Twice a day, Craft's study participants used a device to inhale insulin. Nearly 75 percent of participants showed memory improvement, said Craft, who tracked results through cognitive tests and brain scans.
Hannibal's test results showed a 20 percent improvement in her memory.
"It's definitely a motivation for me to want to try to do this again," Hannibal said. "There may not be a breakthrough in my lifetime, but perhaps using these tools can prolong [progression] or even stave off [the disease]."
While early results of Craft's study suggest that insulin therapy seems promising, more long-term studies need to be done.
"The most effective way to improve insulin's function in the brain is exercise," Craft said. "It seems to have a bigger effect for women than for men, both in terms of its ability to protect against Alzheimer's disease and improve some aspects of thinking, like the ability to plan and organize."
Regardless of the studies, researchers say progress is slow. It is still unclear whether tools such as insulin therapy and other methods work to prevent or treat the disease, or prolong its progression.
But as more people with family history of the disease participate in studies, researchers find they can better track brain changes over time.
"We are just the early pioneers beginning to look decades before people become symptomatic," Wisconsin's Sager said.