Secondhand smoke raises risk of heart disease
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Exposure to secondhand smoke greatly increases the risk of heart attack and stroke, UK investigators report in the journal Circulation.
Dr. Andrea Venn and Dr. John Britton, both from the University of Nottingham, analyzed data from the Third National Health and Nutrition Examination Survey, conducted between 1988 and 1994. Exposure to smoke was estimated based on blood levels of cotinine, a biological marker for nicotine. The researchers used blood levels of a clotting protein called fibrinogen and homocysteine, an amino acid, as a rough indicator of the risk of heart attack and stroke.
Their analysis included 7,599 subjects who had never smoked. Cotinine was undetectable in 1,371 subjects, 3,115 subjects had low cotinine levels, and 3,113 subjects had high levels.
The average fibrinogen and homocysteine levels were significantly higher in subjects with detectable levels of cotinine than those with undetectable levels. There was little difference in fibrinogen and homocysteine levels between subjects with low cotinine and those with high cotinine levels.
The investigators note that even though cotinine levels as a result of secondhand smoke exposure were only about 0.1 percent of those seen in active smokers, the increased levels of fibrinogen and homocysteine were equivalent to about 30 percent to 45 percent of the levels seen in active smokers.
These results suggest that even very low levels of exposure to tobacco smoke can be associated with an increased risk of heart attack and stroke, the authors conclude.
SOURCE: Circulation, February 27, 2007.
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