Age at dementia diagnosis, subtype associations, and neuroimaging differentiation in Bangladesh: The CARED study

Evidence on age at diagnosis of dementia and differentiation of dementia subtypes in Bangladesh is limited. This study aimed to determine age at diagnosis, examine factors associated with dementia subtypes, and evaluate the discriminatory utility of neuroimaging scales in a Bangladeshi clinical population.

The Community Awareness and Research on Early Dementia (CARED) study was a cross-sectional observational study conducted 2019-2024 at a tertiary care centre in Bangladesh. A total of 658 adults presenting with cognitive impairment, undergoing evaluation for suspected dementia were included. Diagnoses were established using DSM-5 criteria by a multidisciplinary team. Patients were categorized into dementia subtypes. Pseudodementia was retained as separate comparator group. Multivariable regression analyses were performed to identify factors associated with dementia subtypes. Receiver operating characteristic (ROC) curve analyses were used to assess the discriminatory performance of neuroimaging scales.

Among 658 patients, Alzheimer's-related dementia (ARD) accounted for 51.7% of cases. The mean age at diagnosis was significantly higher in ARD compared with non-Alzheimer's-related dementia (nARD) (67.7 ± 10.8 vs 64.3 ± 11.4 years, P < 0.001). In multivariable analysis, nARD was associated with an earlier age at diagnosis by 4.3 years compared with ARD. Vascular dementia was associated with hypertension, OR 4.2 (95% CI 1.1-16.6), P = 0.04, and smoking, OR 13.1 (95% CI 1.6-103.3), P = 0.01. Neuroimaging scales demonstrated variable discriminatory performance. Medial temporal atrophy showed good discrimination for ARD (AUROC 0.752), while Fazekas scores demonstrated good performance for vascular dementia (AUROC 0.838) and mixed dementia (AUROC 0.836). Global cortical atrophy showed moderate discriminatory ability for frontotemporal dementia (AUROC 0.659).

Age at diagnosis varied across dementia subtypes in this Bangladeshi clinical cohort, with non-Alzheimer's diagnosed earlier than Alzheimer's. Structured MRI visual rating scales showed variable subtype-specific discriminatory performance, suggesting that they may provide adjunctive information for dementia subtype differentiation when interpreted alongside multidisciplinary clinical assessment.