American researchers have confirmed earlier findings of how inhaling cigarette smoke can aggravate a child's asthma.

Most previous studies in this area have relied on parents reporting when their children have been exposed to smoke, and so may not have been a reflection of the actual smoke inhaled. However, in this study of 199 children, tobacco exposure was determined by measuring the level of cotinine a metabolic derivative of nicotine in the child's urine.

Researchers found that the average level of cotinine in the urine of the 116 children not exposed to smoke was 5.6ng per milliliter; in the 53 exposed to smoking by the mother or other people, it was 13.1ng per milliter; and 55.8ng per millileter in the 30 children exposed to smoke from their mother and others.

Higher levels of cotinine and higher levels of exposure to smoking was associated with increase in "acute exacerbations" or asthma and reductions in respiratory function. New Eng J Med, 10 June 1993.

Still on asthma, drug company Glaxo may have wildly underestimated the number of deaths of sufferers using its bronchodilator salmeterol, according to the Drug Safety Research Unit in Southampton. Glaxo looked at 16,787 patients treated with salmeterol over 16 weeks and found there were 54 deaths from all causes, of which 12 were from asthma.

If Glaxo's findings were representative, a total of 150 deaths would be expected over the course of a year, with 30 to 40 resulting from asthma. However, the research unit is currently conducting its own longer study, the preliminary results of which after a year "differ remarkably" from Glaxo's.

In this study, 17,000 patients were followed up for more than a year, of which 1006 have died. So far, 572 of these deaths have been followed up, out of which 84 have already been identified as being caused by asthma. On this basis, the unit reckons that by the end of its analysis, 150 will have died from asthma, of which around 50 would have occurred during the first 16 weeks the same period when Glaxo identified just 12 deaths. William Inman of the Drug Safety Research Unit says: "We may thus record an overall death rate about six times and a death rate from asthma about four times the rates reported by [Glaxo]." It would be unwise to use the results of the Glaxo study to estimate the mortality from asthma, he adds.