Measurement of self reported active exposure to cigarette smoke.

STUDY OBJECTIVE The number of cigarettes smoked per day is an imprecise indicator of exposure to cigarette smoke, and biochemical assessment of exposure is not always feasible. The aim of this study was to develop more accurate measures of self reported active exposure to cigarette smoke. DESIGN Mail survey in 386 smokers, retest at one month in 94 participants (24%), analysis of saliva cotinine in 98 participants (25%), collection of empty cigarette packs in 214 participants (55%), collection of cigarette butts in 107 participants (28%). Ten questions and items intended to assess active exposure to cigarette smoke were tested and compared with saliva cotinine, the Fagerström test for nicotine dependence, and self rated dependence. SETTING A population sample in Geneva, Switzerland, in 1999. PARTICIPANTS 323 daily smokers and 63 occasional smokers. MAIN RESULTS Measures that were associated with saliva cotinine included the number of cigarettes smoked per day (r(2)=0.36), smoking intensity (r(2)=0.40), the type of cigarettes smoked (regular versus light) (r(2)=0.04), smoking when ill (r(2)=0.15) and a single item rating of the total quantity of smoke inhaled (r(2)=0.27). A multivariate model combining the first four items explained the largest proportion of the variance in cotinine (r(2)=0.63), substantially more than was explained by the number of cigarettes per day alone, by 75% in all smokers and by 110% in daily smokers. CONCLUSIONS The study identified measures of exposure to smoke that reflect saliva cotinine better than the number of cigarettes per day. These measures can be used in studies of the dose related risk of smoking and in smoking reduction studies.