Modelling valuations for health states: the effect of duration.

An important issue which has been raised in the measurement of health status is the effect that the time spent in a health state may have on the way that state is perceived. Recently a set of valuations for health states defined in terms of the EuroQol Descriptive System was generated from a study of over 3000 members of the UK general public. The valuations were elicited using the visual analogue scale (VAS) and time trade-off (TTO) methods and were for states that lasted for 10 years. Using VAS valuations for states lasting 1 month, 1 year and 10 years derived from a subset of respondents to the general population study, this paper presents valuation "tariffs" for all EuroQol states based on the different durations. The results support those of previous studies which suggest that poor states of health become more intolerable the longer they last. Such findings suggest that the results of studies in which the value given to a health state is assumed to be linearly related to the time spent in that health state should be treated with caution and subjected to sensitivity analysis over an appropriate range of values.