Objectives: To perform a structured literature review of the published empirical research on informed consent with older adults in order to make recommendations to improve the informed consent process and to highlight areas needing further examination.
Design: Relevant literature was identified by searching electronic databases (AGELINE, BIOETHICSLINE, CancerLit, Ethics Index, Health, LegalTrac, MEDLINE, PAIS International, PsycInfo, and Sociofile). Studies were included if they were reports of primary research data about informed consent and, if patients or other subjects were used, older subjects were included in the sample. Data related to the aspect of informed consent under study (recruitment, decision-making capacity, voluntariness, disclosure of information, understanding of information, consent forms, authorization, and policies and procedures) were abstracted and entered into a specially designed database.
Measurements: Characterization of the population, age of subjects, setting, whether informed consent was being studied in the context of research or treatment, study design, the nature of outcome or dependent variables, independent variables (e.g., experimental conditions in a randomized controlled trial or patient/subject characteristics in a nonrandomized comparison), and results according to the aspect of informed consent under study.
Results: A total of 99 articles met all the inclusion criteria and posed 289 unique research questions covering a wide range of aspects of informed consent: recruitment (60); decision making capacity (21); voluntariness (6); disclosure (30); understanding (139); consent forms (7); authorization (11); policies (13); and other (2). In the secondary analyses of numerous studies, diminished understanding of informed consent information was associated with older age and fewer years of education. Older age was also sometimes associated with decreased participation in research. Studies of disclosure of informed consent information suggest strategies to improve understanding and include a variety of novel formats (e.g., simplified, storybook, video) and procedures (e.g., use of health educators, quizzing subjects, multiple disclosure sessions).
Conclusions: A systematic review of the published literature on informed consent reveals evidence for impaired understanding of informed consent information in older subjects and those with less formal education. Effective strategies to improve the understanding of informed consent information should be considered when designing materials, forms, policies, and procedures for obtaining informed consent. Other than empirical research that has investigated disclosure and understanding of informed consent information, little systematic research has examined other aspects of the informed consent process. This deficit should be rectified to ensure that the rights and interests of patients and of human subjects who participate in research are adequately protected.