Re. The Association Between Childhood Leukemia and Population Mixing: An Artifact of Focusing on Clusters?

To the Editor: The recent paper on childhood leukemia and population mixing by Berrie et al1 contains important omissions and inaccuracies with respect to population mixing, a term one of us coined in relation to extreme examples of rural–urban mixing. Its investigation by Kinlen and colleagues2 in 1990–2001 included rural new towns, rural districts receiving the greatest proportions of children evacuated from large urban centers during the...