Smoking and ischemic heart disease disparities between studies, genders, times, and socioeconomic strata

Abstract

Large, unexplained, but possibly related disparities exist between heart disease risks observed in differing genders, educational levels, times, and studies. Such heart disease disparities might be related to cumulative tobacco smoke damage (smoke load) disparities that are overlooked in standard assessments of point smoking status. So, I reviewed possible relationships between smoke load and heart disease levels across genders, educational strata, years, and leading studies. Smoker heart disease risk assessments in the Nurses Health Study (Nurses), Cancer Prevention Study-II (CPS-II), and British Doctors studies were compared and related to their likely selection and misclassification biases. Relationships between smoke loads and United States (US) education- and gender-related heart disease mortality disparities were qualitatively assessed using lung cancer rates as a smoke load proxy. The high heart disease mortality risks observed in smoking Nurses in 1980-2004 and in less educated US women in 2001 were qualitatively associated with their higher smoke loads and lower selection and exposure misclassification biases than in the CPS-II and Doctors studies. Smoking-attributable heart disease death tolls and disparities extrapolated from mortality ratios from the CPS-II and Doctors studies may be substantial underestimates. Such studies appear to have compared convenience samples of light smokers to lighter smokers instead of comparing representative smokers to the unexposed. Further efforts to minimize smoke exposures and better quantify cumulative smoking-attributable burdens are needed.