You can block it. The unit won't heat or cool that room anymore though. The return air does effect supply air temp. And heat pump efficiency. With a 60 degree return air temp, the heat pump is more efficient then with a 70 degree return air temp.
We are simply getting contaminated causing otherwise healthy folks to lose the function of their kidneys and for a senior citizen who is already suffering sarcopenia this can be a death sentence because of the complexities associated with Renal Failure.
Even if you are active, you will still experience some muscle loss. Although there is no generally accepted test or specific level of muscle mass for sarcopenia diagnosis, any loss of muscle mass is of consequence, because loss of muscle means loss of strength and mobility.