Starting with the championship held in Ostend in June 2018 the players in the Seniors need to be born in 1957 or earlier.
The intention is to increase the age limit to 65.
As of January 1st 2018 the age limit goes up to 61 years. And then they add another year biannually, ending up at 65 years from January 1st 2024.
You can read more at this link