Why a million-person cohort?
Statisticians working on the proposal for the American Gene and Environment Study concluded that a cohort of this size should be adequate for analysis of gene-gene interactions of the type anticipated to play a role in cancer susceptibility. An article by Francis Collins in Science mentioned the need for a large-scale longitudinal human cohort, taking tissue samples pre- and post-disease, to make best use of the technology – not just after the disease has spread. Case control studies typically yield biased information because they are based on the surviving subset of people with that disease. Few studies have collected long-term human tissue samples. To design such a large population study is obviously challenging – deciding what to analyze for and how to obtain a large enough dataset that the signal-to-noise ratio is robust in the face of real human variation. The difficulties are compounded by the high cost of the undertaking, which necessitates that the cohort be applicable to resea
