Psychometric evaluation of the Alzheimer's Disease Knowledge Scale in Ecuadorian university students

Abstract

Background

Alzheimer's disease (AD) is the leading cause of dementia worldwide, with rising prevalence, high costs, and significant impact in Ecuador. Awareness and validated tools like the Alzheimer's Disease Knowledge Scale (ADKS) are crucial to improve training and early care.

Objective

To evaluate the reliability and factorial structure of the ADKS in Ecuadorian university students enrolled in health science programs.

Methods

A total of 1089 students completed the ADKS. Internal consistency was assessed using Cronbach's alpha and McDonald's omega coefficients. Confirmatory factor analysis (CFA) was conducted using a Diagonally Weighted Least Squares (DWLS) estimator to evaluate the scale's structure.

Results

The ADKS demonstrated acceptable internal consistency (α = 0.767, ω = 0.770). CFA supported the original one-factor model with strong fit indices (RMSEA = 0.047, SRMR = 0.012, CFI = 0.987, TLI = 0.973, RNI = 0.987, NFI = 0.986, RFI = 0.972, IFI = 0.987). These results confirm the scale's internal validity in this population.

Conclusions

The ADKS is a reliable and valid instrument for assessing knowledge of Alzheimer's disease among Ecuadorian university students. Its use is recommended for both clinical training and public health education strategies focused on dementia awareness.

Keywords

Alzheimer’s disease Alzheimer's Disease Knowledge Scale (ADKS)dementia knowledge psychometrics surveys and questionnaires university students

Introduction

Approximately 55 million people worldwide have dementia, of which more than 60% live in low- and middle-income countries.¹ Alzheimer's disease (AD) is the most common form of dementia in older adults, significantly affecting memory, language, and daily functioning,² and accounts for between 60% and 70% of cases.³ In Ecuador, AD affects 5% of people over 65 years of age, with an exponential increase in the following age groups, reaching 30% in those over 80 years of age and 50% in those over 90 years of age.^4,5

Each year, nearly 10 million new cases are diagnosed worldwide.⁶ In 2015, the estimated global cost of dementia was equivalent to ∼1.1% of global gross domestic product (GDP),⁷ with an increase of approximately US$500 billion in dementia-related expenditures between 2015 and 2019, according to data from the United Nations Population Fund.⁴ Dementia disproportionately affects women, both directly and indirectly.⁸

Given its global impact, it is essential that future healthcare professionals have a solid understanding of this disease in order to provide quality care. Life expectancy is projected to increase by 5 years by 2050, which would lead to a substantial change in the proportion of older adults and, consequently, an increase in disability-adjusted years (DALYs) for AD and other dementias.⁹ This result is a crucial source of information to promote awareness, early diagnosis, and treatment of associated symptoms.¹⁰

The application of AD knowledge tests promotes interest in diagnostic, therapeutic, and support options among health science students, offering a supportive environment that facilitates understanding of a complex disease with significant social and family impact, enabling the search for the best way to provide help.

Measures for detecting AD knowledge can facilitate the creation of strategies for timely care. Therefore, various assessment instruments have been created, such as the Global Deterioration Scale (GDS),¹¹ and the Functional Assessment Staging (FAST),¹² which focus on the stages of the disease and functional decline rather than on specific knowledge about it. The Alzheimer's Disease Knowledge Scale (ADKS), developed by Carpenter et al.,¹³ is the most widely used tool for measuring AD knowledge. However, its use in health sciences students requires specific psychometric validation to ensure its relevance and reliability in this context. The ADKS was selected for this study because it offers a unique approach, measuring knowledge across seven dimensions based on the areas of greatest expression of dementia. This distinction allows for a more comprehensive understanding of dementia knowledge, especially in populations where healthcare providers will be involved in the short term.

Low awareness of AD is often accompanied by late diagnoses, unnecessary procedures, incorrect therapeutic strategies, and inadequate family counseling, generating distress for patients and families. Measures to increase awareness of AD can help identify the aspects that future health professionals find difficult in their training.

