Educational inequalities in aging-related declines in fluid cognition and the onset of cognitive pathology.

BACKGROUND: Education has been robustly associated with cognitive reserve and dementia, but not with the rate of cognitive aging, resulting in some confusion about the mechanisms of cognitive aging. This study uses longitudinal data to differentiate between trajectories indicative of healthy versus pathological cognitive aging.

METHODS: Participants included 9,401 Health and Retirement Study respondents aged 55 and older who completed cognitive testing regularly over 17.3 years until most recently in 2012. Individual-specific random change-point modeling was used to identify age of incident pathological decline; acceleration is interpreted as indicating likely onset of pathological decline when it is significant and negative.

RESULTS: These methods detect incident dementia diagnoses with specificity/sensitivity of 89.3%/44.3%, 5.6 years prior to diagnosis. Each year of education was associated with 0.09 (95% CI, 0.087-0.096; P<0.001) standard deviation higher baseline cognition and delayed onset of cognitive pathology (HR, 0.98; 95% CI, 0.96-0.99; P=0.006).

CONCLUSION: Longitudinal random change-point modeling was able to reliably identify incident dementia. Accounting for incident cognitive pathology, we find that education predicts cognitive capability and delayed onset pathological declines.