Secondhand smoke raises heart disease risk: study
DALLAS (Reuters) - Warning signs for cardiovascular disease are higher in people exposed to secondhand tobacco smoke, adding to the link between "passive smoke" and heart disease, according to a study released on Monday.
"Our study provides further evidence to suggest low-level exposure to secondhand smoke has a clinically important effect on susceptibility to cardiovascular disease," said Dr. Andrea Venn of University of Nottingham in Britain, lead author of the study.
"This is the first ... study to relate the levels of these markers to an objective measure of secondhand smoke exposure, rather than self-reported exposure," said Venn, an associate professor of epidemiology and public health.
The study, published this week in "Circulation: Journal of the American Heart Association," measured the level of cotinine in the blood of participants.
Cotinine is a major indicator of nicotine intake and hence exposure to tobacco smoke, according to the American Heart Association (AHA).
The researchers also checked if people exposed to secondhand smoke at home, work or other places had higher levels of fibrinogen, homocysteine and C-reactive protein -- all markers or indicators of cardiovascular disease.
It examined records from America's third National Health And Nutrition Examination Survey (NHANES III, 1988-94), which included 7,599 adults who had never smoked.
Eighteen percent of those surveyed from this group had no detectable levels of cotinine while the remainder had high or low levels.
Eighteen percent of those with low levels and 56 percent with high levels said they had lived with a smoker at home or had been exposed to secondhand smoke at work.
"Researchers found the low- and high-cotinine groups had significantly higher levels of fibrinogen and homocysteine (with fibrinogen levels estimated at 9-10 milligrams per deciliter higher and homocysteine levels at 0.8 micromoles per liter higher) than the 'no detectable' group," the AHA said.
The raised levels of fibrinogen and homocysteine translate into a 5 percent increased disease risk though studies elsewhere have suggested that other factors can raise the disease risk from secondhand smoke by up to 30 percent.
Fibrinogen is a protein and homocysteine an amino acid in the blood. Both are markers of inflammation and are also involved in blood clotting.
"Even when participants weren't exposed to smoke at the workplace or at home, many had low or high levels of cotinine in their blood," Venn said.
"These people may be exposed in bars or restaurants or perhaps in other people's homes such as those of relatives or friends. This suggests that even people exposed to low levels of secondhand smoke may be at increased risk."
