State-Level Indicators of Childhood Educational Quality and Incident Dementia in Older Black and White Adults

Importance: Higher educational attainment is associated with reduced dementia risk, but the role of educational quality is understudied, presenting a major evidence gap, especially as it may contribute to racial inequities. Objective: To evaluate the association between state-level educational quality during childhood and dementia risk. Design, Setting, and Participants: This cohort study analyzed longitudinal data collected from January 1, 1997, through December 31, 2019 (23-year follow-up period). The sample comprised members of Kaiser Permanente Northern California (KPNC), a large integrated health care delivery system, who completed an optional survey during 1964-1972. Eligible individuals were US born; non-Hispanic Black or non-Hispanic White; aged 65 years or older as of January 1, 1996; were still alive; and did not have a dementia diagnosis or lapse in KPNC membership greater than 90 days between January 1 and December 31, 1996. Exposures: Historical state-level administrative indicators of school quality (school term length, student-teacher ratio, and attendance rates) linked to participants using birth state and birth year (with a 6-year lag) and divided into tertiles using the pooled sample. Main Outcomes and Measures: Dementia diagnoses from electronic health records between 1997 and 2019 were analyzed between March 1 and August 31, 2022. The associations of educational quality with incident dementia were estimated using Cox proportional hazards regression models. Results: Among 21450 KPNC members who participated in the optional survey, individuals born before availability of educational quality records (n = 87) and missing educational attainment (n = 585) were excluded. The final analytic sample was 20778 individuals (56.5% women, 43.5% men; mean [SD] age, 74.7 [6.5] years; 18.8% Black; 81.2% White; 41.0% with less than high school education). Among Black individuals, 76.2% to 86.1% (vs 20.8%-23.3% of White individuals) attended schools in states in the lowest educational quality tertiles. Highest (vs lowest) educational quality tertiles were associated with lower dementia risk (student-teacher ratio: hazard ratio [HR], 0.88 [95% CI, 0.83-0.94]; attendance rates: HR, 0.80 [95% CI, 0.73-0.88]; term length: HR, 0.79 [95% CI, 0.73-0.86]). Effect estimates did not differ by race and were not attenuated by adjustment for educational attainment. Conclusions and Relevance: In this cohort study, lower state-average educational quality was more common among Black individuals and associated with higher dementia risk. Differential investment in high-quality education due to structural racism may contribute to dementia disparities..