As a group, blacks have higher mortality due to lung cancer and heart disease than whites. Compared with whites, Hispanics have lower or similar mortality due to lung cancer and heart disease. Blacks and Hispanics tend to have lower IQs than whites. In general, people with low IQ tend to have higher mortality due to lung cancer and heart disease. Perhaps a gene that modulates IQ also has effects on mortality due to lung cancer and heart disease. These concepts are discussed in greater detail in a paper (Cognitive epidemiology of ethnic health and the CHRM2 vagal vigour hypothesis) that is available on the Nature Precedings website.

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