title: Differing effects of metformin on glycemic control by race-ethnicity.
abstract: BACKGROUND
  Metformin is considered first-line treatment for type 2 diabetes mellitus. However, little is known about its effects in African American individuals.
  
  
  OBJECTIVE
  The objective of the study was to assess whether metformin's effect on glycemic control differs by race-ethnicity Design: Electronic health records were used to identify adults who had a diagnosis of diabetes, two or more fills of metformin, and two or more glycated hemoglobin (HbA1c) measurements. Pharmacy claims were used to estimate metformin exposure based on fill frequency and dose dispensed. Regression analyses modeled the relationship between metformin exposure and HbA1c levels. Analyses were stratified by race-ethnicity and baseline HbA1c values.
  
  
  METHODS
  The study was conducted at a large health system in southeast Michigan.
  
  
  METHODS
  Differences in HbA1c levels while on metformin were measured.
  
  
  RESULTS
  We identified 19 672 patients with diabetes taking metformin; 7429 were African American and 8783 were European American. Baseline HbA1c values in these two groups were 7.81% (61.8 mmol/mol) and 7.38% (57.1 mmol/mol), respectively. Compared with no use, metformin was associated with a 0.62% (6.8 mmol/mol) reduction in HbA1c; however, there was a significant difference by race-ethnicity (P < .001). Among African American individuals, metformin use was associated with a 0.90% (9.8 mmol/mol) reduction in HbA1c levels, whereas among European Americans, metformin was associated with a 0.42% (4.6 mmol/mol) reduction. Irrespective of baseline HbA1c, metformin use was associated with lower HbA1c levels in African American individuals.
  
  
  CONCLUSIONS
  African American individuals appear to have a better glycemic response to metformin when compared with European Americans. Further studies are needed to determine whether this translates to commensurate reductions in diabetes complications.
authors.affiliation: Center for Health Policy and Health Services Research (L.K.W., B.P., B.K.A., D.E.L.), Department of Internal Medicine (L.K.W., D.E.L.), Department of Public Health Sciences (E.L.P., K.E.W.), Henry Ford Health System, Detroit, Michigan 48202; and Departments of Medicine (E.G.B.) and Bioengineering and Therapeutic Sciences (E.G.B.), University of California, San Francisco, San Francisco, California 94143.
authors.forename: L Keoki
authors.initials: LK
authors.lastname: Williams
authors.forename: Badri
authors.initials: B
authors.lastname: Padhukasahasram
authors.forename: Brian K
authors.initials: BK
authors.lastname: Ahmedani
authors.forename: Edward L
authors.initials: EL
authors.lastname: Peterson
authors.forename: Karen E
authors.initials: KE
authors.lastname: Wells
authors.forename: Esteban
authors.initials: E
authors.lastname: González Burchard
authors.forename: David E
authors.initials: DE
authors.lastname: Lanfear
mesh_terms: D000328:Adult; D001741:Black or African American; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000208:ethnology*; D057286:Electronic Health Records; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D038321:Glycemic Index / Q000187:drug effects; D006801:Humans; D006943:Hyperglycemia / Q000188:drug therapy* / Q000208:ethnology*; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000009:adverse effects; D008297:Male; D008687:Metformin / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D044465:White People
chemical_list: D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D008687:Metformin; C517652:hemoglobin A1c protein, human