The fact that there are still people that don't understand discrimination in this day and age is infuriating. If you think your interview candidate is potentially senile then you should screen for senility and not lump people based on statistical averages for whatever pigeon holes your constructed for them. People need a chance to surpass whatever stereotypes you hold even if they're based on statistically facts.
Not only is it down right illegal, it what perpetuates discrimination and causes so many of our social problems
PS: I'm sorry this is off topic, but this is a very important issue - and simplistic narrow minded thinking like this needs to be pointed out for the common good