This questionnaire not only presented good psychometric properties in the original study by Carpenter et al.,¹³ but multiple studies have also demonstrated the suitability of the scale in different populations, including pharmacists,¹⁴ the general population,¹⁵ and health professionals.¹⁶ For example, a study conducted in Greece¹⁷ focused on evaluating the psychometric properties of the ADKS in a sample of general practitioners in care practice. The study involved 112 physicians. The results of the confirmatory factor analysis (CFA) supported a 1-factor correlated model, which distinguishes differences in knowledge according to the domains assessed. Internal consistency was satisfactory (α = 0.65). Furthermore, high instrument repeatability was found during retesting with 27 general practitioners (intraclass correlation coefficient = 1.0), and inter-item correlation revealed a high cross-correlation between questionnaire items (α > 0.6), confirming the validity of the Greek version of the ADKS for measuring general practitioners’ knowledge of dementia diagnosis and management.

In 523 nursing students from a university in Cuenca, Ecuador,¹⁸ good internal consistency was demonstrated (Cronbach's α = 0.78), adequate test-retest reliability (p < 0.05), and convergent and discriminative evidence of validation when related to other variables.

Good psychometric properties have also been found in the Korean adult population.¹⁵ This study included 575 subjects from the general population. The KR 20 was 0.71 and the ICC was 0.90, indicating that the ADKS-K exhibits internal consistency and stability reliability. Thirty items from the ADKS-K exhibited significant content validity ratio (CVR) values, with a mean of 0.82 and a range of 0.60 to 1.00. The mean item difficulty and the calculated discrimination indices were −0.60 and 0.77, respectively, indicating that the ADKS exhibits an acceptable level of difficulty and discrimination efficiency.

In Latin America, the validation and application of the ADKS remains limited, although its adaptation and use have the potential to contribute significantly to the exploration of AD knowledge in the region. While the study by Ramírez-Coronel,¹⁸ included Latin American participants, they only represented a small sample. However, the psychometric properties of the ADKS can be found published in Portuguese,¹⁹ and Spanish, including the Spanish population.¹⁴ These studies underscore the instrument's value for assessing AD knowledge in various clinical and teaching contexts. However, most of these studies have focused primarily on evaluating its factorial structure. This limited scope may restrict our understanding of the instrument's construct validity, as it is crucial to confirm its internal structure in addition to establishing its association with other relevant measures of dementia knowledge. Few studies have investigated the psychometric properties of the ADKS in Ecuador.

Table 1.

Descriptive of the sociodemographic variables (n = 1089).

Characteristic	N = 1089
Sex
Man	284 (26%)
Woman	805 (74%)
Marital status
Married	49 (4.5%)
Separated/Divorced	14 (1.3%)
Single	984 (90%)
Free Union	42 (3.9%)
Residence
Rural	356 (33%)
Urban	733 (67%)
Ethnicity
Afro-Ecuadorian	6 (0.6%)
White	12 (1.1%)
Indigenous	40 (3.7%)
Mestizo	1031 (95%)
University Degree (Student of)
Nursing	773 (71%)
Medicine	176 (16%)
Psychology	140 (13%)
Has contact with people with dementia?
No	979 (90%)
Yes	110 (10%)
Family history of cognitive impairment?
No	944 (87%)
Yes	145 (13%)
Lives with a family member with dementia?
No	1046 (96%)
Yes	43 (3.9%)

n (%), the mean age was 30.93 years (Age Mn 19 years and Age Mx 25 years).

Methods

This study employed a cross-sectional psychometric validation design to evaluate the reliability and factor structure of the ADKS. Data were collected through an online survey from a sample of Ecuadorian university students. CFA was conducted to assess the scale's structural validity, and internal consistency was evaluated using Cronbach's alpha and McDonald's omega.

This study adheres to the Journal Article Reporting Standards (JARS) for quantitative research, as outlined by the American Psychological Association.²⁰ The study design, data collection, analysis, and reporting procedures followed these guidelines to ensure transparency, replicability, and methodological rigor.

Participants

The sample consisted of a total of 1089 Ecuadorian health sciences undergraduate students from a private university in Cuenca, Ecuador (n = 773 nursing, n = 176 medicine, n = 140 psychology) ranging in age from 18 to 39 years (M = 22.3, SD = 3.05). A total of 284 men and 805 women participated. No other inclusion criteria were used. All participants reported having no previous diagnosis of mental disorder, as assessed by a screening question. No other inclusion or exclusion criteria were applied.

