Candidate for the Lee B. Lusted Student Prize Competition
Purpose: To investigate the influence of patients’ own subjective life expectancy on their responses in time-trade off (TTO) questions used to value the patients’ own health states.
Methods: A sample of 145 patients with different severity levels of diabetic retinopathy were asked a set of TTO questions based on the statistical expected remaining survival for the age group of the respondent rounded to the closest ten. Next, the patients were asked how many years they were expecting to live themselves. The difference in years between the subjective life expectancy and the time used in the TTO questions was calculated and tested towards the results from the TTO questions in a univariate as well as in a multiple regression model including possible confounders (age, sex, HbA1c, duration of diabetes, type of diabetes, cardiovascular disease, nephropathy, neuropathy, retinopathy, smoking, education level, marital status).
Results: Of the 145 patients, 57.2% expected to live shorter than the time perspective used in the TTO question while 15.9% expected to live longer. In the remaining 26.9%, the statistical life expectancy used in the questions was equal to the life expectancy of the patients. The difference in years between the subjective and statistical life expectancy had a significant effect on the TTO valuation in the univariate (β=0.016 , p<0.001) as well as the multivariate model (β =0.010, p<0.001).
Conclusion: Patients’ own expectancies about their remaining life years influence their responses in the TTO questions. This suggests that the use of other time perspectives than the subjective life expectancy of the respondents could result in biased TTO valuations.
See more of: The 33rd Annual Meeting of the Society for Medical Decision Making