Onset of terminal decline in cognitive abilities in individuals without dementia

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Abstract
Objective: To identify time of onset and rate of mortality-related change (terminal decline) in cognitive abilities in later life. Method: The sample consisted of 288 individuals without dementia (born 1901–1902) drawn from the population of Göteborg, Sweden. Participants were followed from age 70 until death, with up to 12 measurement occasions on three cognitive abilities. Change-point analysis was performed using an automated piecewise linear mixed modeling approach to identify the inflection point indicating accelerated within-person change related to mortality. A profile likelihood method was used to identify the change point that best fit the data for each of three cognitive abilities. Results: Onset of terminal decline was identified 6.6 years prior to death for verbal ability, 7.8 years for spatial ability, and 14.8 years for perceptual speed. Conclusions: There is substantial acceleration in cognitive decline many years prior to death among individuals without dementia. Time of onset and rate of terminal decline vary considerably across cognitive abilities.