No formal sample size calculation was performed prior to data collection. However, based on recommendations for psychometric validation studies, a minimum of 200 participants is generally considered appropriate for CFA.²¹ Because the ADKS comprises a unifactorial structure, the final sample size of 1089 exceeds these recommendations, providing adequate power for statistical analyses. Nevertheless, the absence of a formal priori power analysis is acknowledged as a limitation of the study.

Alzheimer's Disease Knowledge Scale

This questionnaire was designed and validated by Carpenter,³ to assess knowledge about AD using a 1-factor structure composed of 30 items. The scale includes 7 thematic domains: 1) risk factors (I-2, I-13, I-18, I-25, I-26, I-27), 2) symptoms (I-19, I-22, I-23, I-30), 3) assessment and diagnosis (I-4, I-10, I-20, I-21), 4) course of disease (I-3, I-8, I-14, I-17), 5) impact on life (I-1, I-11, I-28), 6) treatment and management (I-9, I-12, I-24, I-29), and 7) care (I-5, I-6, I-7, I-15, I-16). This thematic variety ensures the content validity of the instrument, but the seven domains should not be considered subdimensions or factors in a psychometric sense. Responses were evaluated using dichotomous yes/no answers. For the present study, the ADKS, adapted and validated for the Ecuadorian context by Ramírez-Coronel was used.¹⁸

An ad hoc survey was administered with sociodemographic variables (sex, marital status, place of residence, ethnic self-identification, contact with a person with dementia (yes/no), family history of cognitive impairment, and whether currently living with a person with dementia).

Procedure

Participants were invited to participate in the study through institutional email campaigns targeting potential participants at the University of Cuenca (3121 students were recruited) between March 11 and April 1, 2024. A total of 1089 students responded to the invitation (nursing n = 773; 71%; medicine n = 176; 16%; psychology n = 140; 13%). The emails included a brief description of the study's objectives, information on the voluntary nature of participation, and a link to the online survey platform hosting the questionnaire. Upon accessing the link, participants were presented with an informed consent form describing the objectives, procedures, confidentiality measures, and the right to withdraw from the study at any time without consequences. Only participants who gave their explicit consent by clicking “Accept” had access to the questionnaire. All responses were securely stored in an encrypted database accessible only to the principal investigator. The data was properly anonymized.

The questionnaire was administered online, and participants were able to complete it at their leisure. To ensure privacy, no identifiable information (e.g., names, email addresses, or IP addresses) was collected. All responses were securely stored in an encrypted online database, accessible only to the principal researcher. This database complied with data protection regulations to safeguard the confidentiality and anonymity of participants.

Analysis

The psychometric properties of the ADKS were determined by assessing internal consistency to determine reliability and the overall score using Cronbach's α and McDonald's omega coefficients. Reliability was interpreted according to standard guidelines, with values above 0.70 considered acceptable, 0.80 considered good, and 0.90 considered excellent. The factor structure of the ADKS was then assessed using CFA to examine the original one-factor correlation model. The analysis employed the diagonally weighted least squares (DWLS) estimator, which is appropriate for ordinal data. Model fit was assessed using multiple fit indices, including the chi-square statistic²² (χ²), the root mean square error of approximation²³ (RMSEA), the standardized root mean square residual²⁴ (SRMR), and incremental fit indices such as the Tucker-Lewis index.²⁵ (TLI) and the comparative fit index.²⁶ (CFI). Additionally, index like Relative Noncentrality Index (RNI), Normed Fit Index (NFI), Relative Fit Index (RFI), and Incremental Fit Index (IFI). The acceptable cutoff points were values greater than 0.90 for the aforementioned indices.²⁶

Following conventional guidelines, acceptable model fit was determined based on RMSEA values less than 0.08 for acceptable fit and less than 0.05 for good fit,²⁷ SRMR values less than 0.08, and TLI and CFI values greater than 0.90 for acceptable fit and greater than 0.95 for good fit.^24,26 Factor loadings and correlation between domains were also examined to assess model adequacy. Items were retained if their factor loadings were greater than 0.50, indicating strong item-level contributions to their respective factors.²⁸

Results

Sociodemographic variables

The results show a dataset of 1089 participants. The majority were women (n = 805; 74%). 90% of the subjects were single. 67% lived in urban areas. The majority of participants self-identified as mixed-race (95%, n = 1031). Only 10% of participants had had contact with people with dementia, and 13% had a family history of cognitive impairment. Finally, 3.9% lived with a family member with dementia (n = 43) (Table 1).

