Background: Look-back investigations of populations of patients admitted to major tertiary-care hospitals in the 1980s found a 2-year posttransfusion mortality rate in excess of 50 percent. To quantify the association of blood transfusion with mortality in a more broadly based population, a cohort of all residents of a United States county who underwent transfusion in 1981 was studied. Study Design and Methods: Retrospective cohort study comprised 802 county residents. Complete follow-up (until death or for 10 years) was available on 93.9 percent. Results: The median length of survival was 95.0 (+/- 2.5) months. Twenty-four per cent of patients died within 1 year after the transfusion, 30 percent within 2 years, 40 percent within 5 years, and 52 percent within 10 years. The relative risk of death within 10 years increased by 4.1 percent per unit of red cells (p<0.0001), by 1.2 percent per unit of platelets (p = 0.0003), and by 7.3 percent per unit of fresh-frozen plasma (p = 0.0018) received in 1981, after adjustment for the effects on mortality of age, gender, and number of days of hospitalization in 1981. Conclusion: Receipt of a blood transfusion can be used as a descriptive epidemiologic index of morbidity in the general population, as it is independently predictive of mortality, adding to the predictive value of age, gender, and previous hospitalization. There is a dose-response relationship between the amount of blood components received and a reduction in the subsequent length of survival. However, when a county's entire population is studied, posttransfusion mortality due to underlying disease is substantially lower than that previously reported in look-back investigations.
