[ilovesarah2012]

What is considerec “older”?

[BlueStateRightist]

It’s a gradient effect. Older fathers carry more mutations in their sperm. Therefore, risk is greater with 40 y.o. fathers when compared to 25 y.o. fathers, and much higher with 70 y.o. fathers, for example.

See http://www.cbsnews.com/8301-504763_162-57499075-10391704/older-fathers-more-likely-to-pass-on-autism-linked-genetic-mutations-to-offspring-study-shows/