Aging of registered stem cell donors: implications for donor recruitment.

With more than 11 million registered stem cell donors worldwide and limited resources for health systems, it seems questionable if investments in ongoing donor recruitment are useful. Since there is evidence that transplant outcomes are better with younger donors, the age distribution of registered donors is highly relevant in this context. One might argue that the usefulness of a donor file decreases if there is no new donor recruitment not only as a result of loss of donors who reach the age limit for donation but also since those donors who remain in the file get older. We established a multivariate model to quantify this effect and to estimate the number (designated R) of donors who must be recruited annually to keep donor file usefulness constant. The model is applied to real data from DKMS German Bone Marrow Donor Center. R exceeds the number of donors who reach the age limit by factors up to 7.3. The model can serve as an easy-to-use tool for strategic donor registry planning. Our results suggest that analyses regarding optimal size of donor registries should also include the age distribution of registered donors.