The World Association of Veteran Athletes (WAVA) established age grading to aid performance comparisons across age and gender. The age grade for an athlete's performance at a given race distance is their finish time expressed as a percentage of the comparable (same age and gender) world record.
At the moment most races opt for allocation of age category prizes, jumping up in steps of 5 years: Sen, V35, V40, V45 etc. However, parkrun provides age grading for all its events. Race directors could save themselves a lot of results sorting headaches, and perhaps a bit of prize money, by awarding the best age grades achieved rather than the top within each age category. Maybe expect to see more age grade reporting in the future.