The mixed evidence that high levels of cardiovascular risk factors (CVRF) are associated with lower cognitive test scores of may be due to confounding of age across studies. We pooled and harmonized individual-level data (30,967 persons, age range 42-96y) from five prospective cohorts to examine the trajectories of betas estimating 1-year-age associations of a cognitive outcome (Digit Symbol Substitution Test; DSST) to five CVRF: systolic and e blood pressure, total cholesterol, fasting glucose and body mass index. Linear and quadratic piecewise regression models were fit to the trajectory patterns of these betas. The trajectories showed with each 1-year age increment, higher CVRF were associated with lower DSST, but associations attenuated toward zero as age increased. In addition, the pattern across age of each CVRF-DSST trajectory ranged from linear to non-liner. Without accounting for participant age in cohort comparisons, conclusions about the potential benefit on cognitive function of modifiable CVRF control will continue to be mixed and lead to delays in developing prevention programs.
Keywords: age modification of risk; cardiovascular risk factor; cognitive impairment; life-course.