Discordant results due to residual confounding associated with smoking are less likely given that, as one of the few identified risk factors, most epidemiologic studies have included tobacco use in their analyses of alcohol consumption and pancreatic cancer risk. Indeed, in several studies that reported a positive association between alcohol and pancreatic cancer, the association persisted even among non-smokers [16, 17, 20, 36]. In our study, data were consistent with persistent increased risk among non-smokers, but not statistically significant. Notably, the number of never smokers available for analysis in our study required pooling of data from never smokers with those who quit smoking over 15 years prior to interview; this may have biased our estimates comparing risk among non-smokers to smokers toward finding a smaller risk difference than actually present. However, because there was a small sample of never smokers, and the ability to adjust for more detailed smoking characteristics (such as pack-years of smoking) was limited, it is possible that residual confounding due to smoking cannot be completely excluded.
