Thank you. FYI, "reduced insulin sensitivity" results in excess insulin production. If the cells are less sensitive to insulin, the body "shouts a little louder" (secretes more insulin) in order to MAKE the cells open up to glucose.
Apparently these researchers in Sweden did not test insulin levels; if they had, they might have "tied" the smaller brain size and deteriorated language skills to elevated insulin rather than to the insulin sensitivity.
"… in elderly whose insulin sensitivity was still high [in other words, the pancreas was not over-secreting insulin], the brains were larger, and they had more gray matter in regions that are important for language skills…"