Does educational attainment contribute to risk for delirium? A potential role for cognitive reserve.

BACKGROUND The objective of this study was to determine if level of educational attainment, a marker of cognitive reserve, was associated with the cumulative risk of delirium among hospitalized elders. METHODS We performed a secondary analysis of two hospital-based studies. The first (study 1) was an observational study involving 491 admissions. The second study (study 2) involved consecutive admissions assigned to the usual care condition in a controlled clinical trial, and included 461 persons. All participants were elderly (aged 70+) and free from delirium at admission. The outcome was the occurrence of delirium, as rated by the Confusion Assessment Method during hospitalization. RESULTS In study 1 and 2, 22% and 14% of persons developed delirium (cumulative incidence), respectively. In both studies, risk of delirium was higher among persons with fewer years of education. Controlling for the effect of age, sex, dementia, comorbidity, and severity of illness, each year of completed education was associated with a 0.91 lower odds of delirium (95% confidence interval: 0.87, 0.95): compared to persons with 12 years of education, persons with 7 years of education had 1.6-fold increased odds of delirium (95% confidence interval: 1.4, 2.0). CONCLUSION Hospitalized older persons with low educational attainment are at increased risk for delirium relative to persons with more education. This finding may have implications for the role of cognitive reserve in characterizing individual differences in risk for delirium.