This is how that source handles age > 90 for DP3, they adjust the date of birth to 1800. A person with a record from 4 years ago who was 89 years old at the time would still have their actual birth year in the records from 4 years ago, so you could calculate that today they are 93 years old. The best way to think of it is someone who's age is >= 90 at the enrollment termination date gets an 1800 birth year. For additional context, please review the below chart.
