People with diabetes mellitus (DM) have an increased probability of progressing to Alzheimer disease (AD) in the first year after a diagnosis of mild cognitive impairment (MCI), a study based on data from the AD Neuroimaging Initiative has shown. Propensity score matching was performed in 306 people with MCI, 102 of whom also had DM. By the end of the 12-month follow-up period, 8.82% of the DM group and 2.45% of the non-DM group had developed AD. The results suggest that people with DM could benefit from early therapeutic intervention — to improve glycaemic control, for example — following an MCI diagnosis.