INS and type 2 diabetes mellitus: The included seven studies adjusted for potential confounders, which included age [59, 61–65], gender [59–65], education [60, 62, 63, 65], income [61–63], health status [63], health insurance status [61, 64], years lived with T2DM [59, 60], self-efficacy [60], insulin use [59, 64], number of medications [59, 64], number of health conditions, and race/ethnicity [59, 63–65].