Are problems with the ear the cause of this (i.e., the Problem), or just another symptom of a broader problem? My impression from the article is the latter.
Seems like the obvious confounding factor is just aging: Old people have problems with hearing, and old people are also less likely to walk briskly. The subset of people with undiagnosed hearing problems probably aren't taking care of their health in general.
(Frankly, it is ridiculous to me that doctors go around saying that fixing your hearing will free up your brain will fix your life. Fix the thing that's dragging down an expensive system that's wired straight into the sensorium and yep, you'll fix your other expensive systems like the brain.)