We identified studies published between January 2018 and November 2023 using keywords related to decision-making abilities and functional outcomes in aging populations. Search terms used were related to decision-making and older adults (see Ho et al., 2024 for the entire search strategy), including the comprehensive list of decision-making terms (e.g., decision-making, decisional capacity, decision quality, decisional impairment, decision process, choice making) as well as domain specific search terms for themes related to functional outcomes (e.g., functional assessment, functional status, daily living activity, independent living, social competence, full list available in Table 1). Functional outcomes were defined as skills or behaviors related to one's ability to live independently, such as competence in completing both basic and complex activities of daily living. Inclusion/exclusion criteria are listed in Table 2. Studies that only measured shared decision-making or decision aids were excluded as they were not relevant to our goal of understanding measures assessing decision -making in the context of functional outcomes. We included manuscripts with samples of adults ages 45 and over to incorporate studies that focused on the earliest signs of aging. We included empirical studies and meta-analyses. Studies that primarily used single-subject research/case studies or focus groups, as well as publications that were narrative reviews, conference proceedings, book chapters, dissertations, commentaries, pre-prints, or other non-research publications were not included. We included only publications written in English, although measures from all languages were considered.

The scoping review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Review (PRISMA-Scr; Tricco et al., 2018). A comprehensive search and article selection procedure was conducted as part of a larger review on multiple domains of DM (Ho et al., 2024) and a search strategy was developed with the help of a medical research librarian at Northwestern University's Galter Health Sciences Library. We reviewed multiple databases including Embase (Elsevier), MEDLINE (Ovid), PsycINFO (EbscoHost), Cochrane Library (Wiley), Web of Science (Clarivate), and Scopus (Elsevier). The search was conducted to capture publications available from January 1^st, 2018, and November 6^th, 2023.

Following the initial search phase, articles were screened in Covidence, a web-based collaboration platform that streamlines the production of systematic reviews (Veritas Health Innovation, 2024) using the inclusion and exclusion criteria presented in Table 2. This process was carried out in multiple stages. First, titles and abstracts were screened by two independent reviewers. Conflicts were resolved by study scientists or a third reviewer. Included articles were then re-screened using the full text to further assess eligibility. All articles that passed both screening phases advanced to the data extraction phase, where reviewers standardized the process by extracting results using a Qualtrics form (an online survey tool to build, collect, and analyze survey data; Copyright © 2024 Qualtrics, 2024). At this stage, additional articles would still be excluded if they did not meet the inclusion criteria.

Extraction data included information about article sample characteristics (i.e., sample age group, clinical diagnosis if present, control group if present), specific measures (name used in article and standardized name used more commonly), language of the measure, administration method (remote vs. in-person, self-administered vs. technician administered), materials required for administration (computer, paper/pen, interview), reliability/validity metrics (internal consistency, interrater reliability, test-retest reliability, validity metrics) and the most relevant domain areas assessed. Institutional review board approval was not required for this study.

The initial search yielded 32,235 articles (see Figure 1 for review process), including 15,957 duplicate articles, which were removed. Of the 16,278 articles left for review in the title and abstract screening, a total of 14,622 articles were excluded, and full-text screening excluded an additional 869 articles. Of the remaining 787 articles that went through extraction phase, 82 were excluded during extraction resulting in a final set of 705 articles. Of these articles, 301 focused on functional outcomes in an aging population and included 231 unique measures (450 measures used in total). The list of all articles included is presented in Supplementary Table S1, and list of all measures included in the scoping review is presented in Supplementary Table S2.

Among articles classified as assessing functional outcomes, a majority of the measures (76.4%) were administered in person. Of these, 39.2% were administered by an examiner, 45.3% were self-administered under supervision, 8.1% were self-administered without supervision, and for the rest of the in-person measures the administration method was not provided (7.3%). Approximately 14.4% of measures were administered remotely, which included 90.8% of remotely administered measures were self-administered without supervision, 4.6% were administered with an examiner, and 3.1% were self-administered with supervision. The remainder of studies (2.9%) included mixed administration (e.g., in-person and remote) or did not specify administration (6.2%). Approximately half of the studies were conducted in English (47.8%), 6% in multiple languages, 5% in Spanish, and the remainder in other languages (e.g., German, French, Dutch, Mandarin, Japanese, and Greek).

