COGNITIVE RESERVE AS INDEXED BY EDUCATIONAL AND OCCUPATIONAL ATTAINMENT MODERATES THE ASSOCIATION BETWEEN CARDIOVASCULAR DISEASE AND DEMENTIA

Abstract

Cognitive reserve (CR) hypothesis suggests that those with higher levels of reserve can tolerate risk factors of dementia better than those with lower levels of reserve. We tested if higher CR, as indexed by higher educational and occupational attainments, helps to withstand deteriorative effects of cardiovascular disease on cognition. We studied CR, history of cardiovascular disease (CVD) and old age cognition in a sample of 2284 individuals from a population-based Finnish Twin Cohort study. Summary score of middle age CR was based on five questions on educational and occupational status at a mean age of 47 years. Old age cognitive status at a mean age of 74 years was determined with two validated instruments: a self-report interview for cognitive status (TELE) and the Telephone Interview for Cognitive Status (TICS). We used Finnish dementia cutoff scores of <16 and <22.5 for TELE and TICS, respectively. CVD was obtained from hospital discharge registry data. Both CR and CVD were significant predictors of dementia after a mean follow-up of 28 years. There was also a significant CR-CVD interaction indicating that CVD was more strongly associated with dementia in those with low CR compared to those with high CR. In individuals with high CR, 2.6% (TELE) / 1.3% (TICS) of those without CVD and 0% (TELE) / 0% (TICS) of those with CVD were demented. In individuals with low CR, 30.6% (TELE) / 25% (TICS) of those without CVD and 40.5% (TELE) / 37.1% (TICS) of those with CVD were demented. Moreover, the level of CR was more strongly (B = 1.24 [95%CI 1.03; 1.44]) associated with total TELE/TICS score in those with a history of CVD compared to those without a history of CVD (B= 1.00 [95%CI 0.89; 1.11]). Our results support the CR hypothesis whereby those with higher levels of reserve tolerate risk factors of dementia better than those with low levels of reserve. Our results also demonstrate that there may be subgroups who are at elevated risk for dementia due to cardiovascular disease. Detecting high risk subgroups is important for early detection of cognitive impairment and dementia.