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From the Department of Psychology (O.C.O.), Department of Neurology (H.R.G., J.N.C., K.B., S.L., L.E.H., J.C.B., D.C., D.C.M.), and Alzheimer’s Disease Research Center (H.R.G., J.N.C., K.B., S.L., L.E.H., J.C.B., D.C., D.C.M.), University of Alabama at Birmingham, AL; Veterans Administration Medical Center (L.E.H., D.C.), Birmingham, AL; Department of Neurology (E.Y.Z.), University of Utah Health Sciences, Salt Lake City, UT; Dementia Clinical Research Program (O.C.O.), Brown Medical School & Rhode Island Hospital, Providence, RI; and Department of Family and Preventive Medicine and Neurosciences (R.R.), University of California San Diego.
Address correspondence and reprint requests to Dr. Daniel C. Marson, Department of Neurology, SC 650K, University of Alabama at Birmingham, Birmingham, AL 35294-0017 dmarson{at}uab.edu
Objective: To investigate longitudinal change in the medical decision-making capacity (MDC) of patients with amnestic mild cognitive impairment (MCI) under different consent standards.
Methods: Eighty-eight healthy older controls and 116 patients with MCI were administered the Capacity to Consent to Treatment Instrument at baseline and at 1 to 3 (mean = 1.7) annual follow-up visits thereafter. Covariate-adjusted random coefficient regressions were used to examine differences in MDC trajectories across MCI and control participants, as well as to investigate the impact of conversion to Alzheimer disease on MCI patients’ MDC trajectories.
Results: At baseline, MCI patients performed significantly below controls only on the three clinically relevant standards of appreciation, reasoning, and understanding. Compared with controls, MCI patients experienced significant declines over time on understanding but not on any other consent standard. Conversion affected both the elevation (a decrease in performance) and slope (acceleration in subsequent rate of decline) of MCI patients’ MDC trajectories on understanding. A trend emerged for conversion to be associated with a performance decrease on reasoning in the MCI group.
Conclusions: Medical decision-making capacity (MDC) decline in mild cognitive impairment (MCI) is a relatively slow but detectable process. Over a 3-year period, patients with amnestic MCI show progressive decline in the ability to understand consent information. This decline accelerates after conversion to Alzheimer disease (AD), reflecting increasing vulnerability to decisional impairment. Clinicians and researchers working with MCI patients should give particular attention to the informed consent process when conversion to AD is suspected or confirmed.
Abbreviations: AD = Alzheimer disease; ADRC = Alzheimer’s Disease Research Center; CCTI = Capacity to Consent to Treatment Instrument; CDR = Clinical Dementia Rating scale; DRS-2 = Dementia Rating Scale, second edition; GDS = Geriatric Depression Scale; MCI = mild cognitive impairment; MDC = medical decision-making capacity; MMSE = Mini-Mental State Examination; UAB = University of Alabama at Birmingham.
Supplemental data at www.neurology.org
Supported by grants 1R01 AG021927 (to D.C.M., Principal Investigator) and 1P50 AG16582 (Alzheimer’s Disease Research Center) (to D.C.M., Principal Investigator) from the National Institute on Aging.
Disclosure: The capacity outcome measure used in the study is owned by the University of Alabama at Birmingham Research Foundation (UABRF). D.C.M. and L.E.H. receive royalty income through UABRF. The other authors report no disclosures.
Received May 12, 2008. Accepted in final form July 22, 2008.
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