You might look into taking a few supplements or improving the quality of your diet. We tend to become deficient in certain things as we get older and this can reduce our ability to focus. Reversing the deficiencies I suffered has helped me get my brain back, at least somewhat. It's not like I can calculate math problems faster than you can type them into a calculator these days like I once could, but I do function better than I did when I was really ill.
Walk more, eat better, consider switching to a kindle reader. Perhaps it is health related, as it largely was for me.
Best of luck.