The results of this study illustrate that for some older, seriously ill persons, changes in their health are associated with changes in their valuations of the outcomes that may result from treatment for their illness. Those patients who experienced a decline in instrumental activities of daily living were more likely to rate more severe functional disability as an acceptable outcome of therapy than those who do not experience such a decline. Similarly, those who experienced moderate or severe pain were more likely to rate severe pain as an acceptable outcome of therapy than those who experienced no or mild pain. Changes in the valuations of health states resulting from treatment are specific to the state itself. Even after accounting for changes in functional status as well as sociodemographic and other health and psychosocial characteristics, the acceptability of functional disability increased over time, whereas the acceptability of severe cognitive impairment decreased. However, in absolute terms, the majority of participants did not change their ratings of the acceptability of these health states.
Although this study focused on eliciting patients' valuations of health states, it assessed these valuations in the context of whether the patient would choose to have therapy resulting in the given health state. The majority of previous studies have examined the relationship between clinical status and preferences for specific treatment interventions. Several of these studies demonstrate a relationship between declining health and a greater likelihood of a preference for high-burden life-sustaining treatment.12,18
These studies suggest that declining health status is associated with a greater willingness to bear the burdens of therapy. By systematically evaluating the attitudes of older persons facing a decline in their health toward a variety of health states, this study suggests that an increased desire to undergo therapy results, at least in part, from the willingness to tolerate diminished states of health, a finding that confirms previous studies.34, 35
These findings are consistent with the theory of “response shift,” whereby patients change their self-evaluation of quality of life with changes in their health status.36
This concept is further supported by the finding that higher self-rated quality of life, independent of pain, function, or other markers of health, was associated with a greater likelihood of rating several of the health states as acceptable.
The results of this study pose a serious challenge to the instructional form of advance care planning. The main purpose of these instructions is to allow patients to express their preferences for care in the case of future circumstances in which they are unable to speak for themselves. This presupposes that patients' projections of the treatment they want for themselves in some future state accurately reflect how they would actually feel in that state. However, the findings of this study illustrate that some patients cannot accurately predict their future valuations. This limitation is well recognized in certain fields, such as psychology37
but it has not been a prominent part of considerations regarding advance care planning.
The problems with predicting future hypothetical states of health have led some to conclude that instructional advance directives are a misguided means of care planning.39
However, the methods we used to demonstrate the problem of predicting future health states provide a partial solution to the problem Many patients were still able to think about and express their preferences regarding these states after experiencing a change in their health status. This finding implies that, if advance care planning is conducted as a process over time, in which patients are asked to reflect on their preferences after experiencing a change in their health, they will have the opportunity to reflect upon how their preferences may be changing. In addition, the appointment of a health care proxy, another form of advance care planning, is not dependent upon patients' ability to predict future states of health. The finding of changes in preferences supports the notion of allowing surrogates leeway in the interpretation of advance directives, an approach that is endorsed by a large majority of patients.40, 41
Because the study examined the preferences of patients with advanced illness, missing data are unavoidable. The largest cause of missing data in the study was mortality. It is unclear if these data are “missing” in the sense that this term is traditionally used, since these data, along with the data from participants who became cognitively impaired or more acutely ill, are not recoverable. However, there were also missing data from participants who dropped out of the study for other reasons or who failed to consent to a second year of participation. The issue of missing data in longitudinal research is one of current investigation, and there are no easy or straightforward methods for assessing the impact of missing data. Therefore, we cannot know whether these missing data introduce some bias into the results. Nonetheless, the high overall rates of participation and completeness of data collection among patients who remained in the study suggest that data collection was as complete as possible in this challenging population.
The study population included only a small number of non-white participants. Because there was a trend for non-white race to be associated with ratings of the acceptability of health states, the findings of this study regarding the rates of different trajectories of health state ratings may not be applicable to all populations of older persons with advanced chronic illness. Further, this study leaves unanswered the important question of the reason(s) why valuations of health states change over time.42
Nonetheless, the changes in older persons' treatment preferences over time and the association between changes in older persons' health and treatment preferences highlight the need for repeated assessments of these preferences.