Purpose: A frequently used valuation method for health state valuation is the time trade- off (TTO) method. Typically, valuation studies control for individual characteristics focusing on demographic variables like age, sex, education, and geography. We hypothesized that valuation of hypothetical health states are more prone to variance along other individual variables, including personality, beliefs, attitudes, and personal experience. The purpose of the study was to compare the impact of typical demographic variables to the impact of candidate variables from these other domains.
Method: 511 respondents participated in a web survey. The participants were fairly representative for the Norwegian population with respect to age and sex. Each participant valued eight health states of varying severity as described with the EQ-5D system. Additionally we asked questions about factors we hypothesized could affect their general willingness to trade away time: Agreement with euthanasia, number of children, the personality trait neuroticism, and the extent to which they considered themselves to be religious, to which extent they believed in a life after death. In a multivariate regression we used the TTO value as dependent variable and demographic variables and the other factors with potential influence as independent variables.
Result:
| Linear regression of TTO scores on individual variables | ||||||
| Coeff | Beta | p | ||||
| Intercept | 0.299 | <.001 | ||||
| sex (1 = female) | -0.02 | -0.019 | 0.322 | |||
| age (years) | -0.001 | -0.021 | 0.314 | |||
| 9-12 years of education | -0.046 | -0.04 | 0.28 | |||
| >12 years of education | -0.024 | -0.022 | 0.554 | |||
| Marital status (single vs. attached) | -0.014 | -0.012 | 0.561 | |||
| Children under 18 (dummy) | 0.048 | 0.043 | 0.036 | |||
| Belief in life after death (dummy) | 0.01 | 0.02 | 0.326 | |||
| Religiousity (5 point scale of agreement) | 0.001 | 0.001 | 0.947 | |||
| Attitudes toward euthanasia (mean of three 5 point scales) | -0.074 | -0.141 | <.001 | |||
| Neuroticism (normalized Z scores) | -0.028 | -0.049 | 0.012 |
Conclusion: Typical demographic variables did not significantly influence TTO values. However, having children in the home, attitudes toward euthanasia, and the personality trait neuroticism appear to significantly influence valuation of hypothetical health states. These variables were selected from their respective domains as likely candidates, and suggest that valuation of health states may be informed more by attitudes, personality, and experiences than the usual demographic variables. Variable relevance should be carefully considered.