Population-based time preferences for future health outcomes

Private and social time preference for health outcomes: A general population survey in Iran

Despite the recent increase in economic evaluations of health care programs in low and middle income countries, there is still a surprising gap in evidence on the appropriate discount rate and the discounting of health outcomes such as quality adjusted life years (QALYs). Our study aimed to calculate the implied time preference rate for health outcomes in Iran and its key determinants. Data were gathered from one family member from each of the 650 households randomly selected in Tehran. The respondents’ private and social preferences for health outcomes were calculated using the time trade-off (TTO) technique based on the discounted utility model. We investigated the main assumptions of the discounted utility model through equality of mean comparison, and the association between private time preference and key socio-economic determinants using multilevel regression analysis. The mean and median implied rates were 5.8% and 4.9% for private time preference and 25.6% and 20% for social time preference respectively. Our study confirmed that magnitude, framing and time effects have a significant impact on implied discount rates, which means that the conventional discounted utility model’s main assumptions are violated in the Iranian general population. Other models of discounting which apply lower rates for far health outcomes might provide a more sensible solution to discounting health interventions with long-term impacts.

Observed and Normative Discount Functions in Addiction and other Diseases

The aim of this paper is to find a suitable discount function able to describe the progression of a certain addiction or disease under treatment as a discounting process. In effect, a certain indicator related to a disease decays over time in a manner which is mathematically similar to the way in which discounting has been modeled. We analyze the discount functions observed in experiments which study addictive and other problematic behaviors as well as some alternative hyperbola-like discount functions in order to fit the patience exhibited by the subject after receiving the treatment. Additionally, it has been experimentally found that people with addiction display high rates of discount (impatience) and preference reversals (dynamic inconsistency). This excessive discounting must be correctly modeled by a suitable discount function, otherwise, it can become a trans-disease process underlying addiction and other disorders. The (generalized) exponentiated hyperbolic discount function is proposed to describe the progression of a disease with respect to the treatment, since it maintains the property of inconsistency by exhibiting a decreasing discount rate after an initial period in which the opposite occurs.

Time discounting and smoking behavior: evidence from a panel survey(*)

By using a panel survey of Japanese adults, we show that smoking behavior is associated with personal time discounting and its biases, such as hyperbolic discounting and the sign effect, in the way that theory predicts: smoking depends positively on the discount rate and the degree of hyperbolic discounting and negatively on the presence of the sign effect. Positive effects of hyperbolic discounting on smoking are salient for naïve people, who are not aware of their self-control problem. By estimating smoking participation and smokers' cigarette consumption in Cragg's two-part model, we find that the two smoking decisions depend on different sets of time-discounting variables. Particularly, smoking participation is affected by being a naïve hyperbolic discounter, whereas the discount rate, the presence of the sign effect, and a hyperbolic discounting proxy constructed from procrastination behavior vis-à-vis doing homework assignments affect both types of decision making. The panel data enable us to analyze the over-time instability of elicited discount rates. The instability is shown to come from measurement errors, rather than preference shocks on time preference. Several evidences indicate that the detected associations between time preferences and smoking behavior are interpersonal one, rather than within-personal one.

Does temporal discounting explain unhealthy behavior? A systematic review and reinforcement learning perspective

The tendency to make unhealthy choices is hypothesized to be related to an individual's temporal discount rate, the theoretical rate at which they devalue delayed rewards. Furthermore, a particular form of temporal discounting, hyperbolic discounting, has been proposed to explain why unhealthy behavior can occur despite healthy intentions. We examine these two hypotheses in turn. We first systematically review studies which investigate whether discount rates can predict unhealthy behavior. These studies reveal that high discount rates for money (and in some instances food or drug rewards) are associated with several unhealthy behaviors and markers of health status, establishing discounting as a promising predictive measure. We secondly examine whether intention-incongruent unhealthy actions are consistent with hyperbolic discounting. We conclude that intention-incongruent actions are often triggered by environmental cues or changes in motivational state, whose effects are not parameterized by hyperbolic discounting. We propose a framework for understanding these state-based effects in terms of the interplay of two distinct reinforcement learning mechanisms: a “model-based” (or goal-directed) system and a “model-free” (or habitual) system. Under this framework, while discounting of delayed health may contribute to the initiation of unhealthy behavior, with repetition, many unhealthy behaviors become habitual; if health goals then change, habitual behavior can still arise in response to environmental cues. We propose that the burgeoning development of computational models of these processes will permit further identification of health decision-making phenotypes.

