Exercise: Psoriasis and eczema, answer 2

Question 2: What is meant by ‘time trade off’ in this context? What problems may arise in using such a measure? (The quoted results for this, 0.88 and 0.73, are the proportion of a nominal 30 years of remaining life which people would reduce their life to in order to be disease free.)

Suggested answer

In this approach people are given a scenario such as ‘Imagine you have 30 years left to live in your current health state, how many of these years would you give up to be in perfect health?’ Hence psoriasis patients would trade off an average of (1 – 0.88) = 0.12 times 30 years of life, 3.6 years. The more years that the respondent would be willing to trade off, the lower the quality of life in that state.

The problem is that many respondents find the idea difficult to understand.

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