Having kids after 40 increases the risk by about the same percentage as one set of first cousins marrying within a family, which let’s face it a lot of desi families do to the extreme.. marrying first cousins off to each other generation after generation obviously multiplies that risk..
Comparing the risk of someone having a baby at 30 to that of a couple who themselves are cousins, parents are first cousins, grandparents are first cousins, great grandparents were first cousins etc. obviously the risk is far higher with the family which has only been marrying ‘inside’ for all those generations..