Statistically significant interactions between diplotypes within GSTM3 and in utero smoke exposure and personal smoking at age 18 were not observed (Additional file 3: Tables S9a and S9c).
* Comprised of SNPs as described in the Results section; †Models adjusted for in utero smoke exposure and personal smoking status; ‡ Global F-test p-value: significance of interaction; § After adjustment for false discovery rate (FDR).
Because women exposed to in utero tobacco smoke were more likely to smoke as adults, and smokers tend to be different from nonsmokers regarding socioeconomic and other risk factors (data not shown), multiplicative interactions between in utero tobacco smoke (yes/no) and personal smoking (yes/no) were examined in all the models.
Additionally, no significant interactions with in utero smoke exposure, SHS exposure, and personal smoking at age 18 were observed (Additional file 3: Tables S10a-c).
Also reported yearly was information on the presence of secondhand tobacco smoke in the home (SHS) and personal smoking by the child.
These associations persisted after adjustment for confounding factors including adult weight, exposure to cigarette smoke in utero and during childhood, personal smoking, socio-economic status, asthma and gestational age.
Next, we expanded the models using covariates that were associated with either PM2.5 or CIMT, including indicator variables for current second-hand smoke exposure and current and former personal smoking.
The effect of GSTP1 on asthma and wheezing did not differ with respect to sex, secondhand-smoke exposure, number of smokers in the household, personal smoking, and ambient air pollutants including ozone, nitrogen dioxide, and PM2.5 and PM10 (data not shown).
Finally, given that some of the signals found for prenatal smoke exposure have also been identified in a study of personal smoking of adolescents (30), any apparent persistent effect of maternal smoking on offspring methylation profile at later ages may be explained by smoking of the adolescents themselves.
Personal smoking status was based on the questions "At the present time, do you smoke cigarettes daily, occasionally, or not at all?" In addition to this, a question was asked regarding past smoking.
Elizabeth Holly, a professor of epidemiology and biostatistics at the University of California, San Francisco, said, "It's quite good we've made some progress in our advance against cancer, but what it really is reflecting, fortunately, is a change in personal smoking habits and early detection and treatment in prostate, colorectal and breast cancer".
