Development and Preliminary Psychometric Testing of a Brief Tool to Measure Medication Adherence in Older Populations

Purpose: Chronic diseases in older age are major sources of burden for healthcare systems. Compliance with medications is the key to treatment success for these patients, especially for frail individuals living in community settings. However, adherence to long-term medications in this population is not optimal, which leads to the need for frequent screening of compliance within large-scale public health surveys. In this context, a brief, simple and valid measure capturing medication adherence is not yet available. This study aims to develop and psychometrically test the Therapeutic Adherence Scale, a brief four-item tool that measures medication adherence in community-dwelling older adults affected by chronic diseases.

Methods: We conducted a three-phase process of instrument development, content validity assessment and psychometric testing.

Results: Of the candidate nine items derived from a review of the literature, only four were deemed essential to capture intentional and nonintentional nonadherence. These items underwent structural validity, convergent and known-groups validity, and internal consistency on a sample of 269 participants (mean age = 7.91 years, SD = 7.26). Confirmatory factor analysis confirmed satisfactory fit indices (RMSEA = 0.000, CFI = 1.00, TLI = 1.00). Scores of the TAS were higher for those perceiving loneliness (ρ = 0.33, p < 0.001), those declaring memory loss in the last year (ρ = 0.29, p < 0.001), and those exhibiting worse mental quality of life (ρ = -0.15, p = 0.03) compared with the other groups. Cronbach's alpha and split-half reliability coefficients were acceptable, with values of 0.68 and 0.77, respectively.

Conclusion: The Therapeutic Adherence Scale is a brief, valid and reliable self-report measure of medication adherence that can be used in practice and research to screen patients living in community settings. This tool is also free to use, which contributes to advancing knowledge on the field of medication adherence of older adults affected by chronic diseases.