Proxy reports were obtained at MATCh baseline home interviews on mothers’ smoking status. Mothers’ smoking status was assessed with the question “Does your mother/stepmother smoke?” Positive responses (“Yes”) from the adolescent were categorized as “current smoker” and compared with negative responses (“No”). Mothers self-reported their smoking status at two timepoints. The mothers (n=1,213) had previously provided data (median time 1 year previously; M=1.03 years; SD=1.17) when they were enrolled into the cohort (Query 1). Smoking behavior among mothers was assessed with the question “Have you smoked at least 100 cigarettes (five packs) in your lifetime?” Mothers who responded “Yes, currently smoke” were categorized as current smokers and were compared with never-smokers and quitters. About a year and a half after the adolescent had enrolled in MATCh and had completed his/her baseline interview, mothers (n=1,113) answered the same question via phone (M=1.38 years; SD=0.47). A total of 1,029 (84.8% overlap or 93.1% overlap) mothers provided data at both timepoints.

Mothers and adolescents in each group for whom proxy reports or mothers’ self-reports on smoking were not available were excluded from the analysis (n=115 for first query and n=223 for second query). Eight adolescents who did not live with their mothers were also excluded from this analysis.

Table 2 presents bivariate analysis stratified by the adolescent’s demographic characteristics and smoking status. The kappa statistic indicated that regardless of query, mother–daughter pairs reported higher rates of agreement compared with mother–son pairs. Regardless of query, younger adolescents’ (11-year-olds) reports agreed with their mothers’ reports more than their older peers, as did the reports from adolescents born in the United States compared with those born in Mexico. In addition, adolescents who had experimented with smoking reported lower rates of agreement compared with the other groups.

Table 3 presents the results of the logistic regression analysis examining factors associated with disagreement. Since the kappa values in general were better from the first query, logistic regression was conducted using data from first query only. The results of the first logistic regression did not identify any significant risk factors. However, the results from the second logistic regression analysis revealed that 13-year-olds were 2.67 times (CI=1.22–5.92) more likely to disagree with their mothers compared with 11-year-olds, and experimenters were 2.68 times (CI=1.23–5.82) more likely to disagree compared with nonexperimenters.

Although concordance between mothers’ first query and second query was good, one factor that could contribute to the discordant responses between the mothers and their children is the fact that some of the mothers’ smoking status changed between two queries. Therefore, the accuracy of the child’s report could depend on when the children provided data in relation to when their mothers provided data. Overall, 4.5% (46 women) reported a change in smoking status between the two queries; 19 women reported that they started smoking and 27 women reported that they quit smoking, suggesting that this impact was limited.

To be consistent with previous research (Barnett et al., 1997), we compared reports of current smoking with reports of never and quitting. However, when we compared reports of current with reports of never smoking only, the kappa values at the second query increased, Κ = 0.62 (95% CI = 0.51–0.72), as did the Κ value based on mother–mother reports, Κ = 0.70 (95% CI = 0.59–0.80; data not shown).

We identified two factors associated with discordant smoking reports. In contrast to Barnett et al. (1997), we found that younger adolescents, not older ones, were more likely to provide concordant responses with their mothers. However, the adolescents in Barnett et al. ranged in age from 9 to 13 years, compared with 11–13 years in our study. A closer inspection of concordance rates observed by Barnett et al. reveals that, consistent with our results, 11-year-olds had the highest concordance rates.

We also found that experimenters were more likely to misclassify their mothers’ smoking status than nonexperimenters. Of those adolescents who disagreed, 63.3% misclassified their mothers as smokers. Because maternal smoking places mothers’ adolescent children at increased risk of smoking (Wilkinson et al., 2008), it is possible that the adolescents’ own smoking behavior influenced their decision to classify their mothers as smokers. In addition, because age and experimentation were moderately correlated (r = 0.22, p < .01), older adolescents may have interpreted some parental smoking behaviors, like experimentation, as a manifestation of earlier smoking and therefore misclassified their mothers (Pomerleau et al., 2005).

Overall, the kappa values in our study were moderate but the percent agreements were high. It has been suggested that kappa values are influenced by the bias and prevalence of the outcome (Banerjee & Fielding, 1997), such that a high prevalence index (when the prevalence of a positive rating is very high or very low) results in lower kappa values (Sim & Wright, 2005). In our study, the prevalence of nonsmoking was very high, and the bias, or the extent to which raters disagree, was also low, leading to the moderate kappa values.

Our study had several limitations. First, the mothers’ self-reported smoking status was not biochemically validated. Second, smoking data from fathers were limited, so we could not reliably compare father and adolescent reports. Third, the mother and adolescent data were not collected concurrently. However, maternal data were available from two timepoints, one before and another after the adolescents’ reports on their mothers’ smoking behavior. Fourth, unfortunately while we have detailed data from the mothers about their smoking behavior (e.g., self-reported level of nicotine dependence, number of cigarettes smoked per day, when first cigarette is smoked during the day), we did not have similar information from the children regarding the mothers’ smoking behavior. Therefore, we are unable to address the important issue of whether adolescents can provide more detailed information about their parents’ smoking behaviors, other than whether or not they do/did smoke.