Reliability

The scale obtained Cronbach's alpha coefficients between 0.758 and 0.766 and McDonald's ω between 0.760 and 0.769, indicating acceptable internal consistency for exploratory purposes. Some individual domains, such as care and treatment, showed lower alpha values, which could indicate the need for revision of specific items. The total scale score also had a mean of 0.670 and SD = 0.162 (Cronbach's α = 0.767 and McDonald's ω = 0.770), demonstrating acceptable overall reliability for the scale.

The results of the internal consistency analyses (Table 2) demonstrated acceptable reliability for independent items. Most incorrect responses were located on items A3, A8, A18, and A25, with means between 0.388 and 0.497. However, the correlation between the independent items showed a good result, obtaining scores between 0.183 (item A8) and 0.341 (item A14).

Table 2.

Reliability and validity of ADKS in Ecuadorian university students.

	Mean	SD	Item-total correlation	Cronbach's α	McDonald's ω	Factor loading
A1	0.773	0.419	0.264	0.761	0.764	0.313
A2	0.770	0.421	0.228	0.763	0.766	0.268
A3	0.450	0.498	0.221	0.764	0.766	0.264
A4	0.777	0.417	0.255	0.762	0.764	0.301
A5	0.728	0.445	0.252	0.762	0.764	0.301
A6	0.882	0.322	0.198	0.764	0.767	0.227
A7	0.754	0.431	0.290	0.760	0.762	0.339
A8	0.421	0.494	0.183	0.766	0.769	0.191
A9	0.790	0.408	0.278	0.761	0.763	0.322
A10	0.736	0.441	0.312	0.759	0.762	0.365
A11	0.520	0.500	0.335	0.758	0.761	0.388
A12	0.702	0.458	0.333	0.758	0.761	0.388
A13	0.548	0.498	0.200	0.765	0.768	0.215
A14	0.802	0.399	0.341	0.758	0.760	0.394
A15	0.612	0.488	0.292	0.760	0.763	0.337
A16	0.770	0.421	0.301	0.760	0.762	0.345
A17	0.770	0.421	0.236	0.763	0.765	0.260
A18	0.388	0.487	0.270	0.761	0.765	0.281
A19	0.592	0.492	0.327	0.758	0.761	0.367
A20	0.669	0.471	0.331	0.758	0.761	0.364
A21	0.786	0.410	0.338	0.758	0.760	0.391
A22	0.700	0.459	0.320	0.759	0.761	0.374
A23	0.720	0.449	0.290	0.760	0.763	0.344
A24	0.646	0.478	0.334	0.758	0.761	0.380
A25	0.497	0.500	0.226	0.764	0.767	0.234
A26	0.529	0.499	0.273	0.761	0.765	0.284
A27	0.723	0.448	0.294	0.760	0.763	0.336
A28	0.754	0.431	0.258	0.762	0.764	0.296
A29	0.778	0.416	0.232	0.763	0.765	0.276
A30	0.528	0.499	0.253	0.762	0.765	0.270
Total scale:	0.670	0.162		0.767	0.770

Summary measures of the items (n = 30) of the ADKS Ecuador. χ² (404) = 1387, CFI = 0.987, SRMS = 0.052, RMSEA = 0.047. RNI = 0.987, NFI = 0.986, RFI = 0.972, IFI = 0.987.

Factor analysis

The factors analyzed were interpreted as: (1) general clinical knowledge, (2) symptoms and progression, and (3) management and care. Some items had weak factor loadings (< 0.30), indicating the need for future revisions.

