Clinical characteristics and neuropsychiatric profiles of young-onset dementia: a retrospective cross-sectional study at a tertiary care center in Northern Thailand.

BACKGROUND: Data on young-onset dementia (YOD) in Thailand remain limited. We aimed to describe clinical presentation, general cognitive performance, neuropsychiatric symptoms, neuroimaging features, and selected laboratory findings across YOD subtypes in a tertiary-care cohort in Northern Thailand. METHODS: We conducted a retrospective cross-sectional study of 295 individuals with YOD (symptom onset < 65 years) treated at Chiang Mai University Hospital (2010-2025). Data extracted included demographics, presenting complaints, general cognitive scores (MoCA/TMSE/MSET-10), neuropsychiatric symptoms (NPI-Q, TGDS), functional status, neuroimaging findings, and laboratory results (HIV, syphilis serology, glycemic indices, and lipid profiles). RESULTS: Alzheimer's disease (AD) and vascular dementia (VaD) were the most common subtypes. Memory impairment was the most frequent presenting complaint overall (78.3%) and was more common in AD than VaD (93.4% vs 77.8%), whereas behavioral change was more common in VaD than AD (31.1% vs 13.2%). General cognitive scores did not significantly differ between AD and VaD. Neuropsychiatric symptoms were frequent, with aberrant motor behavior (42.2%) and irritability/lability (35.1%) being the most prevalent domains. Regarding neuroimaging features, a substantial burden of subcortical and basal ganglia lesions co-occurred predominantly within the VaD group. Behavioral variant frontotemporal dementia (bvFTD) accounted for 3.7% of cases; most met the International Behavioral Variant FTD Criteria Consortium (FTDC) criteria for probable bvFTD. All tested participants had non-reactive HIV results, and reactive syphilis screening results were uncommon and were not supported by confirmatory treponemal testing. CONCLUSION: Presenting complaints differed between young-onset AD and VaD despite similar general cognitive performance, underscoring the importance of informant history and multimodal assessment for accurate subtyping. Frequent motor-related neuropsychiatric symptoms highlight the clinical relevance of subcortical/basal ganglia lesion burden in this cohort.