Statistical evidence of disparate impact is required to state a claim that an employer's policy had a disparate impact on older workers so long as the policy is not a sweeping disqualification.
http://media.ca8.uscourts.gov/opndir/18/08/164376P.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.