Duration changes and decision-making in DCE_TTO: evidence from SF-6Dv2

This study investigated the impact of changes in health state duration in a discrete choice experiment where duration is an attribute (DCE_TTO).

A sample of the general population in Quebec, Canada, completed DCE_TTO in two phases using SF-6Dv2. In the first phase (DCE_original), participants were presented with binary choice sets, each containing two health states and associated durations. In the second phase (DCE_changed), they completed the same choice sets as before, but with modified durations. Adjustments were made based on participants' initial responses. Durations were 1, 4, 7, 10, 14, and 20 years. McNemar's Test was used to evaluate the change in respondents' choices before and after the duration modification.

A total of 411 participants were included. Significant increases in duration of the option not chosen (by a factor of two or more) led it to become the preferred option (p < 0.05). A decrease in the duration of the option chosen could still lead to its acceptance. Overall, participants showed a strong anchoring effect of their initial choice, while changes in duration had a moderate positive effect on the likelihood of switching choices.

Findings highlight non-linear effects of time on preferences and have important implications for the design of DCE_TTO studies.