Association between time to first cigarette after waking up and salivary cotinine concentration.

Introduction: The time to first cigarette smoked after waking up appears to be a good predictor of plasma and urine cotinine levels; however, collection of blood and urine is difficult in population-based studies and may influence participation. We aimed to test whether time to first cigarette is associated with salivary cotinine.

Methods: We used data from a cross-sectional study on a representative sample of the general population of Barcelona, Spain. We gathered information on smoking by means of a questionnaire and collected saliva for cotinine analysis. Of 1,245 participants, 22.9% were daily smokers, and the final sample for analysis consisted of 210 daily smokers.

Results: There were significant associations between salivary cotinine and time to first cigarette, between cigarette consumption and time to first cigarette, and between salivary cotinine and cigarette consumption. Salivary cotinine had decreased as time to first cigarette increased. After adjusting for cigarette consumption and sex, there were significant differences in mean salivary cotinine according to time to first cigarette (≤ 5 min: 219.2 ng/ml; 6-30 min: 175.8 ng/ml; 31-60 min: 168.5 ng/ml; >60 min: 137.2 ng/ml). All paired comparisons were significant (p < .001) except in the 6- to 30-min group versus the 31- to 60-min group (p = .701).

Conclusions: After adjustment for the number of cigarettes smoked in the last 24 hr, time to first cigarette is associated with salivary cotinine concentration.