Long-term cognitive effects of an incremental blood pressure intervention in a mortal cohort

We investigate long-term cognitive effects of an intervention, where systolic blood pressure (sBP) is monitored at more optimal levels, in a large representative sample. A limitation with previous research on the potential risk reduction of such interventions is that they do not properly account for the reduction of mortality rates. Hence, one can only speculate whether the effect is a result from changes in cognition or changes in mortality. As such, we extend previous research by providing both an etiological and a prognostic effect estimate. To do this we propose a Bayesian semi-parametric estimation approach for an incremental intervention, using the extended G-formula. We also introduce a novel sparsity-inducing Dirichlet hyperprior for longitudinal data, demonstrate the usefulness of our approach in simulations, and compare the performance relative to other Bayesian decision tree ensemble approaches. In our study, there were no significant prognostic- or etiological effects across all ages, indicating that sBP interventions likely do not have a strong effect on memory neither at the population level nor at the individual level.