Use of metformin, DPP4 inhibitors, GLP1 analogs, and SGLT2 inhibitors were associated with lower odds of dementia after multible adjustments (ORs of 0.94 (95% confidence interval (CI): 0.89-0.99), 0.80 (95% CI 0.74-0.88), 0.58 (95% CI: 0.50-0.67), and 0.58 (95% CI: 0.42-0.81), respectively), with a gradual decrease in odds of dementia for each increase in daily defined dose.
Lower risk of dementia was particularly noticeable in all of the combination therapy groups and especially lower in the combination therapy group treated with dipeptidyl peptidase 4 inhibitor (aHR 0.48, 95% CI 0.45-0.51).
Individuals aged ≥65 years on metformin + pioglitazone had a significantly lower risk of dementia compared with those on metformin + sulfonylurea (HR 0.56; 95% CI 0.34, 0.93), and a lower, but insignificant, risk of dementia compared with those on other metformin-based dual regimens (i.e. metformin + acarbose, metformin + meglitinide, metformin + insulin or metformin + dipeptidyl peptidase 4 inhibitors).
These associations implicate genes related to apoptosis (HRK), development (WIF1), oxidative stress (MSR3B), ubiquitination (FBXW8) and neuronal migration (ASTN2), as well as enzymes targeted by new diabetes medications (DPP4), indicating new genetic influences on hippocampal size and possibly the risk of cognitive decline and dementia.