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New study adds to growing evidence of early smoke exposure and infection

Researchers from Hong Kong found that children who are exposed to secondhand tobacco smoke are at greater risk of being hospitalised for infections than those brought up in a smoke-free environment.

Dr. M. K. Kwok of the University of Hong Kong and colleagues found that the risk of being hospitalised was greatest among babies 6 months old and younger, but the increased risk persisted up until the children were 8 years old. The findings suggest that secondhand smoke exposure may not only be harmful to children's respiratory tracts, but to their immune systems as well, Kwok and colleagues say.

While the danger smoke exposure poses to children's developing respiratory systems is well understood, less is known about its effects on overall infection risks.

To investigate, the researchers looked at a group of 7,402 children born in 1997 who were followed up until age 8. At the study's outset, nearly 42% were exposed to secondhand smoke at home.

Children who had been within 3 meters (or about 9.8 feet) of a person smoking cigarettes at any point during their first 18 months of life were 14% more likely to be hospitalised for any type of infection by 8 years of age, the researchers found.

The greatest difference was seen among infants, with 1 in 3 exposed babies being hospitalised for an infection by the time they were one year old. Exposure during the first 3 months of life had the strongest effect.

Premature and low birth weight infants were more vulnerable to the effects of secondhand smoke; they were twice as likely to be hospitalised for an infection by age 8 than unexposed children.

The researchers conclude that "What this study adds is evidence of a window of greater vulnerability to secondhand smoke exposure in early infancy, which extends to all infectious illnesses not just respiratory and related infections, and which may have a larger and more long-lasting impact in developmentally more vulnerable subgroups, such as premature or low birth weight infants."

Source: Reuters News, 4th June 2008
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