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Abstract
Objective: To determine whether metformin is associated with a lower incidence of dementia than sulfonylureas.
Methods: This was a retrospective cohort study of US veterans ≥65 years of age with type 2 diabetes who were new users of metformin or a sulfonylurea and had no dementia. Follow-up began after 2 years of therapy. To account for confounding by indication, we developed a propensity score (PS) and used inverse probability of treatment weighting (IPTW) methods. Cox proportional hazards models estimated the hazard ratio (HR) of incident dementia.
Results: We identified 17,200 new users of metformin and 11,440 new users of sulfonylureas. Mean age was 73.5 years and mean HbA1c was 6.8%. Over an average follow-up of 5 years, 4,906 cases of dementia were diagnosed. Due to effect modification by age, all analyses were conducted using a piecewise model for age. Crude hazard ratio [HR] for any dementia in metformin vs sulfonylurea users was 0.67 (95% confidence interval [CI] 0.61–0.73) and 0.78 (95% CI 0.72–0.83) for those <75 years of age and ≥75 years of age, respectively. After PS IPTW adjustment, results remained significant in veterans <75 years of age (HR 0.89; 95% CI 0.79–0.99), but not for those ≥75 years of age (HR 0.96; 95% CI 0.87–1.05). A lower risk of dementia was also seen in the subset of younger veterans who had HbA1C values ≥7% (HR 0.76; 95% CI 0.63–0.91), had good renal function (HR 0.86; 95% CI 0.76–0.97), and were white (HR 0.87; 95% CI 0.77–0.99).
Conclusions: After accounting for confounding by indication, metformin was associated with a lower risk of subsequent dementia than sulfonylurea use in veterans <75 years of age. Further work is needed to identify which patients may benefit from metformin for the prevention of dementia.
GLOSSARY
- ADA=
- American Diabetes Association;
- CI=
- confidence interval;
- eGFR=
- estimating glomerular filtration rate;
- HbA1c=
- hemoglobin A1c;
- HR=
- hazard ratio;
- ICD-9=
- International Classification of Diseases–9;
- IPTW=
- inverse probability of treatment weighting;
- MCI=
- mild cognitive impairment;
- PS=
- propensity score;
- VA=
- Veterans Administration;
- VaD=
- vascular dementia
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Supplemental data at Neurology.org
Editorial, page 1848
- Received December 20, 2016.
- Accepted in final form August 1, 2017.
- © 2017 American Academy of Neurology
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