There's a movement among American home builders for what's known as "Aging in Place". People want to buy a house that will be the last home they ever live in. They want to grow old and ultimately die in the same place. Between the buying and the dying is a long span of time, one hopes, in which the body grows weak and frail, so the design considerations at the pre-planning stages of the home build must take this into effect. Some design features that honor this movement are the utter lack of thresholds. All floors, whether room to room, bathroom to shower, or indoors to outdoors, are completely smooth transitions. This offers less to trip on when the legs are no longer as high stepping as they once were and offer ease of wheelchair access. Similarly, while doorknobs were once the default, more and more homes are being build with lever-handled "knobs". These levers offer greater leverage for lower exertion when the arms are not as powerful, or the hands no longer as dextrous, and are easier to use when young and spry at the same time. Similarly again, rather than little clitorii of a light switch poking out of the wall, large, easily hit rocker-type light switches are easier to frobnicate whether young or old.
I have a hobby of designing my dream house, which seems to change radicly every couple of years, but I always try to keep the "Aging in Place" movement foremost in my mind. To this end, I've always wanted for every interior door to be at least 7' tall and 3' wide, and a standard 1˝" thick, while I want my exterior doors to be 7' X 4' X 2", perhaps even stretching up to 8' tall if there is no transom light.