ScienceDaily (May 28, 2008) — Children exposed to second hand tobacco smoke are more likely to get severe infectious diseases and have to be admitted to hospital, finds research published online ahead of print in Tobacco Control.

These children are at greater risk of a whole range of infectious illnesses, such as meningococcal disease, and not just respiratory illness, the results showed. Exposure to smoke in the first few months of life did the most harm, especially if they had a low birth weight or had been born prematurely.

The researchers assessed the relationship between second hand smoke exposure and first admission to hospital for any infectious illness for 7,402 children born in Hong Kong in April and May 1997. The children were followed until they were eight.

Children who lived in the household of someone who smoked within three metres of them during their first few months of life were the most at risk of being admitted to hospital with one in three admitted by the age of 12 months.

The earlier the exposure to smoke the more profound the effect with exposure to second hand smoke during the first six months of life increasing the likelihood of being admitted to hospital for an infectious disease during the eight years by almost 45 per cent.

More vulnerable infants were also at increased risk of hospitalisation with those born with a low birth weight being 75 per cent more likely to be admitted to hospital with an infectious disease during the eight years and those who were premature being twice as likely.

The authors suggest that second hand smoke might affect the immune as well as the respiratory system of young children. “An excess risk of severe morbidity from both respiratory and other infections for all infants exposed to second hand smoke suggests that such exposure, as well as acting via direct contact with the respiratory tract, may also affect the immune system,” they say.

They add that premature infants and those with a low birth rate might be more at risk because their respiratory and immune systems were less well developed.

Journal reference:

1. Kwok, Man-Ki, Schooling, C Mary, Ho, Lai-Ming, Leung, SL, Mak, Kwok-Hang, McGhee, Sarah M, Lam, Tai-Hing, Leung, Gabriel M. Early life second hand smoke exposure and serious infectious morbidity during the first eight years: evidence from Hong Kong's "Children of 1997" birth cohort. Tob Control, Published Online First: 27 May 2008 DOI: 10.1136/tc.2007.023887

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