Methods for Performing Survival Curve Quality-of-Life Assessments

BACKGROUND

Many medical decisions involve an implied choice between alternative survival curves, typically with differing quality of life. Common preference assessment methods neglect this structure, creating some risk of distortions.

METHODS

Survival curve quality-of-life assessments (SQLA) were developed from Gompertz survival curves fitting the general population's survival. An algorithm was developed to generate relative discount rate-utility (DRU) functions from a standard survival curve and health state and an equally attractive alternative curve and state. A least means squared distance algorithm was developed to describe how nearly 3 or more DRU functions intersect. These techniques were implemented in a program called X-Trade and tested.

RESULTS

SQLA scenarios can portray realistic treatment choices. A side effect scenario portrays one prototypical choice, to extend life while experiencing some loss, such as an amputation. A risky treatment scenario portrays procedures with an initial mortality risk. A time trade scenario mimics conventional time tradeoffs. Each SQLA scenario yields DRU functions with distinctive shapes, such as sigmoid curves or vertical lines. One SQLA can imply a discount rate or utility if the other value is known and both values are temporally stable. Two SQLA exercises imply a unique discount rate and utility if the inferred DRU functions intersect. Three or more SQLA results can quantify uncertainty or inconsistency in discount rate and utility estimates. Pilot studies suggested that many subjects could learn to interpret survival curves and do SQLA.

LIMITATIONS

SQLA confuse some people. Compared with SQLA, standard gambles quantify very low utilities more easily, and time tradeoffs are simpler for high utilities. When discount rates approach zero, time tradeoffs are as informative and easier to do than SQLA.

CONCLUSIONS

SQLA may complement conventional utility assessment methods.

Would you rather be ill now, or later?

The time tradeoff (TTO) method is frequently used to calculate the quality adjustment of the quality adjusted life year and is therefore an important element in the calculation of the benefits of medical interventions. New specifications of TTO, known as 'lead time' TTO and 'lag time' TTO, have been developed to overcome methodological issues of the 'classic' TTO. In the lead time TTO, ill-health is explicitly placed in the future, after a period of good health, whereas in lag time TTO, a health state starts immediately and is followed by a 'lag time' of good health. In this study, we take advantage of these timing properties of lead and lag time TTO. In particular, we use data from a previous study that employed lead and lag time TTO to estimate their implied discounting parameters. We show that individuals prefer being ill later, rather than now, with larger per-period discount rates for longer durations of the health states.

A direct method for measuring discounting and QALYs more easily and reliably

Time discounting and quality of life are two important factors in evaluations of medical interventions. The measurement of these two factors is complicated because they interact. Existing methods either simply assume one factor given, based on heuristic assumptions, or invoke complicating extraneous factors, such as risk, that generate extra biases. The authors introduce a method for measuring discounting (and then quality of life) that involves no extraneous factors and that avoids distorting interactions. Their method is considerably simpler and more realistic for subjects than existing methods. It is entirely choice based and thus can be founded on economic rationality requirements. An experiment demonstrates the feasibility of this method and its advantages over classical methods.

The welfare costs of HIV/AIDS in eastern Europe: an empirical assessment using the economic value-of-life approach

Based on the aggregation of individual willingness-to-pay for a statistical life, we calibrate an inter-temporal optimisation model to determine the aggregate welfare loss from HIV/AIDS in 25 Eastern European countries. Assuming a discount rate of 3%, we find a total welfare loss for the whole region that exceeds US $800 billion, approximately 10% of the region's annual GDP between 1995 and 2001. Although prevalence and incidence rates diverge sharply between countries-with central Europe far less affected than major countries in the Commonwealth of Independent States and the Baltics-the epidemic is likely to spread to all countries unless a coherent strategy of prevention and treatment is backed up by substantial increases in healthcare investments. The sheer size of this task and the international nature of the epidemic render this one of the most important current challenges for all of Europe.

