Behavioral Factors Predicting Serum Cotinine Concentrations of Male Smokers in a Japanese Community

Cigarette-derived toxic substances are inhaled along with the nicotine that is absorbed to satisfy the smoker's physical demand. Therefore, serum cotinine, a metabolite of nicotine, may be considered to be an indirect marker of absorption of the other toxic substances from smoking. However, few studies have examined factors related to serum cotinine concentrations in natural settings. The authors, therefore, have studied relations among patterns of smoking behavior and serum cotinine concentrations of community residents. Subjects were 60 smoking men living in the town of Yamasaki, Hyogo Prefecture, Japan. Number of daily cigarettes, depth of inhalation, hours from the last cigarette smoked and the total nicotine tolerance score were significantly, while neither nicotine-yields nor butt length of a discarded cigarette was correlated with serum cotinine concentrations. Multiple regression analysis confirmed that depth of inhalation and hours from the last cigarette smoked were independently significant. This finding suggests that attention only to self-reported daily number of cigarettes smoked may not be sufficient to detect smokers who are actually at high risk. Healthcare workers should also pay attention to smokers' patterns of smoking, particularly depth of inhalation. J Epidemiol, 1999 ; 9 : 143-145


Cigarette-derived
toxic substances are inhaled along with the nicotine that is absorbed to satisfy the smoker's physical demand.Therefore, serum cotinine, a metabolite of nicotine, may be considered to be an indirect marker of absorption of the other toxic substances from smoking.However, few studies have examined factors related to serum cotinine concentrations in natural settings.The authors, therefore, have studied relations among patterns of smoking behavior and serum cotinine concentrations of community residents.Subjects were 60 smoking men living in the town of Yamasaki, Hyogo Prefecture, Japan.Number of daily cigarettes, depth of inhalation, hours from the last cigarette smoked and the total nicotine tolerance score were significantly, while neither nicotine-yields nor butt length of a discarded cigarette was correlated with serum cotinine concentrations.Multiple regression analysis confirmed that depth of inhalation and hours from the last cigarette smoked were independently significant.This finding suggests that attention only to self-reported daily number of cigarettes smoked may not be sufficient to detect smokers who are actually at high risk.Healthcare workers should also pay attention to smokers' patterns of smoking, particularly depth of inhalation.J Epidemiol, 1999 ; The authors, therefore, have examined behavioral predictors of serum cotinine concentrations in smokers in a Japanese community.

MATERIALS AND METHODS
Subjects were male residents participating in a municipal health checkup examination in the town of Yamasaki, Hyogo Prefecture in October 1991.Sixty of 100 male participants identified themselves as current smokers.They were asked about their smoking behavior using the Fagerstrom's 8-item nicotine tolerance questionnaire 3) and about butt length of their discarded cigarettes.Fasting blood sample was taken for measurement of serum cotinine concentrations by gas-chromatograph 4).We used Pearson's correlation coefficients and multiple regression strategies to examine the relations among between cotinine concentrations and related factors.Three components of the nicotine tolerance questionnaire: number of cigarettes smoked daily, cigarette brand and depth of inhalation were also separately considered in the analyses.Nicotineyields were referred to the Japan Tobacco industry's publication shown in the internet web site (http://www jtnet.adjp/WWW/JT/JTI/outline/tobacco/syouhin J.html).
The following variables were dichotomized: depth of inhalation, always and sometimes or seldom into lungs; butt length, to the root and to the middle of cigarettes; and hours after the last cigarette smoked, within or over 6 hours; depth of inhalation.Because of moderately right skewness of the distribu- the last cigarette smoked were significantly, while neither nicotine-yields nor butt length was correlated with serum cotinine concentrations (Table 1).Multiple regression analysis of serum cotinine concentrations incorporating these six predictors (the nicotine tolerance score was modified with the rest the five items except the above-mentioned three items that had been separately used) confirmed depth of inhalation and hours from the last cigarette smoked were independently significant (Table 2).

DISCUSSION
It is well known that studies of serum cotinine concentrations need to adjust for hours from the last cigarette smoked.Therefore, the depth of inhalation was the sole meaningful predictor of serum cotinine concentrations in our study.Interestingly, number of cigarettes smoked daily was not proved to be a significant predictor in the multivariate analysis even though it was significantly correlated with serum cotinine concentrations in the univariate analysis.Being compatible with the previous report a, the present finding suggests that to place merit only on self-reported number of cigarettes smoked may not be sufficient to detect smokers with actual high risk.
Some human studies of experimental smoking reported positive relations between cigarettes' nicotine-yields and serum or salivary cotinine concentrations 6.7), while community studies did not confirm it 89).The former studies examined subjects' post-smoking sera; therefore, acute effect of smoking a cigarette might be somewhat exaggerated.Coutlas et al. 8) reported that number of cigarettes smoked daily was the most powerful and independent predictor of the salivary cotinine concentrations.They showed a cluster of smokers who consumed less than five cigarettes daily with low cotinine concentrations, which might make the correlation clearer than that observed in the present study.Whereas, all of the smokers in the present study habitually smoked five or more cigarettes per a day.This may be a reason of the difference observed between in the previous finding and in ours.They also showed that smokers of low-nicotine-yield cigarettes were likely to inhale smoke more deeply compared with the standard cigarette smokers, which is so called as self-titration or regulation of nicotine uptake 10,11) However, no such relationship was confirmed in this study.To explore this relation was not initially purposed, so the sample size of the present study is not enough to address this matter.
Absorption of nicotine from passive smoking was probably not a serious confounder in this study because the sensitivity of serum cotinine to reflect environmental tobacco smoke is reported to be, if anything, limited12).
We showed that inhalation depth was proved to be the most important predictor of serum cotinine concentrations in the community smokers.Healthcare workers should pay greater attention to smokers' patterns of smoking, particularly depth of inhalation to estimate their exposure to smoke and utilize this information by feedback to subjects for more effective health education.

Table 1 .
Pearson's correlation coefficients (and 95 percent confidence intervals) among serum cotinine concentrations and smokingrelated behavioral variables in sixty male smokers, Town of Yamasaki, Hyogo Prefecture, Japan, 1991.
Variables are continuous except depth of inhalation (into lungs, always versus sometimes or never) and butt length (to the middle versus to the root of a cigarette).a Serum cotinine concentrations and daily cigarettes are transformed by the square root .
lungs; butt length, to the root and to the mid of a cigarette; hours after the last smoking , within or over 6 hours.e Nicotine tolerance score is modified by excluding the three items simultaneously considered in this analysis.Adjusted R-square is 0.20.