The paper certainly has its limitations. Only 61 participants, with almost nobody between 30 and 50, so we shouldn’t read the age trend as a decline across lifespan. What’s more interesting than the title suggests (and I find the title forcing the conclusion a bit) is that the attention measures were not linked to age or the brain patterns at all.
Then again, i'm 45 and I've been losing my keys and my IDs since I was 20