The objective of the study was to understand respondents' willingness to accept hypothetical treatment-related risks in return for the benefit of additional time with normal memory from potential Alzheimer's disease interception therapies.
A US web-based discrete-choice survey was administered to respondents ages 60 to 85 years with no Alzheimer's disease diagnosis and no cognitive symptoms. Choice questions required respondents to indicate whether they preferred a constant, no-treatment condition described as 4 years of normal memory followed by 3 years of cognitive impairment and 5 years of dementia or an interception treatment with chosen risks of disabling stroke and death, but with increased duration of normal memory. The study design included internal validity tests to verify data quality.
On average, respondents were willing to accept a 5% to 13% risk of stroke or death in the first year for treatments that could provide 1 or more additional years with normal memory. Nevertheless, 30% of respondents failed a simple internal-validity test question where the treatment alternative offered no improvement in disease progression but had significant side effects. These respondents also were more likely to choose active treatment in the subsequent series of choice questions. This unexpected finding is consistent with hopeful attitudes of patients with debilitating and potentially fatal conditions.
Pro-treatment attitudes are clinically relevant and can affect the analysis and interpretation of stated-preference data. Internal-validity tests generally are underutilized in preference research. This study demonstrated how analysis of apparent validity failures can yield important insights about patient preferences.