When does cognitive decline begin? A systematic review of change point studies on accelerated decline in cognitive and neurological outcomes preceding mild cognitive impairment, dementia, and death.

Abstract

Older adults who ultimately develop dementia experience accelerated cognitive decline long before diagnosis. A similar acceleration in cognitive decline occurs in the years before death as well. To evaluate preclinical and terminal cognitive decline, past researchers have incorporated change points in their analyses of longitudinal data, identifying point estimates of how many years prior to diagnosis or death that decline begins to accelerate. The current systematic review aimed to summarize the published literature on preclinical and terminal change points in relation to mild cognitive impairment (MCI), dementia, and death, identifying the order in which cognitive and neurological outcomes decline and factors that modify the onset and rate of decline. A systematic search protocol yielded 35 studies, describing 16 longitudinal cohorts, modeling change points for cognitive and neurological outcomes preceding MCI, dementia, or death. Change points for cognitive abilities ranged from 3-7 years prior to MCI diagnosis, 1-11 years prior to dementia diagnosis, and 3-15 years before death. No sequence of decline was observed preceding MCI or death, but the following sequence was tentatively accepted for Alzheimer's disease: verbal memory, visuospatial ability, executive functions and fluency, and last, verbal IQ. Some of the modifiers of the onset and rate of decline examined by previous researchers included gender, education, genetics, neuropathology, and personality. Change point analyses evidence accelerated decline preceding MCI, dementia, and death, but moderators of the onset and rate of decline remain ambiguous due to between-study modeling differences, and coordinated analyses may improve comparability across future studies. (PsycINFO Database Record

Trajectories of Immediate and Delayed Verbal Memory in the Spanish General Population of Middle-aged and Older Adults

“…However, we expect to find more pronounced differences as more assessments were included, since a longer follow-up would be the proper way to study changes in these cognition trajectories. Nonetheless, according to the systematic review of Karr et al (2018), change points for cognitive abilities ranged from 3 to 7 years before mild cognitive impairment diagnosis. Thus the study of preclinical differences could be useful on the early detection of cognitive change [50].…”

“…Nonetheless, according to the systematic review of Karr et al (2018), change points for cognitive abilities ranged from 3 to 7 years before mild cognitive impairment diagnosis. Thus the study of preclinical differences could be useful on the early detection of cognitive change [50].…”

“…This approach is useful to capture the heterogeneity in individual trajectories and to obtain meaningful latent groups of individuals following similar paths in the outcome of interest, in terms of descriptive analysis [48,49]. Whether the identified trajectories are mainly descriptive, the study of modifiable risk factors associated with those groups is essential to detect groups of individuals to create proper prevention and intervention programs to delay the onset or rate of cognitive decline [50].…”

Profiles of cognitive change in preclinical Alzheimer’s disease using change-point analysis

“…In addition, the use of the bootstrapping analysis not only allows us to capture parameter estimates and standard errors more accurately, but enables the statistical comparison of change-points among different cognitive measures, greatly extending the work of previous studies. [14] In summary, we found that the cognitive measure to show the earliest change in rates of decline in preclinical AD was visuospatial ability rather than episodic memory. Using change-point analyses with bootstrapping can reveal the temporal patterns of accelerated cognitive decline in preclinical AD and may help guide the development of tools for participant screening in clinical trials.…”

Brain Health across the Lifespan: A Systematic Review on the Role of Omega-3 Fatty Acid Supplements

“…Signs of cognitive decline can be evident in adults as young as their twenties [ 12 ]. Rates of cognitive deterioration have been found to accelerate in the 15 years preceding death—this includes 3 to 7 years before mild cognitive impairment diagnosis and to 1–11 years before dementia is diagnosed [ 13 ]. The causes of poor brain health are multi-factorial, quite often having the same modifiable risk factors as cardiovascular disease such as obesity, physical inactivity, smoking, diabetes mellitus and depression [ 14 ].…”