Does a terminal decline in systolic blood pressure account for the association between low SBP and higher all-cause mortality in adults >80 years of age?
The paradoxical association between low systolic blood pressure and higher mortality in the very elderly may be driven by reverse causation due to a terminal decline in blood pressure near the end of life.
A terminal decline of SBP in the final 2 years of life suggests that nonrandomized epidemiological associations of low SBP with higher mortality may be accounted for by reverse causation if participants with lower blood pressure values are closer, on average, to the end of life.
Ravindrarajah et al. (2017) studied this question.