Chris Sampson’s journal round-up for 13th March 2017

Every Monday our authors provide a round-up of some of the most recently published peer reviewed articles from the field. We don’t cover everything, or even what’s most important – just a few papers that have interested the author. Visit our Resources page for links to more journals or follow the HealthEconBot. If you’d like to write one of our weekly journal round-ups, get in touch.

The effects of exercise and relaxation on health and wellbeing. Health Economics [PubMedPublished 9th Month 2017

Encouraging self-management of health sounds like a good idea, but the evidence is pretty weak. As economists, we know that something must be displaced in order to do it. This study considers the opportunity cost of time and how it might affect self-management activity and any associated benefits. Employment and education are likely to increase income and thus facilitate more expenditure on exercise. But the time cost of exercise is also likely to increase, meaning that the impact on demand is ambiguous. The study uses data from a trial of self-management support that included people with diabetes, COPD or IBS. EQ-5D, self-assessed health and the amount of time spent ‘being happy’ were all collected. Information was available for 12 different self-management activities, including ‘do exercises’ and ‘rest and relax’, and the extent to which individuals did these. Outcomes for 3,472 people at 12-month follow-up are estimated, controlling for outcomes at baseline and 6 months. The study assumes that employment and education affect health via their influence on exercise and relaxation. That seems a bit questionable and the other 10 self-management indicators could have been looked at to test this. People in full-time employment were 11 percentage points less likely to use relaxation to manage their condition, suggesting that the substitution effect on time dominates as the opportunity cost of self-management increases. Having a degree or professional qualification increased the probability of using exercise by 5 percentage points, suggesting that the income effect dominates. Those who are more likely to use either exercise or relaxation are also more likely to do the other. An interesting suggestion is that time preference might explain things here. Those with more education may prefer to exercise (as an investment) than to get the instant gratification of rest and relaxation. It’s important that policy recommendations take into consideration the fact that different groups will respond differently to incentives for self-management, at least partly due to their differing time constraints. The thing I find most interesting is the analysis of the different outcomes (something I’ve worked on). Exercise is found to improve self-assessed health, while relaxation increases happiness. Neither exercise or relaxation had a (statistically significant) effect on EQ-5D. Depending on your perspective, this either suggests that the EQ-5D is failing to identify important changes in broad health-related domains or it means that self-management does not achieve the goals (QALYs to the max) of the health service.

New findings from the time trade-off for income approach to elicit willingness to pay for a quality adjusted life year. The European Journal of Health Economics [PubMedPublished 8th March 2017

The question ‘what is a QALY worth’ could invoke any number of reactions in a health economist, from chin scratching to eye rolling. The perspective that we’re probably most familiar with in the UK is that the value of a QALY is the value of health foregone in order to achieve it (i.e. opportunity cost within the health care perspective). An alternative perspective is that the value of a QALY is the consumption value of health; how much consumption would individuals be willing to give up in order to obtain an additional QALY? This second perspective facilitates a broader societal perspective. It can tell us whether or not the budget is set at an appropriate level, while the health care perspective can only take the budget as given. This study relates mainly to decisions made with the ‘consumption value’ perspective. One approach that has been proposed is to assess willingness to pay for a QALY using a time trade-off exercise that incorporates trade-offs between length and quality of life and income. This study builds on the original work by using a multiplicative utility function to estimate willingness to pay and also bringing in prospect theory to allow for reference dependence and loss aversion. 550 participants were asked to choose between living 10 years in their current health state with their current salary or to live a reduced number of years in their current health state with a luxury income (pre-specified by the participant). Respondents were also asked to make a similar choice, but framed as a loss of income, between living 10 years at a subsistence income or fewer years with their current income. A quality of life trade-off exercise was also conducted, in which people traded reduced health and a lower income. The findings support the predictions of prospect theory. Loss aversion is found to be stronger for duration than for quality of life. Individuals were more willing to sacrifice life years to move from subsistence income to current income than to move from current income to luxury income. The results imply that quality of life and income are closer substitutes than longevity and income. That makes sense, given the all-or-nothing nature of being alive. Crucially, the findings highlight the need to better understand the shape of the underlying lifetime utility function. In all tasks, more than half of respondents were either non-traders or over-traded, indicating a negative willingness to pay. That should give pause for thought when it comes to any aggregation of the results. Willingness to pay studies often throw up more questions than answers. This one does so more than most, particularly about sources of bias in people’s responses. The authors identify plenty of opportunities for future research.

