Alzheimer’s Disease Assessment Scale - Cognitive Subscale (ADAS-Cog): Normative Data for the Portuguese Population

Abstract

Introduction: The Alzheimer’s Disease Assessment Scale – Cognitive Subscale is a brief battery developed to assess cognitive functioning in Alzheimer’s disease that encompasses the core characteristics of cognitive decline (e.g. memory, language, praxis, constructive ability and orientation). The early detection, as well as the monitoring of cognitive decline along disease progression, is extremely important in clinical care and interventional research. The main goals of the present study were to analyze the psychometric properties of the Portuguese version of the Alzheimer’s Disease Assessment Scale – Cognitive Subscale, and to establish normative values for the Portuguese population.
Material and Methods: The Portuguese version of Alzheimer’s Disease Assessment Scale – Cognitive Subscale was administered to 223 cognitively healthy participants according to a standard assessment protocol consisting of the Mini-Mental State Examination, the Montreal Cognitive Assessment and the Adults and Older Adults Functional Assessment Inventory. Normal performance on the assessment protocol was the inclusion criteria for the study.
Results: The Alzheimer’s Disease Assessment Scale – Cognitive Subscale revealed good psychometric properties when used in the Portuguese population. Age was the main predictor of the Alzheimer’s Disease Assessment Scale – Cognitive Subscale total score (R2 = 0.123), whereas the influence of education level was lower (R2 = 0.027). These two variables explained 14.4% of the variance on the Alzheimer’s Disease Assessment Scale – Cognitive Subscale scores and were used to stratify the normative values for the Portuguese population presented here.
Conclusion: On the total sample, the average total score in the Alzheimer’s Disease Assessment Scale – Cognitive Subscale was 6 points. The normative data were determined according to age and educational level as these were the sociodemographic variables that significantly contributed to the prediction of the Alzheimer’s Disease Assessment Scale – Cognitive Subscale total scores, explaining 14.4% of their variance. The normative data are of the utmost importance to ensure proper use of this battery in Portugal.