title: Predictors of HbA1c levels in patients initiating metformin.
abstract: The aim was to assess demographic and clinical factors as predictors of short (6 months) and long term (18 months) HbA1c levels in diabetes patients initiating metformin treatment.
  
  
  
  We conducted a cohort study including type 2 diabetes patients who received their first metformin prescription between 2007 and 2013 in the Groningen Initiative to Analyze Type 2 Diabetes Treatment (GIANTT) database. The primary outcome was HbA1c level at follow-up adjusted for baseline HbA1c; the secondary outcome was failing to achieve the target HbA1c level of 53 mmol/mol. Associations were analyzed by linear and logistic regression. Multiple imputation was used for missing data. Additional analyses stratified by dose and adherence level were conducted.
  
  
  
  The cohort included 6050 patients initiating metformin. Baseline HbA1c at target consistently predicted better HbA1c outcomes. Longer diabetes duration and lower total cholesterol level at baseline were predictors for higher HbA1c levels at 6 months. At 18 months, cholesterol level was not a predictor. Longer diabetes duration was also associated with not achieving the target HbA1c at follow-up. The association for longer diabetes duration was especially seen in patients starting on low dose treatment. No consistent associations were found for comorbidity and comedication.
  
  
  
  Diabetes duration was a relevant predictor of HbA1c levels after 6 and 18 months of follow-up in patients initiating metformin treatment. Given the study design, no causal inference can be made. Our study suggests that prompt treatment intensification may be needed in patients who have a longer diabetes duration at treatment initiation.
authors.affiliation: a Unit of Pharmacotherapy and Pharmaceutical Care, Department of Pharmacy , University of Groningen , Groningen , The Netherlands.|b School of Pharmacy , Institut Teknologi Bandung , Bandung , Indonesia.
authors.forename: Doti P
authors.initials: DP
authors.lastname: Martono
authors.affiliation: c Unit of Pharmacoepidemiology and Pharmacoeconomics, Department of Pharmacy , University of Groningen , Groningen , The Netherlands.
authors.forename: Eelko
authors.initials: E
authors.lastname: Hak
authors.affiliation: d Department of Clinical Pharmacy and Pharmacology , University of Groningen, University Medical Center Groningen , Groningen , The Netherlands.
authors.forename: Hiddo
authors.initials: H
authors.lastname: Lambers Heerspink
authors.affiliation: a Unit of Pharmacotherapy and Pharmaceutical Care, Department of Pharmacy , University of Groningen , Groningen , The Netherlands.|d Department of Clinical Pharmacy and Pharmacology , University of Groningen, University Medical Center Groningen , Groningen , The Netherlands.
authors.forename: Bob
authors.initials: B
authors.lastname: Wilffert
authors.affiliation: d Department of Clinical Pharmacy and Pharmacology , University of Groningen, University Medical Center Groningen , Groningen , The Netherlands.
authors.forename: Petra
authors.initials: P
authors.lastname: Denig
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000453:epidemiology; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008297:Male; D008687:Metformin / Q000627:therapeutic use*; D008875:Middle Aged
chemical_list: D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D008687:Metformin
keywords: Antidiabetic agents; Glucose-lowering therapy; Glycemic control; HbA1c; Metformin; Pharmacoepidemiology; Type 2 diabetes mellitus