1 Epidemiological Research Unit, Institut National de la Santé et, de la Recherche Médical, U169, 16, avenue PV Couturier, F-94807 Villejuif Cédex, France
To the Editor.
From a study conducted on 415 asthmatic children aged 1 to 17 years, Murray and Morrison1 observed a greater effect of passive smoking on lung function in boys than in girls and in older than in younger children. They interpret their findings by the cumulative effect of maternal smoking and the known susceptibility of boys to asthma. Different growth patterns between boys and girls may be an additional hypothesis to explain their observations.