No comments about the truth of the prejudice against older programmers, but this study does not prove anything. There is a huge self-selection bias going on her

No comments about the truth of the prejudice against older programmers, but this study does not prove anything. There is a huge self-selection bias going on here, as not all programmers go on stack overflow and certainly not all programmers answer questions on stack overflow. There could be many older programmers who have not kept up to date with the latest skills and best practices, who know the only reason why their job is secure at BigCorp is because their code is so bad/intentionally obfuscated that no one else can read it, who don't answer questions on stack overflow.