Assessment Of Passive Exposure To Tobacco Smoke In Wheezing Infants By Urinary Cotinine

To describe the frequency of passive smoking among infants and respiratory symptoms, using a standardized questionnaire and cotinine dosage in a urine sample. A population-based cross-sectional study with a nested case-control study conducted in Cuiabá (MT). In the first stage, 1,066 parents and/or guardians answered the written questionnaire of the International Study on Wheezing in Infants. For the second stage, a sub-sample of 137 children were submitted to urinary cotinine dosing to assess exposure to tobacco smoke. Nonparametric tests and logistic binary regression were applied for possible risk factors. Among the infants exposed to tobacco, the majority were female (51.5%), race/color white (39.7%), with family income between R$ 800,00 and R$ 1,800.00 (52.9%) and their mothers had completed high school (42.6%). Frequent wheezing episodes (six or more episodes) and emergency room visits were significantly higher among infants exposed to tobacco. Urinary cotinine was detected in all 68 infants with reported exposure to tobacco, in 45 (66.2%) of them the levels were compatible with passive smoking. The mean level of cotinine in passive smokers was 32.4±8.6 ng/ml and the prevalence of passive smoking was 32.8%, being significantly higher among wheezing infants (41.8% vs 24.3%, p<0.030), mainly in recurrent sibilants (63.2% vs 20.7%, p<0.001). The higher the number of cigarettes consumed, the higher the level of urinary cotinine. Infants exposed to tobacco smoke are more likely to present recurrent wheezing compared to non-exposed ones. The evaluation of urinary cotinine levels is a good marker for exposure to cigarette smoke.