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Quality of Life Research
Published in: Quality of Life Research 1/2012

Open Access 01-02-2012

Constantly Proving The Opposite? A test of CPTO using a broad time horizon and correcting for discounting

Authors: Arthur E. Attema, Werner B. F. Brouwer

Published in: Quality of Life Research | Issue 1/2012

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Abstract

Purpose

An important assumption underlying the quality-adjusted life year (QALY) model is that people trade off life years against health in the same proportion irrespective of the number of remaining life years. This is known as the constant proportional trade-offs (CPTO) condition. Previous studies have produced mixed empirical evidence about the validity of CPTO. This paper is the first to test CPTO using the time trade-off (TTO) method for a broad time horizon.

Methods

In a sample of 83 students, we use a choice based TTO protocol to elicit TTO scores for back pain, using ten different gauge durations ranging between 1 and 46 years. The TTO scores are corrected for discounting, which is elicited by means of the direct method.

Results

We find average TTO scores varying between 0.72 and 0.81. Although the scores do not differ much for different durations in absolute terms, some differences are significant, rejecting CPTO, with and without correcting for discounting. No clear relationship between TTO scores and gauge duration is found. An anchoring and rounding heuristic to some extent explains our results.

Conclusions

Our findings highlight the importance of elicitation methods and context dependencies in QALY measurement and warrant detailed investigation of their influence.
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Metadata
Title
Constantly Proving The Opposite? A test of CPTO using a broad time horizon and correcting for discounting
Authors
Arthur E. Attema
Werner B. F. Brouwer
Publication date
01-02-2012
Publisher
Springer Netherlands
Published in
Quality of Life Research / Issue 1/2012
Print ISSN: 0962-9343
Electronic ISSN: 1573-2649
DOI
https://doi.org/10.1007/s11136-011-9917-4

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