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Parents should remove risk factors to reduce asthma in children

BMJ 2001; 322 doi: https://doi.org/10.1136/bmj.322.7287.637 (Published 17 March 2001) Cite this as: BMJ 2001;322:637
  1. David Spurgeon
  1. Quebec

    More than half a million American children aged under 6 years with asthma would not have the disease if risk factors such as tobacco smoke and pets were removed from their homes, a new study published in the current issue of Pediatrics has found (2001;107:505-11).

    Dr Bruce Lanphear, associate professor of paediatrics at the Children's Hospital Medical Center of Cincinnati and lead author of the study, said: “If residential exposures, including tobacco smoke and indoor allergens, were eliminated, and if these exposures are determined to cause asthma—which is the central hypothesis among experts—we would reduce asthma in this age group by 39%, or about 530 000 cases a year. This could have a profound effect on medical costs in the United States and, more importantly, on the health of children.”

    The study showed that the annual cost of asthma as a result of these exposures is more than $402m (£270m) annually. Asthma, the most common chronic illness of childhood, is estimated to affect more than four million children in the United States, and from 1980 to1993 its prevalence increased by 75%, primarily in children aged under 5. Each year the condition leads to more than three million clinic visits, 550 000 visits to emergency departments, 150 000 admissions to hospital, and more than 150 deaths in children aged under 15 years.

    Risk factors in the home identified by researchers include allergies to pets, tobacco smoke, use of a gas stove, and having a dog in the house. Paradoxically, a study published in the current issue of the Lancet (2001;357:752-6) shows that in some cases, having a cat can prevent a child becoming asthmatic by producing tolerance to the allergens.

    Because risk factors vary by such things as geography, scale of urbanisation, and poverty, the overall contribution of housing factors to asthma in children has been unclear.

    The study reported in Pediatrics involved 8257 children younger than 6 who participated in the third national health and nutrition examination survey (NHANES III) between 1988 and 1994: 5.9% of them had asthma that had been diagnosed by a doctor. This extrapolates to 1.36 million children aged under 6 with asthma in the United States.

    “Children who had a history of allergies to a pet were 24 times more likely to have doctor-diagnosed asthma,” said Dr Lanphear. “More than 350 000 cases of childhood asthma were attributable to having a pet allergy. Parents need to consider carefully the risks and benefits of owning a pet, particularly during early childhood and especially if there is a maternal history of an allergic condition.”

    Environmental exposure to tobacco smoke accounted for 177 000 excess cases; having a dog in the house accounted for 140 000 excess cases; and using a gas hob or oven for 59 000 excess cases, Dr. Lanphear says.

    Exposures in the home account for more excess cases than having a parent with a history of atopy. “Taken together, these and other data demonstrate that children's health is inextricably linked with housing,” he said “Unfortunately, despite growing evidence that residential exposures have a dramatic impact on children's health, housing is largely ignored as a public health problem.”