Trajectories of memory decline in preclinical Alzheimer's disease: results from the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Ageing

Memory changes in preclinical Alzheimer's disease (AD) are often characterized by heterogenous trajectories. However, data regarding the nature and determinants of predominant trajectories of memory changes in preclinical AD are lacking. We analyzed data from 333 cognitively healthy older adults who participated in a multicenter prospective cohort study with baseline and 18-, 36-, and 54-month follow-up assessments. Latent growth mixture modeling revealed 3 predominant trajectories of memory change: a below average, subtly declining memory trajectory (30.9%); a below average, rapidly declining memory trajectory (3.6%); and an above average, stable memory trajectory (65.5%). Compared with the stable memory trajectory, high Αβ (relative risk ratio [RRR]= 2.1), and lower Mini-Mental State Examination (RRR= 0.6) and full-scale IQ (RRR= 0.9) scores were independently associated with the subtly declining memory trajectory; and high Αβ (RRR= 8.3), APOE ε4 carriage (RRR= 6.1), and greater subjective memory impairment (RRR= 1.2) were independently associated with the rapidly declining memory trajectory. Compared with the subtly declining memory trajectory group, APOE ε4 carriage (RRR= 8.4), and subjective memory complaints (RRR= 1.2) were associated with a rapidly declining memory trajectory. These results suggest that the preclinical phase of AD may be characterized by 2 predominant trajectories of memory decline that have common (e.g., high Αβ) and unique (e.g., APOE ε4 genotype) determinants.