• molecular epidemiology

Recent scientific, political, industrial, and public relations efforts to publicise the first interpretations of the human genome sequence raised unprecedented social expectations towards the health sciences^1–6; yet, prudence seems warranted when assessing the relevance of emerging genomic knowledge to lessen the burden of illness in human populations.^7–9 Among the formidable tasks that lie ahead, it will be important to achieve a proper understanding of how genes and the environment interact to cause human disease.^10–14 This aim will partly depend on how molecular epidemiological studies are conducted. Long viewed as a promising approach,¹⁵ molecular epidemiology is no longer in its infancy.^16–25 Figure 1 shows that the number of studies ascribed to molecular epidemiology increased dramatically during the past decade. Yet, as shown in table 1 and figure 2, “molecular epidemiological” studies are just a fraction of studies attempting to integrate epidemiological, genetic, and molecular dimensions of disease. Even if nowadays some features of molecular epidemiological studies retain some novelty, other basic challenges have always been undisputed.¹¹ Prominently, the need to integrate valid biological, clinical, and epidemiological information from unbiasedly selected populations. Indeed, tumour tissue procurement and, more generally, the availability of biological samples are crucial in molecular epidemiology. However, although completeness of the “biological study base” is frequently hampered by ethical, clinical, and logistic factors, these are rarely analysed in depth. Unaccountably, molecular epidemiological studies often fail to properly assess whether selection biases affect their results.²⁶ Exceptions do exist, of course. One is the study by Slattery et al—interestingly, published in Mutation Research Genomics.²⁷ The authors were able to collect blocks and extract DNA for 2117 of 2477 people (86%) for whom they had permission to obtain tumour blocks. They found no differences in age, tumour site, …