Were you actively trying to keep brain in shape ? As a medic (neurology is not my field though) I am interested if it is possible to keep brain in shape by "mind exercises" or it is urban myth.
This is what scared me off from career switches in general not just coding, and still gives me air of uncertainty. I've read too many stories like this for my own good or bad. Sending 800 applications is like full time, unpaid labor in itself.
IMHO the catch is that older people (teachers) translate their experience to younger (students). Teenagers are just naturally better at multitasking because they are yet to be affected by brain ageing. And school personnel can't imagine that someone can be using phone and listening at the same time. Now factor in that most 30+ crowd didn't grow up with smartphones, and teenagers are just used to doing stuff while being on phone from early age and we have an answer.
Did you face any age discrimination, e.g did you suspect that interviewers turned you down mostly because of age. Because I read a lot of stories like this.