Analysis of the original ADKS structure as a one-factor model (Figure 1) using CFA with the DWLS estimator showed evidence of a good-fitting model. The RMSEA = 0.047 suggested a reasonably good fit, SRMR = 0.012 indicated minimal discrepancies between the model and the observed data, CFI = 0.987, and TLI and NNFI showed values of 0.973, indicating a good fit. The RNI (0.987) and NFI (0.986) values suggest a strong fit for the model, as did the RFI and IFI, which also demonstrated excellent fit, with values of 0.972 and 0.987, respectively.

Figure 1.

Differences in total score according to health career type. An ANOVA test was applied. F (2) = 0.909; p = 0.404.

Slight variability was found in the average scale scores according to the specialty studied, with a very similar mean in medicine (M = 20, SD = 3.75) and nursing (M = 20.2, SD = 4.94), in contrast to psychology students, who had a lower mean (M = 19.6, SD = 5.69), although not significantly so (ANOVA = 0.909, p = 0.404).

Discussion

The present study aimed to evaluate the psychometric properties of the ADKS in a sample of Ecuadorian university students studying medicine, nursing, and psychology, providing evidence for its use in Spanish-speaking contexts, where the level of knowledge about dementias in general and AD in particular represents a significant social and public health problem.

First, internal consistency analyses showed that the individual ADKS items, as well as the overall score, exhibit acceptable reliability. This finding is consistent with previous studies conducted with students in other cultural contexts, such as South Korea,¹⁵ where similar levels of internal consistency were reported.

Construct validity was assessed by analyzing its factor structure using a 1-factor model (disease knowledge). Unlike previous studies that have used estimators such as maximum likelihood (ML),^{3,14,15,29–32} we consider the ordinal nature of the items important. In this study, the DWLS estimator was considered given that the responses to the ADKS items were dichotomous. This allowed for a more robust estimation of the parameters and standard errors, as well as greater precision in the fit indices. Several items exhibited factor loadings exceeding this threshold of 0.30, such as RMSEA, SRMR, TFI, and TLI, which together suggested that the model is adequate. The high factor loadings of the items reinforce the stability of the model in this population.

Although one of the items obtained a factor loading of 0.30, this value is considered the minimum acceptable in psychometric terms.³³ Furthermore, the item addresses a relevant aspect of the construct not covered by the other items, which contributes to the content validity of the scale. The exclusion of the item did not significantly increase the reliability indices, so it was decided to keep it in the model.

The findings support the use of the ADKS as a viable tool for assessing AD knowledge in health sciences students. The ADKS, developed by Carpenter et al.,¹³ have established itself as a valuable tool for assessing AD knowledge in diverse populations. The results obtained in the reviewed studies provide converging evidence on its applicability, although they also reveal certain challenges related to its psychometric structure, especially when implemented in diverse cultural and linguistic contexts.

In the seminal study by Carpenter et al.,¹³ the ADKS demonstrated adequate reliability in terms of both internal consistency and temporal stability (test-retest), in addition to having sufficiently robust content, predictive, and concurrent validity. This initial evaluation, with a diverse sample, was essential to position the scale as a useful tool for assessing knowledge in the general population, caregivers, patients, and professionals. The 30-item design with dichotomous responses and the coverage of seven thematic domains allows for a broad exploration of AD knowledge, facilitating its use in educational and clinical settings.

However, subsequent studies that have validated translated versions of the ADKS, such as those conducted by Leszko and Carpenter,²⁹ in Poland and by Kim and Jung,¹⁵ in Korea, suggest that, although the scale retains acceptable psychometric properties in other languages and cultures, there are differences in terms of factor structure and item functioning. For example, the Korean version (ADKS-K) reported a KR-20 coefficient of 0.71 and an ICC of 0.90, indicating good internal consistency and stability. However, the analysis of item difficulty and discrimination index revealed variability, which may be attributed to cultural, educational, or language interpretation factors.

More critically, the study by García-Ribas et al.,¹⁴ used advanced methods based on Item Response Theory (IRT), particularly Mokken analysis, to explore the dimensionality of the ADKS. The findings were particularly relevant, as they revealed that most items did not fit a unidimensional structure, with a scalability coefficient H = 0.033, which is substantially lower than the acceptable threshold (H ≥ 0.3). This suggests that although the ADKS items offer a broad overview of AD knowledge, they do not necessarily comprise a single latent dimension. Despite this, the authors conclude that the scale remains useful as an informative tool, although its interpretation as a unidimensional construct should be done with caution.