A low tension between individual and societal time aspects in health improved outcomes

OBJECTIVES

To review intertemporal choices, involving decisions with a trade-off between something now and something later. These choices are common in health both at an individual and societal level.

METHODS

The present value of an outcome, for example, the amount of money or the health outcomes in various aspects, is equivalent to the value of a future outcome discounted with the delay of time. The concept of diminishing value over time is positive discounting. Economic forecasts generally use discount rates in which the value of a future dollar is less than the value of a present dollar, and where the discount rates are similar for the individual investor and society. The value of future health is commonly thought of as similar to the value of future money. Yet, the individual may rationally choose a discount rate that is exceedingly low or even negative. This paradox is particularly relevant when considering primary and secondary prevention, where initial and continuing costs may precede beneficent outcomes by decades, making discount rate selections the dominant factor in determining decisions.

CONCLUSION

We suggest that the societal perspective should also recognize that discount rates for health outcomes are largely irrelevant and that even negative discount rates have crucial relevance.

Time preference bias in time trade-off

This study examined whether time trade-off (TTO) values adjusted for time preferences are more consistent with individuals' preferences. This was carried out by testing the constant proportional trade-off (CPTO) assumption, and both individual specific and standard discount rates were used. The results show that the mean adjustment factor is around 0.03. This may influence relative cost-effectiveness in economic evaluations. The CPTO assumption holds with respect to both unadjusted TTO values and TTO values adjusted for individuals'time preference, and therefore no conclusions can be drawn as to whether the adjusted values are more consistent with individuals' preferences. However, the CPTO assumption is violated when standard discount rates are used. This clearly shows that the use of standard discount rates should be avoided. Further exploration of the time preference bias and other biases in TTO is identified as an important area of future research.

Health-state valuations for pertussis: methods for valuing short-term health states

BACKGROUND

The incidence of reported adolescent and adult pertussis continues to rise in the United States. Acellular pertussis vaccines for adolescents and adults have been developed and may be available soon for use in the U.S. Our objectives were: (1) to describe patient valuations of pertussis disease and vaccination; and (2) to compare valuations for short-term and long-term health states associated with pertussis.

METHODS

We conducted telephone surveys with 515 adult patients and parents of adolescent patients with pertussis in Massachusetts to determine valuations of pertussis-related health states for disease and vaccination using time trade-off (TTO) and contingent valuation (CV) techniques. Respondents were randomized to complete either a short-term or long-term TTO exercise. Discrimination between health states for each valuation technique was assessed using Tukey's method, and valuations for short-term vs. long-term health states were compared using the Wilcoxon rank-sum test.

RESULTS

Three hundred three (59%) and 309 (60%) respondents completed and understood the TTO and CV exercises, respectively. Overall, respondents gave lower valuations (lower TTO and higher CV values) to avoid a given state for adolescent/adult disease compared to vaccine adverse events. Infant complications due to pertussis were considered worse than adolescent/adult disease, regardless of the method of valuation. The short-term TTO resulted in lower mean valuations and larger mean differences between health states than the long-term TTO exercise.

CONCLUSION

Pertussis was considered worse than adverse events due to vaccination. Short-term health-state valuation is better able to discriminate among health states, which is useful for cost-utility analysis.

Controlling Blood Pressure in 50% of All Hypertensive Patients: An Achievable Goal in the Healthy People 2010 Report?

Background

One important objective defined in the Healthy People 2010 report was to improve blood pressure (BP) control to < 140/90 mm Hg in 50% of all hypertensive patients. Because the US population is becoming older, more obese, and ethnically diverse, the health and economic benefits of reaching this goal become more valuable each year. Hypertension control rates are currently at ∼ 31% of all hypertensives and have risen slowly and erratically since 1988. In the absence of a coordinated strategic plan, achieving this critically important goal for BP control is highly unlikely.

Methods

A selected literature review was undertaken to briefly assess the cardiovascular benefits of controlling hypertension. Greater focus was placed on variables that impact hypertension awareness, treatment, and control. The impact on hypertension control rates of theoretic changes in awareness, treatment, and control individually and collectively was examined. Four categories of potential barriers to optimizing BP control are discussed: systems, provider, patient, and treatment factors.

