The concept of adaptation has been offered to explain prior reports that individual health valuations deviate from societal valuations in chronic disease patients, yet psychological characteristics indexing this adaptational capacity35
We investigated the effect of personality on a measure of individual deviation from societal valuations of a particular health state, Dev
After controlling for a number of potential confounds, chronically ill patients with levels of conscientiousness in the middle 2 quartiles place greater value on their health than normative based societal preferences would suggest. These effects were more than 4 times the effect of most chronic conditions31
and exceed most thresholds for clinical significance, as did the trend for the highest quartile. The conscientiousness effect was the only significant systemic effect observed among all the covariates apart from that associated with self-reported depression; the conscientiousness effect was approximately twice that of self-reported depression. These considerations suggest that persons of higher conscientiousness experience less disutility at poor health states, at a clinically meaningful level. The effects of conscientiousness, neuroticism, and extraversion on the EQ-5D and VAS were larger even than their effect on Dev, also suggesting the importance of personality for both personal and societal preference scores.
Why more conscientious individuals valuate their particular health state more highly than do societal norms? Persons higher in conscientiousness are more goal-oriented and self-controlled,27
adherent to medical treatment,37
invested in adopting healthful behaviors,38
cautious in their estimation of health risks,39-41
less likely to self-handicap42
or report hypochondriacal symptoms.43,44
Such individuals also have less medically documented illness burden45
and lower all-cause mortality risk.46
Thus conscientiousness may be associated with Dev
due to thought, perception, and health status itself.
In secondary analyses, higher conscientiousness also affected VAS scores. Neuroticism was associated with worse absolute health status on both measures. However the individual health evaluations made by more neurotic patients were not appreciably worse than those based on societal norms, because such patients report poor health comparably across measures. These analyses also suggest that personality may affect the EQ-5D directly.
One implication of this finding is that because adaptation is connected to specific personality tendencies, preference-based measures may systematically undervalue the health of individuals with those tendencies. Time trade-off or standard gambles inspired by the framework of von Neumann and Morgenstern and used for health state valuations essentially rely on personal preferences, and thus may be inherently tied to personality effects. However, to gauge whether cost-effectiveness analysis of clinical studies produce less meaningful utility estimates for certain types of patient groups such as the conscientious, study of under- or over-valuation of change in health status is required. If links between Dev and factors such as personality can be elucidated, they can be explicitly incorporated into analyses employing societal preference-weighted health status measures, potentially improving their validity and applicability to individuals.
Findings must be interpreted in light of balanced assessment of study strengths and limitations. Although the focus on chronic disease patients was strength, it also represents the limiting frame of generalizability. Also, the decision to participate in a research study is likely affected by the personality profile of the potential subject, and involved a particular geographic area and chronic conditions. Future work might investigate this phenomenon in other regions and patient groups. The measures we used were among the most common, however, maximizing relevance of the study. To the extent that the EQ-5D is informed by individual as well as societal preferences, it is likely that the Dev
under-estimates the true difference between personal and societal valuations of a given health state. Additionally, the EQ-5D is based on time trade-off, while the EQ-VAS is not, and/or may incorporate health information not reflected in the EQ-5D. However, this is a common issue,34,47
and findings proved robust in sensitivity analyses with a power transformation approximating the time trade-off distribution. Finally, Dev
should be investigated in the context of specific chronic diseases, and outside the context of chronic disease management programs.
In conclusion, conscientiousness appears to be the personality factor responsible for differences between individual and societal valuations of health status. Controlling for other relevant factors, persons of greater conscientiousness report less disutility from poor health states than the societal valuations of these health states used in reference case analysis. Future consideration of the role of personality in outcome evaluation of patients in clinical research studies appears warranted.