Beyond QALYs: multi-criteria based estimation of maximum willingness to pay for health technologies. The European Journal of Health Economics [PubMed] Published 3rd March 2017

Life is messy. Evaluating things in terms of a single outcome, whether that be QALYs, £££s or whatever, is necessarily simplifying and restrictive. That’s not necessarily a bad thing, but we’d do well to bear it in mind. In this paper, Erik Nord sets out a kind of cost value analysis that does away with QALYs (gasp!). The author starts by outlining some familiar criticisms of the QALY approach, such as its failure to consider the inherent value of life and people’s differing reference points. Generally, I see these as features rather than bugs, and it isn’t QALYs themselves in the crosshairs here so much as cost-per-QALY analysis. The proposed method flips current practice by putting societal preferences about fair and efficient resource allocation before attaching values to the outcomes. As such, it acknowledges the fact that society’s preferences for gains in quality of life differ from those for gains in length of life. For example, society may prefer treating the more severely ill (independent of age) but also exhibit a ‘fair innings’ preference that is related to age. Thus, quality and quantity of life are disaggregated and the QALY is no more. A set of tables is presented that can be read to assess ‘value’ in alternative scenarios, given the assumptions set out in the paper. There is merit in the approach and a lot that I like about the possibilities of its use. But for me, the whole thing was made less attractive by the way it is presented in the paper. The author touts willingness to pay – for quality of life gains and for longevity gains – as the basis for value. Anything that makes resource allocation more dependent on willingness to pay values for things without a price (health, life) is a big no-no for me. But the method doesn’t depend on that. Furthermore, as is so often the case, most of the criticisms within relate to ways of using QALYs, rather than the fundamental basis for their estimation. This only weakens the argument for an alternative. But I can think of plenty of problems with QALYs, some of which might be addressed by this alternative approach. It’s unfortunate that the paper doesn’t outline how these more fundamental problems might be addressed. There may come a day when we do away with QALYs, and we may end up doing something similar to what’s outlined here, but we need to think harder about how this alternative is really better.



Transformative treatments: a big methodological challenge for health economics

Social scientists, especially economists, are concerned with causal inference: understanding whether and how an event causes a certain effect. Typically, we subscribe to the view that causal relations are reducible to sets of counterfactuals, and we use ever more sophisticated methods, such as instrumental variables and propensity score matching, to estimate these counterfactuals. Under the right set of assumptions, like that unobserved differences between study subjects are time invariant or that a treatment causes its effect through a certain mechanism, we can derive estimators for average treatment effects. All uncontroversial stuff indeed.

A recent paper from L.A. Paul and Kieran Healy introduces an argument of potential importance to how we can interpret studies investigating causal relations. In particular, they make the argument that we don’t know if individual preferences persist in a study through treatment. It is in general not possible to distinguish between the case where a treatment has satisfied an underlying revealed preference, or transformed an individual’s preferences. If preferences are changed or transformed, rather than revealed, then they are, in effect, a different population and in a causal inference type study, no longer comparable to the control population.

To quote their thought experiment:

Vampires: In the 21st century, vampires begin to populate North America. Psychologists decide to study the implications this could have for the human population. They put out a call for undergraduates to participate in a randomized controlled experiment, and recruit a local vampire with scientific interests. After securing the necessary permissions, they randomize and divide their population of undergraduates into a control group and a treatment group. At t1, members of each group are given standard psychological assessments measuring their preferences about vampires in general and about becoming a vampire in particular. Then members of the experimental group are bitten by the lab vampire.

