We estimated the population attributable risk (PAR) based on the hazards ratio (HR) of incident AD associated with the top or bottom quartile of the distribution on a personality trait vs. the rest of the sample (adjusted for the demographic covariates). We used the formula PAR = PRF*((HR–1)/HR),27 where PRF is the prevalence of the risk factor (i.e., 25%). The PAR estimates are calculated for comparisons with established risk factors. PAR estimates, however, are generally based on clinically recognized cut-points (e.g., blood pressure values that define hypertension), whereas we used statistical thresholds for the personality traits. In addition, in calculating the PAR, we are not necessarily assuming a direct causal link between the risk factor and the outcome.
