[Nasrudith]

One account I have heard from nurses in Geritology is the apparent importance of "will to live" - they have witnessed many times death following them psychologically giving up.

There could be some chicken vs egg factor (do they lose the will from health being hopeless or does their health decline with their psychological state influencing immune system, and to what extent?). That or spurious human pattern recognition (superstition) but it is possible that there is some literal survivalship bias.