Results

Raising awareness to 80% of all hypertensives, ensuring treatment of 90% of aware hypertensives, and controlling BP to < 140/90 mm Hg in 70% of treated patients would achieve control rates of 50%.

Conclusions

The barriers to achieving the Healthy People 2010 goal of controlling hypertension in 50% of all patients are formidable but appear to be resolvable with a coordinated strategic plan. Given projected demographic changes in the United States, the health and economic benefits of attaining the national goal for hypertension control would seem to merit a serious integrated effort.

Time perspective predicts the progression of permanent organ damage in patients with systemic lupus erythematosus

Patients whose perspective is oriented to the future more than to the present may have better long-term health outcomes. We examined if time perspective predicted future organ damage in patients with systemic lupus erythematosus (SLE). We assessed the time perspectives of 87 patients with SLE using a questionnaire at a baseline visit. Permanent organ damage was assessed by the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index during the same visit, and reassessed after a median of 4.6 years. Patients who were oriented more to the future were less likely to have an increase in the Damage Index than those oriented more to the present. In a multivariate analysis, each 1-point increase in the degree of orientation to the future (on a scale of 1-6) was associated with a 22% decrease in the likelihood that the Damage Index would increase over time (odds ratio 0.78; 95% confidence interval 0.64-0.94; P = 0.009). Other measures that predicted an increase in the Damage Index were lower education levels, greater health locus of control attributed to chance and greater health locus of control attributed to powerful others. In conclusion, time perspective is a significant predictor of future organ damage in SLE. Patients who have a greater orientation to the future are less likely to develop permanent organ damage.

Effects of systematic asymmetric discounting on physician-patient interactions: a theoretical framework to explain poor compliance with lifestyle counseling

BACKGROUND

This study advances the use of a utility model to model physician-patient interactions from the perspectives of physicians and patients.

PRESENTATION OF THE HYPOTHESIS

In cases involving acute care, patient counseling involves a relatively straightforward transfer of information from the physician to a patient. The patient has less information than the physician on the impact the condition and its treatment have on utility. In decisions involving lifestyle changes, the patient may have more information than the physician on his/her utility of consumption; moreover, differences in discounting future health may contribute significantly to differences between patients' preferences and physicians' recommendations.

TESTING THE HYPOTHESIS

The expectation of differences in internal discount rate between patients and their physicians is discussed.

IMPLICATIONS OF THE HYPOTHESIS

This utility model provides a conceptual basis for the finding that educational approaches alone may not effect changes in patient behavior and suggests other economic variables that could be targeted in the attempt to produce healthier behavior.

Association of time preference for health with age and disease severity

This study assessed the relationship between time preference for health and age and disease severity. An implicit time preference for health was inferred in 59 patients with chronic obstructive pulmonary disease (COPD) using the time tradeoff method with 10-year and 30-year perspectives. The preference rate was calculated by solving the resulting nonlinear equation, solvable for 50 patients.Among the resulting rates, 4 were negative, 8 zero, and 38 positive. The time preference rate ranged from -10.8% to 75.0%, with a median of 6.6%, and a mean of 11.5%. In correlation analysis, the implicit time preference rate was associated with age;however, there was little association with markers of disease severity. In multivariate analysis, only age was a significant predictor of time preference rate after controlling for the other variables in the model.

Theoretical arguments for the discounting of health consequences: where do we go from here?

Despite the theoretical arguments presented in the literature regarding discounting over the last 25 years, no satisfactory reply has yet been offered to the question of whether health consequences have to be discounted at the same rate as monetary consequences in the economic evaluation of health programmes or interventions designed to improve health. Against this background, the main objective of this paper was to review and systemise these theoretical arguments, with the aim of determining whether any of the positions identified can be accepted without reservation. Having determined that this is not possible, we investigated the rationality of discounting in the literature and, on this basis, propose a potential way to resolve the problem. Thus, we argue that the relationship between the discount of monetary and health consequences has to be determined in an indirect manner, by reference to the relationship maintained by the individual time preference rates for health and money in the context of private and social choice. Although this proposal moves the debate into the empirical field, its advantages must be weighed against the difficulties associated with the estimation of the time preferences.