The finding of semi-structured domains, such as those related to depression, prevention, and risk factors, reinforces the notion that AD knowledge is multifaceted and may require tools with more complex or domain-specific structures. This perspective also aligns with the objectives of the Polish study by Leszko and Carpenter,²⁹ who recognize the usefulness of the ADKS for evaluating educational interventions for caregivers and professionals, but caution about the need for culturally adapted and validated measures.

Overall, the available evidence indicates that the ADKS has good basic psychometric properties such as reliability, content validity, and general applicability, but it has limitations in terms of its internal structure and ability to consistently discriminate between different levels of knowledge. This becomes especially relevant in educational contexts, such as that of health science students, where accurate knowledge measurement is expected to support curricular programs and pedagogical strategies.

Finally, the lack of a monotonic homogeneity model, as demonstrated by García-Ribas et al.,¹⁴ and the cross-cultural variability in item performance suggest that the ADKS, although valuable, should be considered more as a general knowledge screening or diagnostic tool, rather than as a highly accurate measurement instrument for individual clinical or educational decisions.

Conclusion

The ADKS presents adequate psychometric properties in health sciences students, with acceptable reliability and preliminary evidence of construct validity. Its use is recommended as a diagnostic and educational tool, especially in programs seeking to improve dementia literacy. For future studies, it is recommended to use larger sample sizes, include non-expert populations, and conduct invariance testing. Researchers could also consider confirmatory analyses and curricular adaptation of the instrument.

Limitations and future directions

Despite its contributions, this study has some limitations that should be considered. First, the sample consisted exclusively of students from a specific city in Ecuador, which limits the generalizability of the findings to other populations and contexts. Future studies should include more diverse samples spanning different regions and age groups to evaluate the cross-cultural validity of the ADKS in other subgroups of the Ecuadorian population. Furthermore, the convergent and discriminant validity measures of the ADKS should be evaluated against other scales that assess constructs related to AD knowledge.

Footnotes

Acknowledgements

The authors thank the participants and collaborating institutions for their valuable contributions to this study. Besides, we would like to express our sincere gratitude to Professor Carpenter for his kind support and generosity in providing access to the Alzheimer's Disease Knowledge Scale (ADKS). His collaboration was instrumental to the development of this study and greatly contributed to advancing our research on Alzheimer's disease knowledge in our target population.

ORCID iDs

José Alejandro Valdevila Figueira

María Alejandra Espinosa de los Monteros

Ethical considerations

This study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki and adhered to national and institutional research ethics guidelines. Participation was voluntary, and informed consent was obtained electronically from all students prior to data collection. Confidentiality and anonymity of participants were strictly maintained throughout the study.

Consent to participate

All participants provided informed consent before taking part in the study. They were informed about the objectives, procedures, confidentiality measures, and their right to withdraw from the study at any time without penalty. Only students who electronically accepted the informed consent form were included in the study.

Consent for publication

Not applicable

Author contribution(s)

José Valdevila Figueira: Data curation; Investigation; Project administration; Writing – original draft; Writing – review & editing.

Andres Ramirez: Data curation; Formal analysis; Investigation; Writing – original draft; Writing – review & editing.

Alejandra Espinoza de los Monteros: Data curation; Writing – original draft; Writing – review & editing.

Rocio Valdevila: Data curation; Investigation; Validation; Writing – original draft.

Indira Carvajal: Data curation; Investigation; Writing – original draft; Writing – review & editing.

Lilia Rometo Sacoto: Data curation; Formal analysis; Writing – original draft.

Maria Pico: Data curation; Investigation; Writing – original draft; Writing – review & editing.

Funding

The authors received financial support for the research, authorship, and/or publication of this article: Funding for the publication of this article was provided by Universidad Politécnica Salesiana, Cuenca, Ecuador.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability statement

Anonymized data that support the findings of this study may be made available from the corresponding author upon reasonable request.

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