Ascertainment and anticipation in family studies

Many human diseases show anticipation; that is, disease occurs earlier (or with greater severity) in successive generations. In a computer simulation, we assessed the degree of anticipation that one would expect to see in two -generation breast cancer families, Under reasonable assumed distributions for age at cancer onset, number of children, and mortality, we find a consi stent earlier mean age at diagnosis in daughters than in mothers, but the s ame mean age at diagnosis in affected aunts and nieces. We compare these re sults with published pedigree data for familiar breast cancer that show sub stantial anticipation in affected daughters compared to their mothers. We f ind that at least some anticipation is expected in human disease families e ven when the disease is stable and families are ascertained without obvious sampling bias. We further demonstrate that such anticipation is reduced wh en comparing affected children to the parents' affected siblings. Copyright (C) 2000 S. Karger AG, Basel.