I believe you've just answered your own question - To my knowledge, a mortality table does not and should not be factored in during the underwriting process of a long term loan such as a mortgage, also known as a similar instrument called a "Deed of Trust" supported by a "Promissory Note", both of which are used in California and several other states.
It would probably be considered discrimination in most jurisdictions to deny any individual(s) a traditional 30 year fixed conforming loan based solely on "Age" even though the odds of a 90 year old paying the debt off in full are as favorable as "Mitt" biting his upper lip profusely and without hesitation, reluctantly disclosing the true facts about his MA Healthcare Program and how closely it does indeed resemble Pres. Obama's which is scheduled to be rolled out in it's entirety within the next few years.
In California to my knowledge it would be considered discrimination, however, different states may have conflicting laws or statutes and moreover, applicable federal laws may either support or override state and or local jurisdiction.
I'm not an attorney nor have I ever played one, except for that one time in Rio when I accidentally fell out of that "Sky Diving" plane at roughly 10,000 without a parachute....Or was I nudged out?... I Wonder?...In any event, I thought the sign said "Take this plane to go SCUBA DIVING", so after all was said and done, I sued myself for Negligence, Pain & Suffering, Punative Monetary Damages, and a free trip to the "Eye Doctor" and WON.
But seriously, check with a bar member for more precise info.