Genes influence risk from second-hand smoke

Children harboring a particular variant in the TNF gene who are exposed to second-hand smoke are at increased risk of frequent respiratory-related absences from school, researchers at the University of Southern California, Los Angeles, report.

In a study of more than 1,300 fourth graders, Dr. Frank D. Gilliland and colleagues found the effect of passive smoke exposure on illness differed according to TNF genotype.

Children carrying at least one copy of the so-called “TNF-308 A variant” who were exposed to two or more smokers in the household had a two-fold increased risk of respiratory illness causing school absence, compared with children with the more common “TNF GG genotype” who were not exposed to second-hand smoke.

The risk of lower respiratory tract illness causing school absence was four-fold higher in carriers of another TNF variant known as “TNFG-308 A variant” who were exposed to second-hand smoke.

The researchers point out in the American Journal of Respiratory and Critical Care Medicine that past studies have shown that the TNF-308 variant may alter the expression of genes and boost the intensity of the inflammatory response to second-hand smoke, “leading to increased risk and severity of respiratory illness in susceptible groups.” More studies are needed to confirm this.

SOURCE: American Journal of Respiratory and Critical Care Medicine, December 2005.

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