AFAIK age groups are by 5 years. He held the record for the 100(-104) age group, now he holds it for the 105(-110) age group.
For example:
- athletics: https://en.wikipedia.org/wiki/List_of_world_records_in_maste...
- swimming: http://www.fina.org/content/masters-records
- cycling: http://www.uci.ch/mm/Document/News/News/16/60/58/20160502_Ma..., http://www.uci.ch/mm/Document/News/News/16/60/57/20160713_Ma...
- cross-country skiing: http://www.world-masters-xc-skiing.com/en/rules-of-competiti... (section 601. I can’t find world records here; maybe they do not keep them?)
- rowing ergometer: http://www.concept2.com/indoor-rowers/racing/records/world
Concept2 uses 10-year ranges for ergometer records, likely because of the smaller competitor pool.
Having age groups keeps older competitors interested in taking part in races.