Disability Index (DI)

Abstract

The Disability Index (DI; Zhang et al., 2023) is an inventory/questionnaire designed to measure disability status in older adults, specifically assessing activities of daily living, instrumental activities of daily living, physical performance, and cognitive function to determine care needs. Developed based on the experiences of the Frailty Index (FI; Searle et al., 2008) and the Successful Aging Index (SAI; Cosco, Stephan, & Brayne, 2015), the DI consists of 21 items. The cognitive function domain utilizes the total score of the Chinese version of the Mini-Mental State Examination (MMSE; Zhang et al., 2020). Data for its development were collected from older adults aged 65-105 years old across 22 provinces in China, divided into four age subgroups. The study reported on the reliability and various forms of validity (convergent, divergent, known-groups, concurrent), though test-retest reliability was not assessed and is recommended for future evaluation.

Keywords

Activities of Daily Living, Cognitive Function, Disability, Divergent Validity, Instrumental Activities of Daily Living, Known-Group Validity, Older Adults, Physical Performance, Cognitive Ability, Disabilities, Disability Evaluation, Functional Status, Geriatric Assessment, Physical Health, Physical Mobility, Physical Health Assessment, Older Adulthood

Authors

Zhang, Xuxi; Lin, Lizi; Sun, Xinying; Lei, Xiaoyan; Liu, Gordon G.; Raat, Hein; Zeng, Yi

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Purpose

The Disability Index (DI) was developed with the purpose of assessing disability, encompassing activities of daily living, instrumental activities of daily living, physical performance, and cognitive function, in order to identify care needs among older adults.

Validity

Convergent/Divergent Validity: The convergent and divergent validity of the four subdomains of the DI were supported by correlations with corresponding alternative measurements, observed in both the total sample and each age subgroup.

Known-Group Validity: The known-group validity of the full DI and its four subdomains was supported by their clear discriminative ability across the total sample and within each age subgroup.

Concurrent Validity: The concurrent validity of the full DI was found to be excellent, with Area Under the Curve (AUCs) values of ≥0.8 in the total sample. For individual age subgroups, it was generally acceptable, with most AUCs ≥0.7. However, when using “Heavy informal care burden” as the criterion, AUCs in the 65–79 years old and 100–105 years old groups ranged from 0.64 to 0.69, which were slightly below 0.7.

Reliability

Internal Consistency: The internal consistency was assessed using Cronbach’s alpha. For the total sample, the Cronbach’s alpha values were:

• Full DI: 0.94

• Activities of Daily Living (ADL) domain: 0.87

• Instrumental Activities of Daily Living (IADL) domain: 0.95

• Physical Performance domain: 0.72

Within each age subgroup, the Cronbach’s alpha for the full DI, ADL, and IADL domains was consistently ≥0.70. For the physical performance domain, Cronbach’s alpha varied between 0.66 and 0.68 across all age subgroups.

Factor Analysis

No factor analysis was indicated in the provided text.

Instrument

Test Type: Original
Format: Items related to ADL, IADL, and physical performance domains are typically measured on a 3-point scale, ranging from “able to perform the activity without difficulty” to “unable to perform the activity independently.” An exception is items 4–6 in the physical performance domain, which range from “both hands can perform the activity” to “neither hand can perform the activity.” Each item from the ADL, IADL, and physical performance domains is converted into its own index, averaged, and then incorporated into the full DI as a single item. For the cognitive function domain, measured by the MMSE total score, four categories are assigned fractional values: severe impairment (score range 0-17) is assigned 100, moderate impairment (18-21) is 67, mild impairment (22-25) is 33, and no cognitive impairment (26-30) is 0. A total score for the full DI (21 items) ranges from 0 to 100, calculated by averaging the item scores, with higher values indicating a greater level of disability.
Language Available: English
Population Group: Human; Male; Female
Age Group: Adulthood (18 yrs & older); Aged (65 yrs & older); Very Old (85 yrs & older)
Population Details: The study population consisted of older adults, aged 65-105 years old, from 22 provinces in China.
Test Methodology: The methodology included assessments of Test Validity (Concurrent Validity, Convergent Validity, Discriminant Validity) and Test Reliability (Internal Consistency).

Authors

Author ORCID Identifier:

• Zeng, Yi: http://orcid.org/0000-0001-8354-2945

Affiliation Email Addresses:

• Zeng, Yi: [email protected]

Affiliations:

• Zhang, Xuxi: Center for Healthy Aging and Development Studies, National School of Development Peking University

• Lin, Lizi: Department of Occupational and Environmental Health School of Public Health, Sun Yat-sen University

• Sun, Xinying: Public Health School, Health Science Center Peking University

• Lei, Xiaoyan: Center for Healthy Aging and Development Studies, National School of Development Peking University

• Liu, Gordon G.: National School of Development, Peking University

• Raat, Hein: Department of Public Health, Erasmus University Medical Center

• Zeng, Yi: Center for Healthy Aging and Development Studies, National School of Development Peking University

Correspondence Address:

• Zeng, Yi: Duke University Medical School, Center for the Study of Aging and Human Development, 40 Duke Medicine Cir, Durham, North Carolina, United States, 27710, [email protected]

Permissions & Fee and Test Year

Permissions: Contact Corresponding Author
Commercial: No
Fee: No
Test Year: 2023

References

Zhang, X., Lin, L., Sun, X., Lei, X., Liu, G. G., Raat, H., & Zeng, Y. (2023). Development and validation of the Disability Index among older adults. The Journals of Gerontology: Series A: Biological Sciences and Medical Sciences, 78(1), 111–119. https://doi.org/10.1093/gerona/glac059

Items of the Disability Index (DI)

The Disability Index is a 21-item measure composed of items categorized into four domains:

• Activities of Daily Living (ADL)

• Instrumental Activities of Daily Living (IADL)

• Physical Performance

• Cognitive Function

No data is Available regarding the specific content of the 21 items.