Finally, although individual demographical factors and stage of cancer were adjusted for in this study, other unselected factors such as dietary, medical care, and lifestyle factors of smoking and alcohol con- sumption may also confound the observed association. As information on these factors is not available in this study, we could not control for their potential confounding effects. However, although demographic distributions between LA and Honolulu are much differ- ent, we only studied one race of White in this study. Thus, the influences of different culture and dietary habits are unlikely to explain the significant differences in length of survival from respiratory cancer. Moreover, both areas in this study are urban areas with the same healthcare system in the United States, which is also improbable to account for this significant difference. In addition, as cancer patients, current tobacco use and alcohol consumption are not common; thus the confounding effects of these factors should be limited