Seasonality in living kidney donation in the United States from 1995-2019

For nearly two decades, the annual number of US living kidney donors has been characterized by worrying patterns of decline and no factors have been identified to explain and reverse these patterns. Evidence suggests that there is seasonality in living kidney donation; herein we investigate whether potentially modifiable social, economic, and structural issues might explain this seasonality. Using donor-registry data from the Scientific Registry of Transplant Recipients, we described this seasonality in living kidney donation and used Poisson regression stratified by both donor-recipient biological relationship and estimated household income tertile to quantify these trends. In every decade from 1980-2020, there was a summer-only surge in living kidney donations (13%-25% for biologically related donors and 10%-17% for unrelated donors). This summer-only surge was evident for the months of June, July, and August when compared with January for each given year and statistically significant in some groups (range of incidence rate ratio [IRR] for related donors: 1.05-1.34; IRR for unrelated donors: 1.08-1.19). We observed this summer-only surge across all three income tertiles ($73,544+, $52,635- $73,544, and <$52,635) and regardless of donor-recipient relationship. Seasonal variation in donation is associated with structural factors, which may serve as potential targets for interventions to increase donation.