Chris Sampson ~ Considering Time Perception
Chris works in the IMH building for the NIHR CLAHRC and runs The Academic Health Economists’ Blog: http://aheblog.com/.
In economic evaluations in health, time matters. More time in a bad health state is necessarily worse (or no better) than a smaller amount of time in said health state. Likewise, the value of an intervention increases with the duration of benefit. The standard QALY framework takes this into account. Furthermore, time preferences matter. Economists deal with this in a present value framework; discounting future costs and benefits. But there is another aspect of time which is not taken into account; time perception. Issues surrounding our perceptions of time recently appeared in the usual pop science outlets following the release of Claudia Hammond’s new book ‘Time Warped‘. As medical, neurological and psychological understandings of time perception improve, is it time economists weighed in?
Economists have considered the effects upon time perception of things like ‘awe‘ and the cognitive resource demands of tasks, while others have investigated the interaction between time preferences and time perceptions. It seems none have investigated the implications for an area in which time perceptions might play their most important role; health.
Why might it matter?
Time is an abstract idea, but economists rarely treat it as such. This means that people’s perceptions of time are overlooked. This may be a reasonable approach if we are working at the mean and people’s perceptions of time are consistent across health states. But what if they aren’t? Consider a basic illustrative QALY example:
- Scenario A: 2 weeks in 0.8 health, followed by 2 weeks in full health
- Scenario B: 1 week in 0.6 health, followed by 3 weeks in full health
Clearly these scenarios give the same QALY result. If one perceives time to pass more slowly in a worse health state then we might be able to add to the scenarios that in ‘A’ the first 2 weeks “feels like 3 weeks”, while in ‘B’ the first week “feels like 2 weeks”. If we were to weight the QALY values in these periods according to perceived time we would have a preference for scenario A. With these re-weightings, 2 weeks of 0.8 in scenario A would become equivalent to 2 weeks of 0.53, while 1 week of 0.6 in scenario B would become equivalent to 1 week of 0.3; increasing the difference between the two health states.
We all experience fluctuations in our own time perception. Time flies when we’re having fun. It might fly when we’re healthy too. It may be the case that a general and testable model of time perception exists in health. The most likely relationship seems to be that being in poorer health would be associated with a perception of time moving more slowly. There may also be differences in time perception between different groups of people (men and women, children and the elderly) that we may or may not want to adjust for. Some interesting implications of time perceptions for the burden of waiting times have already been identified.
Particular health conditions can affect an individual’s perception of time, and this is where the consideration of time perceptions could be crucial. Children with ADHD, for example, have been shown to perceive time in very different ways to those without ADHD. Likewise, cancer patients with evidence of disease have been found to perceive time as progressing more slowly, compared with those without. If a condition causes individuals to perceive time to move more slowly in a consistent and measurable way, then specific rules could be established to assign greater weight to treatments for said condition.
The relationships above are all testable and quantifiable. Time perceptions can be easily tested by denying well and unwell patients access to a clock and calendar, and then asking them about the ways in which they perceived their time in these states. It is important to note that during these times our perception of time may be affected by other things; whether we are confined to a hospital bed, stuck in the office or asleep at home. All of these things could be controlled for in an experiment.
The real question is whether or not we (the public) want to take this into account or not. If the public’s stated preferences do not reflect the effects of time perception then should we artificially weight their preferences to do so? The issue seems analogous to that of adaptation (to which time perceptions would no doubt be subject!). Public valuations of the effects of time perceptions could be captured with the usual time trade-off, standard gamble or discrete choice experiment techniques. One difficulty would be in ensuring that there is no double-counting. It seems likely that this would not apply in the specific applications, where the general public’s valuations would not consider ADHD’s effects on time perception, for example. However, it seems possible (likely, even) that the general public would consider time perception effects associated with being generally unwell.
Perceptions of time have been discussed in economic and health economic literature in respect to experienced utility and biases of memory in retrospective valuations. There has been little contribution to theories about individuals’ present time perception. I believe it may be time for these ideas to be explored further, particularly in relation to specific health conditions, and applied to preferences and expected utility in health.
How do you see time perceptions influencing quality of life? To what extent do you think differences in time perception either could or should influence health care decision making? Please comment below.