Determinants of salivary cotinine level: a population based study in Brazi

Abstract

A cross-sectional population-based study was conducted to assess, in active smokers, the relationship of number of cigarettes smoked and other characteristics to salivary cotinine concentrations. METHODS: A random sample of active smokers aged 15 years or older was selected using a stepwise cluster sample strategy, in the year 2000 in Rio de Janeiro, Brazil. The study included 401 subjects. Salivary cotinine concentration was determined using gas chromatography with nitrogen-phosphorus detection. A standard questionnaire was used to collect demographic and smoking behavioral data. The relation between the number of cigarettes smoked in the last 24h and cotinine level was examined by means of a nonparametric fi tting technique of robust locally weighted regression. RESULTS: Signifi cantly (p<0.05) higher adjusted mean cotinine levels were found in subjects smoking their fi rst cigarette within fi ve minutes after waking up, and in those smoking 1–20 cigarettes in the last 24h who reported inhaling more than ½ the time. In those smoking 1–20 cigarettes, the slope was signifi cantly higher for those subjects waiting for more than fi ve minutes before smoking their fi rst cigarette after waking up, and those smoking “light” cigarettes when compared with their counterparts. These heterogeneities became negligible and non-signifi cant when subjects with cotinine >40 ng/mL per cigarette were excluded. CONCLUSIONS: There was found a positive association between self reporting smoking fi ve minutes after waking up, and inhaling more than ½ the time are consistent and higher cotinine levels. These can be markers of dependence and higher nicotine intake. Salivary cotinine proved to be a useful biomarker of recent smoking and can be used in epidemiological studies and smoking cessation programs.