Members of both groups are left to go about their daily lives for a period of time. At t2, they are assessed. Members of the control population do not report any difference in their preferences at t2. All members of the treated population, on the other hand, report living richer lives, enjoying rewarding new sensory experiences, and having a new sense of meaning at t2. As a result, they now uniformly report very strong pro-vampire preferences. (Some members of the treatment group also expressed pro-vampire preferences before the experiment, but these were a distinct minority.) In exit interviews, all treated subjects also testify that they have no desire to return to their previous condition.

Should our psychologists conclude that being bitten by a vampire somehow satisfies people’s underlying, previously unrecognized, preferences to become vampires? No. They should conclude that being bitten by a vampire causes you to become a vampire (and thus, to prefer being one). Being bitten by a vampire and then being satisfied with the result does not satisfy or reveal your underlying preference to be a vampire. Being bitten by a vampire transforms you: it changes your preferences in a deep and fundamental way, by replacing your underlying human preferences with vampire preferences, no matter what your previous preferences were.

In our latest journal round-up, I featured a paper that used German reunification in 1989 as a natural experiment to explore the impact of novel food items in the market on consumption and weight gain. The transformative treatments argument comes into play here. Did reunification reveal the preferences of East Germans for the novel food stuffs, or did it change their preferences for foodstuffs overall due to the significant cultural change? If the latter case is true then West Germans do not constitute an appropriate control group. The causal mechanism at play is also important to the development of policy: for example, without reunification there may not have been any impact from novel food products.

This argument is also sometimes skirted around with regards to the valuing of health states. Should it be the preferences of healthy people, or the experienced utility of sick people, that determine health state values? Do physical trauma and disease reveal our underlying preferences for different health states, or do they transform us to have different preferences entirely? Any study looking at the effect of disease on health status or quality of life could not distinguish between the two. Yet the two cases are akin to using the same or different groups of people to do the valuation of health states.

Consider also something like estimating the impact of retirement on health and quality of life. If self-reported quality of life is observed to improve in one of these studies, we don’t know if that is because retirement has satisfied a pre-existing preference for the retired lifestyle, or retirement has transformed a person’s preferences. In the latter case, the appropriate control group to evaluate the causal effect of retirement is not non-retired persons.

Paul and Healy do not make their argument to try to prevent or undermine research in the social sciences, they interpret their conclusion as a “methodological challenge”. The full implications of the above arguments have not been explored but could be potentially great and new innovations in methodology to estimate average causal effects could be warranted. How this may be achieved, I’ll have to admit, I do not know.


Paul Mitchell’s journal round-up for 2nd January 2017

Every Monday our authors provide a round-up of some of the most recently published peer reviewed articles from the field. We don’t cover everything, or even what’s most important – just a few papers that have interested the author. Visit our Resources page for links to more journals or follow the HealthEconBot. If you’d like to write one of our weekly journal round-ups, get in touch.

Age effects in mortality risk valuation. European Journal of Health Economics [PubMed] [RePEcPublished 7th December 2016

Placing values on statistical life years has important public policy implications in measuring who benefits and how much they benefit from interventions. The authors of this study provide what they describe as the most comprehensive evidence to date against a constant value for a statistical life year, an assumption they argue is also applicable when calculating QALYs. Using a Spanish household survey collected over a large sample size (approximately 6,000 individuals), the authors study the relationship between willingness to pay (WTP) and age, by estimating individual WTP for reduction in risk of mortality due to acute myocardial infarction. Three different WTP elicitation procedures were performed. Parametric, semi-nonparametric and non-parametric models using marginal and total approaches were applied to understand the relationship using many alternative methods. Binary variables for income (proxied on a measure of self-perceived social status), education (>lower secondary level) and gender were also included as controls for the models. The results of the linear model show that WTP is lower as age increases. Those with higher income (i.e. social status) and education have higher WTP, while gender is not significant in any model. Sensitivity tests were as hypothesised. The non-parametric model produces similar results to the others, albeit with a higher senior discount. The senior discount is not independent of the income variable. From this, the authors estimate the value of a statistical life year for an 85 year old to be 3.5 times higher than that of a 20 year old. The authors are keen to highlight the strengths of their findings with a large sample size allowing for the robustness of results to be tested across a number of different model types. However, they do flag up the lack of comparability with previous studies that have focused on risk reductions with a lower probability of mortality. The assumption that the authors make that their findings for life years have direct applicability for QALYs is somewhat questionable, particularly for non-acute conditions and QALYs calculated for them. The rationale behind the three types of preference elicitation methods and how/why they were chosen is not apparent in the paper itself. The social status measure they use as a proxy for income is also questionable, and appeared to be applied to maximise sample size. If data for real income was used or imputation of income was included for missing data, it would be interesting to see what impact this may have had on their study findings.

