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BACKGROUND: Long-increasing dementia incidence and prevalence trends may be shifting. Whether such shifts have reached the very old is unknown.

OBJECTIVE: To investigate temporal trends in the incidence of dementia and cognitive impairment and prevalence of dementia, cognitive impairment, Alzheimer's disease, vascular dementia, and unclassified dementia among 85-, 90-, and ≥ 95-year-olds in Sweden during 2000-2017.

METHODS: This study was conducted with Umeå 85 + /Gerontological Regional Database data from 2182 85-, 90-, and ≥ 95-year-olds in Sweden collected in 2000-2017. Using logistic regression, trends in the cumulative 5-year incidences of dementia and cognitive impairment; prevalences of dementia, cognitive impairment, Alzheimer's disease, and vascular dementia; and Mini-Mental State Examination thresholds for dementia diagnosis were estimated.

RESULTS: Dementia and cognitive impairment incidences decreased in younger groups, which generally showed more-positive temporal trends. The prevalences of overall dementia, cognitive impairment, and Alzheimer's disease were stable or increasing; longer disease durations and increasing dementia subtype classification success may mask positive changes in incidences. Vascular dementia increased while unclassified dementia generally decreased. CONCLUSION: The cognitive health of the very old may be changing in the 21st century, possibly indicating a trend break.