This is from YOUR source:
In 1990, the FAA contracted with Hilton Systems,
Incorporated, for a study of accident rates, flying experience, and age. Accident rates for
the period 1976 through 1988 were analyzed for pilots holding Class 1, 2, or 3 medical
certificates and operating under Parts 91, 121, or 135. Kay, Hillman, Hyland, Voros,
Harris and Deimler (1994) reported "… no hint of an increase in accident rate for pilots
of scheduled air carriers as they neared the age of 60”
You need to read deeper. The CAMI reports point out the flawed logic in the Hilton Systems study.