Person-specific paths of cognitive decline in Alzheimer's disease and their relation to age

Change in global and specific measures of cognitive function was studied in a cohort of 410 persons with Alzheimer's disease. Persons completed up to 5 annual evaluations; follow-up participation among survivors exceeded 90%. Average annual decline was 0.57 standard score units (95% confidence inter val [CI]: -0.51 to -0.62) on a composite measure based on 17 individual tes ts and 3.26 points (95% CI: -3.06 to -3.46) on the Mini-Mental State Examin ation, but substantial heterogeneity was apparent. On both global and speci fic measures, rate of cognitive decline was reduced in older persons compar ed with younger persons. A similar effect was observed for estimated age of disease onset. The effect of age was approximately linear and was not attr ibutable to education, sex, race, other conditions that impair cognition, o r mortality. The results indicate that person-specific paths of cognitive d ecline in Alzheimer's disease vary substantially and suggest that in clinic al settings some of this variability is related to age.