The Catalan Early Onset Neurodegenerative Dementia Network is a multicenter project launched in 2020 with the aim of understanding the epidemiology and clinical care of people with early‐onset neurodegenerative dementia and their caregivers.

Neurologists and geriatricians visiting patients with cognitive impairment in Catalonia were invited to prospectively collect demographical and clinical data from patients with age at onset (AAO) less than 65 years visited during the year 2021.

We registered information of 1221 subjects from 14 centers. Mean age was 56,2 years (SD 8.7), 64% were woman. Mean age at symptom onset was 53,9 years (SD 9.1). The most frequent cognitive symptoms at onset were memory impairment (72,9%) and dysexecutive difficulties (21,8%). Mean Mini Mental State Examination (MMSE) score was 26,7 (range 7‐30). Initial clinical diagnose was a non‐neurodegenerative disorder in 81,4% of cases and a neurodegenerative disorder in 17,81%. Genetic counseling accounted for 0,8% of visits. The suspected non‐neurodegenerative and neurodegenerative patients were studied with a neuropsychological test (85,5% vs 86,7%, respectively), magnetic resonance imaging (MRI) (39,9% vs 55,6%), computerized tomography (CT) scan (33,2% vs 34,4%), fluorodeoxyglucose positron emission tomography (FDG‐PET) (6,8% vs 39,0%), amyloid‐PET (3,9% vs 34,4%) and lumbar puncture (7,1%, vs 44,8%). 16,6% of participants had a final diagnose of a neurodegenerative cognitive disorder (10,9% Alzheimer’s disease, 2,3% frontotemporal lobular degeneration, 2,1% MCI of suspected neurodegenerative etiology, 0,58% other neurodegenerative dementias); 83,4% were diagnosed with a non‐degenerative disorder (28,4% subjective cognitive decline (SCD), 25,0% mild cognitive impairment of non‐neurodegenerative etiology, 19,8% cognitive impairment after Covid‐19, 10,2% other dementias). Diagnostic delay was higher for neurodegenerative disorders (17 months: median 12 months (interquartile range (IQR) 19) between AAO and first visit +5 months (IQR 8) between first visit and diagnose) than non‐degenerative disorders (12 months: 9 months (IQR 19,6) + 3 months (IQR 7) respectively).

Of 1221 patients under 65 years old visited in cognitive disorders units, only 16,6% had a final diagnose of neurodegenerative cognitive disorder. More than a quarter of subjects were diagnosed as SCD and a fifth as cognitive impairment after Covid‐19. In 2021, diagnosis delay was higher in neurodegenerative disorders (median 17 months).