Fascinating piece, Emily. The authors' abstract state, inter-alia: "These results thus suggest that education has no substantial role (direct or mediated) in aging-related changes in cognition".

We are not told if some or all of the participants engaged in consistent informal education during the study period.

Although I have no major references at this time to sustain this point, I believe one's basic education up to Doctorate level and even beyond is insufficient to wade off the speed of cognitive decline as one grows old.

What can help is continuous, informal, rigorous intellectual pursuit in addition of course to other factors like healthy diet, exercise, etc.