Preferences for public involvement in health service decisions: a comparison between best-worst scaling and trio-wise stated preference elicitation techniques. European Journal of Health Economics [PubMedPublished 10th December 2016

Public involvement in health care is something that has become increasingly recognised as important to do and to be informed by public perspectives when making important decisions for their community. How and where that public involvement should feed into decision making is less well understood. In this study, the authors compare two methods, best worst scaling (BWS) case 2, and a new method the authors call ‘trio-wise’ where the choice task is presented in an equilateral triangle. Using ‘trio-wise’, respondents are able to click in any part of the triangle; this the authors argue gives additional insight on the strength of a respondent’s preferences and also accommodates indifferent preferences. Public preferences are sought using these two methods to understand what aspects of public involvement are most important. Eight general characteristics are included in the exercises. Respondents completed either BWS or the ‘trio-wise’ task (not both) using web based surveys. Approximately 1,700 individuals per arm were sampled. Only three of the eight general characteristics could be completed at any one time due to the trio-wise triangle approach. There was some evidence of position bias for both exercises. The authors say that weak preferences were observed using the trio-wise approach but this could be due to difficulty participants faced in choosing which generic characteristic was more important without further information. Impact and focus of public involvement are found to be the most important characteristics across both BWS and trio-wise. The authors find preference intensity has no bearing on choice probabilities, but this could be an artefact of the weak preferences observed in the sample. Although I can see the appeal of using the trio-wise approach when there are only three characteristics, BWS is advantageous in tasks with more characteristics. Indeed it feels that the findings from this experiment were impeded by the use of the trio-wise approach when much more useful information on guiding future public involvement practice could have been gathered using either BWS or a discrete choice experiment (DCE) across all eight characteristics and the options of public involvement within each characteristic.

How do individuals value health states? A qualitative investigation. Social Science & Medicine [PubMedPublished 22nd November 2016

The valuation tasks of health states used to generate QALYs have been previously found to be complex tasks for members of the general public to complete, who have little experience of such health states. This qualitative study seeks to gain a better understanding as to how the general public complete such tasks. Using a purposive sample, 21 individuals were asked to complete eight DCEs and three TTO tasks, based on the EQ-5D-5L valuation protocol. Participants were asked to complete the valuation tasks using think aloud, followed by semi-structured interviews. Three main themes emerged from the framework analysis undertaken on the interview transcripts. Firstly, individuals had to interpret a health state, using their imagination and experience to help visualise a realistic health state with those problems. Knowledge, understanding of descriptive system, additional information for a health state, re-writing of health states and problems with EQ-5D labels all impacted this process. The second theme was called conversion factors, which the authors took to mean in this context the personal and social factors that affected how participants valued health states. Personal interests, values and circumstances were said to have an effect on the interpretation of a health state. The final theme was based on the consequences of health states, that tended to focus on non-health effects caused by health problems, such as activities, enjoyment, independence, relationships, dignity and avoiding being a burden. The authors subsequently developed a three-stage explanatory account as to how people valued health states based on the interview findings. Although I would have some concerns about the generalisability of these findings to general public valuation studies, given the highly educated sample, it does highlight some issues about what health economists might implicitly think individuals are doing when completing such tasks compared to what they actually are doing. There are clearly problems for individuals completing such hypothetical health states, with the authors suggesting a more reflective and deliberative approach to overcome such problems. The authors also raise an interesting comment as to whether participants actually do weigh the consequences of health states and follow compensatory decision-making or instead are using simplifying heuristics based on one attribute, which I agree is an area that requires further investigation.