With respect to sample characteristics, all the studies included participants that were 45 years and above, though in some cases (8%) information on the age of participants was not provided but could be inferred (e.g., by the type of disease participants had such as MCI/AD, Parkinson's Disease). Approximately 92% of the studies included participants ages 45 and older only, and 64.1% included participants ages 65 and older only. Approximately 39.9% of the articles included primarily a clinical sample, while 33.2% sampled both clinical and control groups, and 26.9% did not include a clinical sample. The most common conditions of the clinical samples were a diagnosis of MCI/AD, chronic health conditions, Parkinson's disease, psychiatric or substance use disorders, and various brain lesions. Specifically, 14.6% of studies included participants along the cognitive aging spectrum of MCI to various dementias (e.g., Alzheimer's disease, frontotemporal dementia, vascular dementia, unspecified form of dementia), 6.6% included participants with Parkinson's disease, 23.9% included participants with psychiatric or substance use disorders (e.g., schizophrenia, major depressive disorder, obsessive-compulsive disorder, hoarding disorder, gambling disorder, alcohol use disorder), 16.9% with various health conditions (e.g., cancer, sleep apnea, chronic pain, heart failure), and 11.3% with neurologic conditions (e.g., epilepsy, multiple sclerosis, stroke, brain lesions).

Of the 231 unique measures extracted, each was evaluated for its direct relevance to functional outcomes. The most common measures typically fell under three umbrella categories: (1) self or informant-report measures of functional abilities, (2) semi-structured interviews assessing skills such as everyday judgment, and (3) performance-based measures of functional abilities. Relevant studies and subsequent measures are listed under Table 3 and Supplementary Table S3. The most common informant-report measures related to functional outcomes included The Lawton Instrumental Activities of Daily Living (IADL) Scale (n = 25; Lawton and Brody, 1969) and The Barthel Index for Activities of Daily Living (ADL) Scale (n = 12; Mahoney and Barthel, 1965), which are brief informant- or clinician-report questionnaires that assess independence across instrumental activities of daily living (e.g., household chores, transportation, using the telephone, and managing finances) and basic activities of daily living (e.g., toileting, bathing, and mobility) respectively. The Katz Index of Independence in Activities of Daily Living (ADL) Scale (n = 6; Katz et al., 1963) and Functional Activities Questionnaire (FAQ; n = 5; Pfeffer et al., 1982) are similar measures, and focus on basic and instrumental activities of daily living respectively. The Tokyo Metropolitan Institute of Gerontology Index of Competence (TMIG-IC; Koyano et al., 1991), mentioned twice, is a self- or informant-report measure of higher-level functional capacity that covers activities of daily living, intellectual activities (e.g., reading newspapers), as well as social relationships and communication. The Amsterdam IADL Questionnaire (A-IADL; Sikkes et al., 2012) is a novel adaptive and computerized informant-report questionnaire designed to assess impairments in instrumental activities of daily living (IADL) in dementia. The A-IADL also assesses additional domains, including using technology or appliances, occupation skills, and leisure activities. This measure was included once in the scoping review.

Several studies included in the scoping review also utilized semi-structured interviews or measures with open-ended responses. The Test of Practical Judgment (TOP-J; n = 3; Rabin et al., 2007) is a brief interview-based measure that assesses judgment related to safety, medical, social/ethical, and financial issues, by asking questions that reflect real-world scenarios. Assessment of Capacity for Everyday Decision-making (ACED; n = 1; Lai et al., 2008) is a semi-structured interview that measures the capacity to make decisions about solving everyday problems, and assesses four decision-making abilities including understanding, appreciation, reasoning, and expressing a choice. The Everyday Decision-Making Competence task (EDMC; n = 1; Rosi et al., 2019) is another measure that assesses decision-making ability in everyday situations, and consists of decision-making problems about daily, economic, and healthcare scenarios.

Lastly, many studies assessed functional outcomes using performance-based measures. For example, the Timed Instrumental Activities of Daily Living (TIADL; n = 4; Owsley et al., 2001) assesses participants' ability to complete five different tasks where efficient completion would be advantageous including: telephone communication, financial abilities, nutrition, shopping, and medication usage. The Independent Living Scales (n = 3; Loeb, 1996) is a lengthier battery of measures that assesses competence in functional abilities by assessing the areas of memory/orientation, managing money, managing home and transportation, health and safety, and social adjustment; the domains include both performance-based tasks, as well as open-ended questions. The Process Analysis of Daily Activity for Dementia (PADA-D; n = 2; Tabira et al., 2019) is used in individuals with cognitive decline, and includes evaluation of both basic and instrumental activity performances by breaking down each activity into smaller processes and larger actions. The Texas Functional Living Scale (n = 1; Cullum et al., 2001) is a briefer performance-based measure, and includes domains of time, money and calculation, communication, and memory. Lastly, the Performance Assessment of Self-care Skills (PASS; n = 1; Holm and Rogers, 2008) is a comprehensive tool that measures daily life tasks to assist with planning occupation-based interventions across the lifespan; it covers multiple basic and activities of daily living and several mobility tasks.