Elisabetta Barbi

Beltrán-Sánchez et al. (1) based their comment on calculations for their quantity T , projected for cohorts with n members alive at age 105. The authors call T “maximum survival age,” but that is misleading. T is not an age with low probability of being exceeded. In the model in use, the probability of T being exceeded is more than 63%. The lifespan of the last survivor out of n is a random quantity.

Mortality rates level off at extreme age The demography of human longevity is a contentious topic. On the basis of high-quality data from Italians aged 105 and older, Barbi et al. show that mortality is constant at extreme ages but at levels that decline somewhat across cohorts. Human death rates increase exponentially up to about age 80, then decelerate, and plateau after age 105. Science, this issue p.