title: Onset and rate of cognitive change before dementia diagnosis: findings from two Swedish population-based longitudinal studies.
abstract: We used data from two population-based longitudinal studies to estimate time of onset and rate of accelerated decline across cognitive domains before dementia diagnosis. The H70 includes an age-homogeneous sample (127 cases and 255 non-cases) initially assessed at age 70 with 12 follow-ups over 30 years. The Kungsholmen Project (KP) includes an age-heterogeneous sample (279 cases and 562 non-cases), with an average age of 82 years at initial assessment, and 4 follow-ups spanning 13 years. We fit mixed linear models to the data and determined placement of change points by a profile likelihood method. Results demonstrated onset of accelerated decline for fluid (speed, memory) versus crystallized (verbal, clock reading) abilities occurring approximately 10 and 5 years before diagnosis, respectively. Although decline before change points was greater for fluid abilities, acceleration was more pronounced for crystallized abilities after the change points. This suggests that onset and rate of acceleration vary systematically along the fluid-crystallized ability continuum. There is early onset in fluid abilities, but these changes are difficult to detect due to substantial age-related decline. Onset occurred later and acceleration was greater in crystallized abilities, suggesting that those markers may provide more valid identification of cases in later stages of the prodromal phase.
authors.affiliation: Department of Psychology, University of Gothenburg, Gothenburg, Sweden. valgeir.thorvaldsson@psy.gu.se
authors.forename: Valgeir
authors.initials: V
authors.lastname: Thorvaldsson
authors.forename: Stuart W S
authors.initials: SW
authors.lastname: Macdonald
authors.forename: Laura
authors.initials: L
authors.lastname: Fratiglioni
authors.forename: Bengt
authors.initials: B
authors.lastname: Winblad
authors.forename: Miia
authors.initials: M
authors.lastname: Kivipelto
authors.forename: Erika Jonsson
authors.initials: EJ
authors.lastname: Laukka
authors.forename: Ingmar
authors.initials: I
authors.lastname: Skoog
authors.forename: Simona
authors.initials: S
authors.lastname: Sacuiu
authors.forename: Xinxin
authors.initials: X
authors.lastname: Guo
authors.forename: Svante
authors.initials: S
authors.lastname: Ostling
authors.forename: Anne
authors.initials: A
authors.lastname: Börjesson-Hanson
authors.forename: Deborah
authors.initials: D
authors.lastname: Gustafson
authors.forename: Boo
authors.initials: B
authors.lastname: Johansson
authors.forename: Lars
authors.initials: L
authors.lastname: Bäckman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D003072:Cognition Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D018672:Community Health Planning; D003704:Dementia / Q000175:diagnosis* / Q000453:epidemiology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009483:Neuropsychological Tests; D013548:Sweden / Q000453:epidemiology