Mispredicting and misremembering: patients with renal failure overestimate improvements in quality of life after a kidney transplant

Objective: People tend to overestimate the impact that future events will have on their quality of life. In the case of a medical treatment like kidney transplant, this should result in biased predictions--overestimates of how much the transplant will benefit quality of life. The authors surveyed kidney transplant patients, both before and after transplant, to test whether they would overestimate the benefits of a successful transplant for their quality of life.

Design: The authors interviewed 307 patients on a waiting list for cadaveric renal or renal-pancreatic transplant, and 195 patients one year after a successful transplant. A sub sample of patients were interviewed both before and after transplant.

Main outcome measures: The survey included measures of quality of life, both in terms of an overall estimate (0-100), and across sub domains, including health, employment, and travel.

Results: Cross-sectional results suggested that overall quality of life improved after transplant, but the predictions of pretransplant patients overestimated the magnitude of the improvement (p < .01). In addition, patients predicted large improvements in specific life domains that did not change. These results were confirmed in longitudinal, prospective analyses. Additional analyses showed that posttransplant patients recalled their pretransplant quality of life to be much lower than what they had reported at the time.

Conclusion: Consistent with an impact bias, patients substantially overestimated the benefits of a successful kidney transplant, both in terms of predictions of life after treatment, and in their memories of QOL before the transplant.