Primecuts – This Week In The Journals

February 28, 2011

By Jason Feliberti, MD

Faculty Peer Reviewed

In World news, as the unrest in the Middle East and North Africa continues, increased uncertainty of crude oil production in the region has led to a volatile market for crude oil [1]. With pricing currently at $97.88 a barrel, and climbing, the rising costs of crude oil may threaten the U.S. economic recovery; from decreased consumer spending, to decreased rates of hiring [2].  Natural gas has been proposed as a “cleaner” and more globally distributed fuel (of which the U.S. has a plentiful supply) that may decrease our dependence on foreign oil [3].

The possible decrease in air pollution with natural gas brings me to my first article: published in the Lancet, a meta-analysis of 36 epidemiologic studies, Nawrot, et. al, identified air pollution as an important trigger of non-fatal myocardial infarction [4]. From the 36 epidemiologic studies, 13 types of triggers of acute MI were identified with the highest OR ascribed to cocaine use (OR 23.7; 95% CI, 8.1-66.3).  Air pollution at 10 ug/m3 reduction had an OR of 1.02 (95% CI, 1.01-1.02), and Air pollution at 30 ug/m3 reduction had an OR of 1.05 (95% CI, 1.03-1.07).  Moreover, Traffic exposure had an OR of 2.92 (95% CI, 2.22-3.83). However, taking into account the OR and prevalence of exposure, the calculated Population attributable risk (PAF) was highest for traffic exposure (7.4%; 95% CI, 4.81-10.49), with Air pollution 10ug/m3 reduction PAF of 1.57% (95% CI, 0.89-2.15), and Air pollution 30ug/m3 reduction PAF of 4.76% (95% CI, 2.63-6.28); implying that if Particulate matter of 10 μm or less in aerodynamic diameter (PM10) were decreased by 30ug/m3, 4.8% of acute MI might be avoided or delayed.  While the prevalence of air pollution was assumed to be 100% (as people cannot avoid air pollution exposure), and exposure to traffic which was 4.1%, it remains uncertain if increased exposure to air pollutants while sitting in traffic (or increased stress, or a combination thereof) can explain the high PAF for traffic exposure and acute MI.  Perhaps a combination pill of aspirin and Xanax is needed for those with a rather traffic laden commute; probably not, but decreasing the level of air pollutants in major urban cities to the WHO target of 20 ug/m3 would be beneficial for public health.

Speaking of exposures, as it turns out the exposure to radiofrequency-modulated electromagnetic fields (RF-EMFs) via your cell phone may be making changes to your brain’s activity [5]. In a preliminary communication published in JAMA, Volkow, et. al, has shown that in healthy participants a 50-minute cell phone exposure was associated with an increase in brain glucose metabolism in the region closest to the antenna [6].  This randomized crossover study measured brain glucose metabolism, via PET scanning, of 47 healthy subjects with cell phones placed on the right and left ears: once with the right cell phone on for 50-minutes (but muted, to avoid CN VIII stimulation), and once with both phones off.  Metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for the on then off conditions (35.7 vs 33.3 umol/100g per minute; mean difference, 2.4 [95% CI, 0.67-4.2]; P=.004).  Studies regarding the concern that RF-EMFs emitted by cell phones may induce brain cancer remain inconclusive. While the clinical significance of this study remains unknown, it does show that the human brain is sensitive to acute exposure to RF-EMFs via cell phones. Further studies are needed to assess if these effects have long-term harmful sequella.

So, air pollution bad, traffic worse, cell phones questionable… how about environmental microorganisms? Well, according to Ege, et. al childhood exposure to a wide range of microbes (ie., children living on farms) have a decreased risk of developing asthma [7].  Score one for the Hygiene hypothesis (or rather the dirty is better hypothesis)! As published in the NEJM, in two cross-sectional studies (PARSIFAL [Prevention of Allergy – Risk Factors for sensitization in children related to Farming and Anthroposophic lifestyle] and GABRIEL [Multidisciplinary study to identify the genetic and environmental causes of asthma in the European community]) children living on farms in central Europe and the microbiologic diversity of their surroundings were compared to respective reference groups. It was found that diversity of microbial exposure was inversely related to the risk of asthma (OR for PARSIFAL, 0.62; 95% CI, 0.44-0.89; OR for GABRIELA, 0.86; 95% CI, 0.75-0.99). Moreover, exposure to certain families of species of microbial flora (fungal taxon eurotium, listeria monocytogenes, bacillus species, corynebacterium, and others) showed an inverse relationship between exposure and the development of asthma. While this study did not identify specific microbes that confer protection, it does provide an explanation for the protective effect of farming environments on children from developing asthma. Now where can I buy a cow…

