Aim: To investigate if subjective life expectancy (SLE) impacts the willingness to trade-off (WTT) and the number of years traded-off in a 10-years time trade-off (TTO) exercise to obtain health state valuations.
Methods: An Internet-based questionnaire was administered in a sample representative for the Dutch general public. Next to basic demographic characteristics and SLE, respondents were asked to perform three TTO exercises. The following EQ-5D health states were included 21211 (TTO1), 22221 (TTO2) and 33312 (TTO3). The WTT was studied using a probit regression model. The number of years traded-off was investigated using a generalized negative binomial regression model. The independent variables used in both models were age, gender, quality of life, education, the difference between age and expected age of death (SLE), and a variable indicating whether the SLE was less than 10 years (SLE<10).
Results: Three hundred and thirty nine respondents completed the questionnaire. The mean utility scores were 0.96 (TTO1), 0.94 (TTO2) and 0.79 (TTO3). The probit model showed that SLE was the only variable with a significant influence on WTT. The gnbreg showed that the number of years traded-off was also significantly influenced by SLE. In addition, age and education significantly influenced the number of years traded-off.
Conclusion: The WTT years and the number of years traded-off were both influenced by SLE in 10-years TTO exercises. Reducing remaining life expectancy to 10 years in a TTO may thus increase loss aversion and, especially in respondents losing relatively many expected life years, diminish WTT and the amount of time traded off.
(c) 2008 John Wiley & Sons, Ltd.