A Bayesian analysis of diagnostic timelines across Alzheimer's disease, frontotemporal dementia, and other neurodegenerative conditions

INTRODUCTION: Timely diagnosis is crucial for managing neurodegenerative conditions. This study investigated whether time from symptom onset to diagnosis differs by clinical syndrome and sex. METHODS: This retrospective, cross-sectional study included 591 participants with Alzheimer's disease (AD), frontotemporal dementia (FTD) subtypes (behavioral variant FTD [bvFTD], semantic dementia [SD], and progressive non-fluent aphasia), logopenic progressive aphasia (LPA), and syndromes associated with movement disorders (corticobasal syndrome, FTD with motor neuron disease [FTD-MND], and progressive supranuclear palsy). Bayesian regression models were used to compute diagnostic timelines. RESULTS: Compared to AD (3.35 years; 95% credible interval [CrI]: 3.03–3.72), SD and bvFTD had additional delays of 9.7 (95% CrI: 1.96–20.64) and 14.82 months (95% CrI: 6.94–25.42), respectively, while FTD-MND was shorter by 11.62 months (95% CrI: −15.7 to −4.68). Men with bvFTD had 23.64 month longer delays than women (95% CrI: 10.35–44.33). DISCUSSION: Diagnostic delays may reflect syndrome-specific clinical features, diagnostic complexity, and sociocultural factors. Findings highlight the need for improved diagnostic pathways and pre-clinical biomarkers to facilitate earlier identification. Highlights: Bayesian analyses revealed that diagnostic delays differ by syndrome and sex. Alzheimer's disease (AD) was diagnosed on average 3.35 years after symptom onset. Diagnoses were delayed in semantic and behavioral variant frontotemporal dementia (bvFTD) compared to AD. Men with bvFTD had longer delays than women. Findings support need for improved diagnostic pathways and pre-clinical biomarkers.