significantly more common at southern and middle latitudes compared with northern latitudes, but after accounting for this, along with race/ethnicity, gender, and age, living in an urban center was still associated with a greater probability of having a food allergy than was living in a rural area (odds ratio=1.7).

Go easy on the CT in kids

The use of computed tomography (CT) scans should be minimized in children, recommend researchers who found a significantly increased risk for malignancy with repeated imaging.

Over 10 years, one excess case of leukemia and brain tumor each will occur per 10,000 head CT scans performed in patients aged less than 10 years, estimate Mark Pearce (Newcastle University, UK) and colleagues, reporting their research in The Lancet.

"Although clinical benefits should outweigh the small absolute risks, radiation doses from CT scans ought to be kept as low as possible and alternative procedures, which do not involve ionising radiation, should be considered if appropriate," they write.

The team collated cancer incidence and mortality data for patients aged under 22 years who underwent CT imaging in National Health Service centers in England, Wales, and Scotland between 1985 and 2002.

The patients included in the study had no previous history of malignancy. To avoid inclusion of CT scans related to cancer diagnosis, patients were followed up for leukemia and brain tumors 2 and 5 years after initial imaging, respectively, the team explains.

Overall, 74 of 178,604 patients (283,919 scans) were diagnosed with leukemia, and 135 of 176,587 patients (279,824 scans) were diagnosed with a brain tumor.

The researchers calculated mean dose to the red bone marrow and brain tissue, and discovered a significant and positive correlation between CT scan radiation dose and the risk for leukemia and brain tumors, with excessive relative risks (RRs) of 0.036 and 0.023, respectively.

When compared with patients with a cumulative radiation dose of less than 5 mGy, the RR for leukemia for patients with a cumulative dose of 30 mGy or above (average dose 51 mGy) was 3.18. For patients with a cumulative dose of 50-74 mGy (average dose 60 mGy), the RR for brain tumor was 2.82.

Little sleep, high blood pressure

Individuals who sleep for 5 hours or less each night are at increased risk for developing hypertension, suggest study findings.

Damien Leger (Paris Descartes University, France) and colleagues measured blood pressure (BP), took blood samples, and administered standardized health and sleep questionnaires to 1046 French adults, aged on average 55.5 years, who visited general practitioners at primary care centers in Paris.

The researchers report that 42.0% of individuals were diagnosed as having hypertension (defined as having either a systolic BP [SBP] of 140 mmHg or more or diastolic BP [DBP] of 90 mmHg or more, or by the use of antihypertensive medications) with 34.5% on antihypertensive medication, 28.5% with elevated SBP and DBP, 32.9% with elevated SBP alone, and 4.1% with only elevated DBP.

When the researchers analyzed BP according to sleep category duration among patients not taking antihypertensive medications, they found significant differences in DBP between certain groups. Those who slept 5 hours or less per night had a higher DBP, at 82.2 mmHg, than those who slept 6 hours, 7 hours, or 9 or more hours per night, with DBPs of 78.6, 80.2, and 78.6 mmHg, respectively. No significant differences were seen for SBP among the groups.

The prevalence of hypertension increased significantly in line with decreasing sleep hours, from 32.9% for those sleeping 9 hours or more to 51.0% for those sleeping 5 hours or less per night, they write in TheJournal of Hypertension.

Liters a day keep the nephrologist away

A healthcare system-wide analysis suggests that millions of dollars spent annually on nephrolithiasis could be saved if more people drank more than 2 liters of water daily, report Yair Lotan (University of Texas Southwestern Medical Center, Dallas, Texas) and colleagues.

As reported in The British Journal of Urology International, the researchers conducted a healthcare system-wide analysis to estimate the cost-effectiveness of high-water intake (>2 L/day) versus low-water intake (<2 L/day).

The researchers estimated the annual incidence of nephrolithiasis in the general population to be 0.003% and assumed a 40% reduction in risk for stones with the increased water intake. The incidence of stones was based on estimates from France where there are approximately 21,000 cases among a population of 65 million people.

The total cost of nephrolithiasis was $5345 in the base-case analysis, with direct costs of$ 3467 that include the cost of treatment and complications.

Based on the population of France, the annual budget cost was $739 million for the payer. For one patient treated for 25 years, increasing water intake can save the payer an average of$ 38 per person.

Increasing water intake 100% in the entire population would result in a cost saving of \$ 342 million and 9265 fewer stones.

To avoid cancer risk, try not to breathe

Diesel exhaust fumes have been classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC), following a week-long meeting of international experts.

The group concluded that there is "sufficient evidence" (group 1) to show that exposure to diesel engine exhaust is associated with an increased risk for lung cancer.

In 1988, the IARC, which is part of the World Health Organization, classified diesel exhaust as "probably carcinogenic to humans." There has since been mounting concern about its cancer-causing potential. This was highlighted in a recent study by the US National Cancer Institute/National Institute for Occupational Safety and Health, as reported by MedWire News, which showed an increased risk for death from lung cancer among underground miners exposed to diesel exhaust.

The Working Group reviewed the scientific evidence for a link between diesel exhaust and cancer. In addition to finding sufficient evidence that diesel exhaust causes lung cancer, the group also found more limited evidence of a link with an increased risk for bladder cancer.

In addition, the Working Group concluded that gasoline exhaust was "possibly carcinogenic to humans" (Group 2B), a finding that is unchanged from the previous evaluation in 1989.

The rhythm of life in atrial fibrillation

Rhythm control therapy for atrial fibrillation (AF) may improve survival rates compared with rate control therapy when used long term, show study results published in Archives of Internal Medicine.

While patients treated with either type of drug had similar mortality rates within 4 years of treatment initiation, by 8 years, the mortality rate had dropped by almost a quarter among rhythm versus rate control-treated patients, say the researchers.

The reduction in risk for death was even more pronounced in patients who had maintained the treatment to which they were initially assigned. This indicates that "the use of rhythm control therapy may be beneficial for patients with AF in whom antiarrhythmic drugs are effective and well tolerated," write Louise Pilote (Royal Victoria Hospital in Montreal, Quebec, Canada) and co-authors.

Their study included 26,130 Canadian patients aged at least 66 years old who were newly diagnosed with AF during hospitalization between 1999 and 2007. All initiated treatment within 7 days of discharge.

A total of 24.5% initiated rhythm control treatment, with amiodarone (51.0%) and sotalol (24.0%) the most common prescriptions. Beta-blockers (56.0%), digoxin (40.0%), and/or calcium-channel blockers (30%) were the most common rate-control drugs prescribed.

After a short-term increase in mortality among rhythm control-treated patients, mortality rates were comparable between groups for the first 3 years after treatment initiation.

By contrast, after 5 years posttreatment, Pilote and colleagues found a steady decrease in mortality among rhythm relative to rate control-treated patients.

By Neil Osterweil