There is limited epidemiological evidence about the association between very late-onset schizophrenia-like psychosis (VLOSLP) and dementia. We aimed to examine rate of dementia diagnosis in individuals with VLOSLP compared to those without VLOSLP.Methods: Using Swedish population register data, we established a cohort of 15,409 participants with VLOSLP matched by age and calendar period to 154,090 individuals without VLOSLP. Participants were born between 1920-1949 and followed from their date

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... f first International Classification of Diseases [ICD], Revisions 8-10 (ICD-8/9/10) non-affective psychotic disorder diagnosis after age 60 years old (or the same date for matched participants) until the end of follow-up (30th December 2011), emigration, death, or first recorded ICD-8/9/10 dementia diagnosis. Outcomes: We found a substantially higher rate of dementia in individuals with VLOSLP (hazard ratio (HR):4·22, 95% confidence interval (95%CI):4·05-4·41). Median time-to-dementia-diagnosis was 75% shorter in those with VLOSLP (time ratio:0·25, 95%CI:0·24-0·26). This association was strongest in the first year following VLOSLP diagnosis, and attenuated over time, although dementia rates remained higher in participants with VLOSLP for up to 20 years of follow-up. This association remained after accounting for potential misdiagnosis (2-year washout HR:2·22, 95%CI:2·10-2·36), ascertainment bias (HR:2·89, 95%CI: 2·75-3·04), and differing mortality patterns between groups (subdistribution HR:2·89, 95%CI:2·77-3·03). Interpretation: People with VLOSLP were diagnosed with dementia at a faster rate than those without VLOSLP, which may reflect prodromal dementia for some individuals.