Values for health states with different life durations.

BACKGROUND

Recent research suggests that the value of health states may depend on their duration, implying a more complex relationship between quality and quantity of life than the standard linear relationship assumed in the quality-adjusted life years (QALY) model.

OBJECTIVE

This study models how duration affects the value of health states, using discrete choice data.

METHODS

A study was conducted comprising health profiles including various durations. Health states were described with the EQ-5D. Duration was introduced as a sixth domain with six levels (1, 5, 10, 15, 30, 50 years). Sixty pairs of health profiles were selected, applying a Bayesian approach. Two hundred eight university students self-completed the computerized response tasks. Data were analyzed with a conditional logistic regression model.

RESULTS

There is clear evidence for non-linear values for duration, that is, preferences for duration are more accurately described by a logarithmic function.

CONCLUSIONS

In discrete choice experiments using health states with different durations, these data present the first evidence for decreasing marginal utility for duration. Our results suggest that refinement of the standard QALY framework may be needed for states with a long duration.