Desire for predictive testing for Alzheimer’s disease and impact on advance care planning: a cross-sectional study
In this nationally representative study of 874 community-dwelling older adults, 75% were interested in a hypothetical test that would predict development of Alzheimer’s disease in the future. This high desire did not differ by sex, race, functional status, comorbidity, perceived memory, or perceived risk of Alzheimer’s disease. Additionally, in the face of a positive test, 87% reported they would be likely to discuss health plans with loved ones, and 81% reported they would be likely to complete an advance directive.
This degree of public interest in predictive testing for dementia is similar to what has been seen in several prior online and telephone studies with nonrandom samples [2, 4, 5, 14]. In a 2014 online survey of subjects enrolled in an online community interested in Alzheimer’s disease prevention research [4], 81% wanted genetic testing for Alzheimer’s disease if paid by insurance, and 70% thought genetic testing was important even in the absence of any effective intervention. In a telephone survey of 2678 subjects across five countries done in 2013 [2], 67% of all subjects stated they would be somewhat or very likely to obtain testing if it was available in the future. In an additional analysis, knowing Alzheimer’s disease is a fatal condition did not affect the results. In related work, Roberts [15] used nationally representative data from the 2010 HRS to assess to what degree individuals aged 50 years and older wanted to know their chances of developing Alzheimer’s disease. They found that 60% of respondents age 50 years and older endorsed “somewhat” or “strong” agreement with the desire to know their future chances of getting this disease. While there are substantial differences between a general interest in risk and willingness to take a fully predictive test, these results are generally consistent with our findings.
Two prior studies of predictive testing for Alzheimer’s disease asked questions regarding advance directives. In a small 2001 study asking a question similar to our own, out of 314 US adults responding to a random-digit-dialed telephone survey, 79% of would take a hypothetical perfect genetic test for Alzheimer’s disease [14]. Additionally, 84% stated that signing an advance directive was one of the actions they would take after a positive result. In a 2012 online survey of 772 respondents enrolled in a national online panel of US residents, 70–75% would take a test predictive for Alzheimer’s disease [5], and 51% would sign an advance directive document if receiving a positive test.
These studies of subjects with high interest in Alzheimer’s disease and responders to telephone and Internet surveys found similar results to those presented here. We found similar high interest in predictive testing for Alzheimer’s disease and intention to complete advance directives in our nationally representative sample of community-dwelling older adults. Our findings add to this existing body of knowledge in several important ways. Using a nationally representative sample helps to overcome the limitations of smaller or more selected samples, and confirms the high public concern and worry about Alzheimer’s disease as found in a prior study using the HRS [15]. The HRS is much less affected by response bias, utilizing careful weighting procedures to account for interview nonresponse. Additionally, our ability to evaluate a variety of potential predictors of attitudes toward testing helps to shed light on the factors that influence desire for predictive testing.
We did not find clinically meaningful differences in desire for predictive testing by level of comorbidity or disability, age, or perceived risk of Alzheimer’s disease. While somewhat surprising, if an individual’s threshold for testing is very low, patient characteristics may not affect the desire for testing and overall interest will be high.
Additionally, high interest in testing may reflect increasing media attention to the topic of dementia. There may be a general lack of knowledge of available treatments for dementia, perception that they are more effective than they actually are, or the hope that a treatment or cure will soon be available. This is supported by prior work which found that 40% of those surveyed thought prescription drugs that prevent Alzheimer’s disease are currently available [15]. Additionally, many believed there were behaviors that could be protective against Alzheimer’s disease, with 40% stating keeping physically active would be helpful and 20% believing taking vitamins/herbal supplements would help [15]. These beliefs may account for high interest in testing among all groups of respondents. Subjects may also desire predictive testing to aid in preparing family members for the development of Alzheimer’s disease [16].
Understanding the potential demand for predictive testing for Alzheimer’s disease may guide implementation of availability and use of these tests when they do become widely available. Disadvantages of large-scale predictive testing must be considered, including the false positives and need for education or counseling to assist patients in interpreting the results. Possible harms of predictive testing for Alzheimer’s disease could potentially include excess worry, employment discrimination, and ineligibility for long-term care insurance, among others. These possible harms of testing must be considered, especially given the current lack of effective prevention and the fatal nature of dementia. However, engaging patients who present to a physician seeking predictive testing for Alzheimer’s disease could be a unique opportunity to discuss advance care planning with older adults. This would allow them to make choices and express wishes for future care before they became cognitively impaired, and to initiate the conversation. Advance care planning is a process [17] and predictive testing for dementia may be an additional moment in which physicians can guide patients in the steps of determining, sharing, and documenting their values and preferences.
Our study does have some limitations. The question stem did not clearly include information on the progressive nature of Alzheimer’s disease or lack of very effective treatments, and it is possible that some subjects did not have this knowledge. However, there is increasing attention on Alzheimer’s disease in the media, and subjects may still be interested in a test because they have hope for future treatments or will use it to plan their future. We must note that the study question asked a hypothetical question about a free and definitive test for Alzheimer’s disease. A perfectly predictive test does not exist; all tests will have some rate of false positives and false negatives and no test is ever likely to be truly definitive. However, patients often assume tests are perfect and will yield definitive results, even when that is not the case. A clear and concise hypothetical question can be useful to assess the underlying preferences of the public regarding testing for Alzheimer’s disease in general; those underlying preferences would be modified based on the nuances, test characteristics, and cost of whatever test becomes available.
The expressed high desire for taking a hypothetical predictive test for Alzheimer’s disease may overestimate the demand for these tests once they are available, because people may not act on their current wishes. Studies of predictive testing for Huntington’s disease predicted uptake of 50–80%, although actual uptake was lower when testing was developed [6]. This may be due to more fears of stigmatization and genetic discrimination associated with Huntington’s disease [6], although there are more legal protections for the latter in recent years. Despite this, the high interest found by our study and others suggest that even if the percentage of subjects seeking testing is much lower, there will still be a substantial demand for predictive tests for Alzheimer’s disease. True levels of advance care planning may also be lower than what subjects reported they intend to do. However, the current rate of advance directive completion found in our study (15%) is very low, and discussing advance care planning with patients seeking predictive testing for Alzheimer’s disease is an opportunity to substantially improve the rates of discussions of advance care planning and completion of advance directives. Finally, the question stem describes a hypothetical free and definitive test predictive of Alzheimer’s disease, and some may argue that this will never exist. While a test is unlikely to be 100% definitive, research is being conducted to find a predictive test that is both highly sensitive and specific. Additionally, if the cost of testing is paid by insurers it may be provided to patients at low to no cost, and may seem “free” to them.