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Metformin linked to lower dementia risk in black patients



Black individuals who develop type 2 diabetes are more likely than their white counterparts to develop dementia. Now, findings from a new study point to a possible preventive strategy: Putting older patients on metformin when they are diagnosed could reduce their risk for dementia by as much as 40%, whereas sulfonylureas do not seem to have such an effect.

The researchers did not examine cause and effect, so their findings are not conclusive, and very few women were included in the study. Still, the authors said that their data showing a 29% lower risk of dementia associated with metformin use in black patients aged 65-74 years, and a 40% lower risk in those aged 50-64 years, suggested that “this inexpensive, widely available treatment could be broadly prescribed to substantially reduce the risk of dementia in younger [black] patients with [type 2 diabetes]” (Ann Fam Med. 2019;17:352-62).

Previous findings have suggested that black patients with type 2 diabetes face a 10%-18% higher risk of dementia, compared with white patients (Diabetes Care. 2014; 37[4]:1009-15). Another study linked type 2 diabetes in middle-aged black patients to a 41% decrease in cognition per test results over 14 years. There was no such decrease in white patients (Neuroepidemiology. 2014;43[3-4]: 220-7).

For the new study, researchers led by Jeffrey F. Scherrer, PhD, of Saint Louis University tracked 73,761 patients aged 50 years or older from 2000-2001 (when they were free of dementia and not taking diabetes) to 2015. Among the patients, 86% were white and 14% were black. In the white and black groups, 97% and 95% were men, respectively, and 61% and 55% were obese, respectively.

All participants began metformin (76%) or sulfonylurea (24%) monotherapy after the baseline period. Guidelines recommend metformin as a first-line treatment for type 2 diabetes, whereas sulfonylureas are considered second-line drugs that should be added to metformin.

After adjustment for confounders such as socioeconomic status and other medical conditions, the researchers found a significantly lower risk of dementia in black patients who took metformin, compared with those taking a sulfonylurea (hazard ratio, 0.73; 95% confidence interval, 0.6-0.89). There was no difference between the drugs among white patients (HR, 0.96; 95% CI, 0.9-1.03, both P = .008)

The results were not statistically significant among age groups, but there were trends. In black patients, the dementia-lowering benefit was largest among those aged 50-64 years (HR, 0.6; 95% CI, 0.45-0.81), followed by those aged 65-74 years (HR, 0.71; 95% CI, 0.53-0.94), and there was no benefit among those aged at least 75 (HR, 1.17; 95% CI, 0.73-1.85) all P = .055. There was a slight benefit among white patients in one of the age groups – 65-74 years (HR, 0.9; 95% CI, 0.82-0.99; P = .315).

The authors suggested that the findings could have been the result of an effect of metformin to reduce vascular disease and chronic inflammation in black patients.

They also noted that further research is needed to identify the demographic and clinical subgroups in which metformin is most strongly associated with a reduction in the risk of dementia. In addition, they emphasized that clinical trials are needed to confirm the study findings.

The National Institutes of Health funded the study. The authors report no relevant disclosures.

SOURCE: Scherrer JF et al. Ann Fam Med. 2019;17:352-62.

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