Methods

Study design and population

This cross-sectional study enrolled 100 community-dwelling adults aged ≥ 60 years without previous stroke, dementia, or other neurological disease. Inclusion criteria were: (1) age ≥ 60 years, having ≥ 1 vascular risk factor, (2) absence of prior neurological disease, dementia, or acute cerebrovascular events (stroke or transient ischemic attack) and (3) absence of depression. Data were collected from July 2024 to August 2025. This study was conducted as an exploratory pilot cross‑sectional study, so the sample size of participants was determined by feasibility of eligible participants recruited during the study period. Written informed consent was obtained, and the study was approved by the Institutional Ethics Committee of Alexandria University Faculty of Medicine (Ethics no. 0108434), in accordance with the Declaration of Helsinki.

Clinical assessment

Demographics (age, sex, body mass index, education: low ≤ 9 years, intermediate > 9–12 years, high > 12 years)5 and vascular risk factors (hypertension; defined as systolic blood pressure ≥ 140 mmHg, diastolic blood pressure ≥ 90 mmHg, or current use of antihypertensive medication, in accordance with the European Society of Hypertension (ESH) guidelines6; diabetes: fasting glucose ≥ 126 mg/dL, 2 h postprandial ≥ 200 mg/dL, or antidiabetics; smoking: non, ex [≥ 12 months], current; history of ischemic heart disease) were recorded.

Ultrasound examination

Carotid duplex ultrasonography was performed by a single examiner using a Philips ClearVue 350 ultrasound system (Philips HealthCare, Best, The Netherlands) with a 4–12 MHz linear array transducer. The examiner was blinded to cognitive status. IMT was measured at the far wall of the distal 10 mm of each common carotid artery (CCA) in the longitudinal plane at the site of maximal thickness. IMT values ≥ 1 mm were classified as increased. Plaques were defined as focal echogenic structures or wall thickening ≥ 1.5 mm7. Stenosis severity was assessed using velocity criteria per the North American Symptomatic Carotid Endarterectomy Trial (NASCET) classification8. The bilateral carotid arterial tree was evaluated at four segments: (CCA), carotid bifurcation, internal carotid artery (ICA) and external carotid artery (ECA). Carotid plaque score quantified cumulative atherosclerotic burden across the four segments bilaterally. Plaque thickness ≥ 1.5 mm, ≥ 2.5 mm, and ≥ 3.5 mm were scored 1, 2, and 3 points, respectively; total plaque score ranged 0–247. The internal carotid artery resistive index (ICA RI) was calculated as: RI = (peak systolic velocity − end-diastolic velocity)/peak systolic velocity9. For each participant, an ICA RI average was computed by mathematically averaging the bilateral (right and left) ICA RI measurements.

Cognitive assessment

Global cognitive function was assessed using validated Arabic versions of the Montreal Cognitive Assessment (MoCA, version 8.3) and the Montreal Cognitive Assessment-Basic (MoCA-Basic). The MoCA-Basic was administered to participants with limited educational attainment or illiteracy, whereas the standard MoCA was administered to the remaining participants. The MoCA-Basic was administered and scored according to the official instructions, including the recommended education adjustments where applicable (+ 1 point for participants with ≤ 4 years of education and + 1 point for illiterate participants, if the total score was < 30). Both instruments generate total scores on a 30-point scale and assess comparable cognitive domains10. Participants were classified as possible MCI, if they had a MoCA score of ≤ 25; applied to both instruments for consistency across the study11. Because both MoCA and MoCA-Basic are screening instruments rather than diagnostic tools, this classification does not represent a clinically confirmed diagnosis of MCI.

Statistical analysis

Continuous variables were summarized as median (interquartile range), categorical variables as counts and percentages. Mann-Whitney U and Kruskal-Wallis tests compared continuous variables between groups. Spearman correlation assessed associations between carotid measures and cognitive scores. Univariate logistic regression identified potential predictors of MCI; variables associated with the outcome of p value < 0.10 in univariate logistic regression were considered for inclusion in multivariable logistic regression models. Age and sex were retained in all multivariable models irrespective of their univariate significance because of their established clinical relevance as potential confounders. Two separate multivariable models were constructed: Model 1 included age, sex, educational level, and carotid plaque score, whereas Model 2 included age, sex, educational level, and ICA RI. Plaque score and ICA RI were analyzed in separate models to evaluate their independent associations with cognitive impairment and to avoid potential overlap between structural and hemodynamic carotid measures. Other risk factors as Hypertension and diabetes mellitus were not entered into the multivariable models because they did not meet the predefined inclusion criterion (p < 0.10) in univariate analysis. Model fit was evaluated with the Hosmer-Lemeshow test and multicollinearity with variance inflation factors. Analyses were conducted using SPSS version 27 (IBM Corp., Armonk, NY, USA).