Onset of terminal decline in cognitive abilities in individuals without dementia

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 Go teborg, 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.