“A study of more than 41,000 metformin users between the ages of 68 and 81 concluded that metformin reduced the likelihood of dementia, cardiovascular disease, cancer, frailty, and depression, and not by a small amount. In one group of already frail subjects, metformin use over the course of nine years reduced dementia by 4 percent, depression by 16 percent, cardiovascular disease by 19 percent, frailty by 24 percent, and cancer by 4 percent.22 In other studies, the protective power of metformin against cancer has been far greater than that.”