To round out this week’s Primecuts I would like to mention two studies, one of the brain, and one of the heart. First, in the Lancet, Sanset, et. al, investigated whether careful blood-pressure (BP) lowering treatment with an angiotensin-receptor blocker (ARB), candesartan, is beneficial in patients with acute stroke and elevated BP [8]. In this randomized, placebo-controlled, double-blind trial, patients from 146 centers in nine north European countries, who had an acute stroke (ischemic or hemorrhagic) and an elevated BP (systolic BP 140 mmHg or higher) were randomized to candesartan or placebo for 7 days.  During the 7 day treatment BP in the candesartan group was significantly lower (147/82 mm Hg [SD 23/14] vs 152/84 mm Hg [SD 22/14; p <0.0001). However, during the 6 months of follow-up the risk of the composite vascular endpoint (death, MI, or stroke within 6 months) did not differ between the two groups (Candesartan vs. placebo: 120 events vs. 111 events; adjusted hazard ratio 1.09, 95% CI 0.84-1.41; p=0.52). Moreover, analysis of the functional outcome (as assessed by the modified Rankin Scale at 6 months) suggested a higher risk of poor outcome in the candesartan group (adjusted common odds ration 1.17, 95% CI 1.00-1.38; p=0.048 [not significant at p<0.025 level]).  Ongoing trials will clarify if this finding is generalisable or if subgroups will benefit from BP lowering in the setting of acute stroke; however, it was the feeling of the authors that until these trials were completed there appears to be no indication for the routine BP lowering in the acute phase of stroke.

Finally, as published in Science, Porrello et. al, showed that a mammalian heart has the ability to regenerate lost tissue [9]. In this study hearts of 1-day-old neonatal mice can regenerate after partial surgical resection of the apex of the heart, but that capacity was lost after 7 days of age. Genetic fate mapping showed that the regenerated cardiomyocytes were from preexisting cardiomyocytes, and echocardiography performed 2 months after surgery revealed that the regenerated ventricular apex had normal systolic function.  Oh to be young at heart… That’s it for this week’s Primecuts.

Dr. Feliberti is a 1st year resident at NYU Langone Medical Center

Peer reviewed by Cara Litvin, section editor, Clinical Correlations

Image courtesy of Wikimedia Commons

References:

1.  Hauser, Christine. “Wall Street Wanders as oil prices ease.” New York Times. February 24, 2011. http://www.nytimes.com/2011/02/25/business/global/25markets.html?ref=oilpetroleumandgasoline

2.  Indiviglio Daniel. “10 ways rising oil prices endanger the U.S. Recovery” The Atlantic. February 23, 2011. http://www.theatlantic.com/business/archive/2011/02/10-ways-rising-oil-prices-endanger-the-us-recovery/71604/

3.  Gardiner, Beth. “Is Natural Gas Good, or Just Less Bad?” New York Times. February 22, 2011. http://www.nytimes.com/2011/02/21/business/energy-environment/21iht-renogas21.html?scp=6&sq=gas&st=cse

4.  Nawrot TS, Perez L, Kunzli N, Munters E, Nemery B. Public health importance of triggers of myocardial infarction: a comparative risk assessment. The Lancet. 2011; 377(9767):732-740. http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)62296-9/abstract

5.  Parker-Pope, Tara. “Cellphone use tied to changes in Brain Activity” New York Times. February 22, 2011. http://well.blogs.nytimes.com/2011/02/22/cellphone-use-tied-to-changes-in-brain-activity/?ref=health

6.  Volkow ND, Tomasi D, Wang GJ, Vaska P, Fowler JS, Telang F, Alexoff D, Logan J, Wong C. Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism. JAMA. 2011 Feb 23;305(8):808-13. http://jama.ama-assn.org/content/305/8/808.abstract

7.  Ege MJ, Mayer M, Normand AC, Genuneit J, Cookson WO, Braun-Fahrländer C, Heederik D, Piarroux R, von Mutius E; GABRIELA Transregio 22 Study Group. Exposure to environmental microorganisms and childhood asthma. N Engl J Med. 2011 Feb 24;364(8):701-9. http://www.nejm.org/doi/full/10.1056/NEJMoa1007302

8.  Sandset EC, Bath PMW, et. al. The angiotensin-receptor blocker candesartan for treatment of acute stroke (SCAST): a randomized, placebo-controlled, double-blind trial. 2011; 377(9767):741-750. http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(11)60104-9/abstract

9.  Porrello ER, Mahmoud AI, et. al. Transient Regenerative Potential of the Neonatal Mouse Heart. Science 2011;331(6020)1078-1080. http://www.sciencemag.org/content/331/6020/1078.abstract

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