title: Effect of Coffee Consumption on the Progression of Type 2 Diabetes Mellitus among Prediabetic Individuals.
abstract: BACKGROUND
  A previous large-scale cohort study investigated the relationship between coffee intake and the progression of diabetes mellitus in the United States. However, studies on the effects of coffee on diabetes are rare in South Korea. Therefore, this study assessed the amount and method of coffee intake in Koreans in order to determine if coffee intake has a prophylactic effect on diabetes progression.
  
  
  METHODS
  This study included 3,497 prediabetic patients from a single medical institution, with glycated hemoglobin levels ranging from 5.7% to 6.4%. Cross-tabulation and Kaplan-Meier survival analyses were performed to compare patients with and without diabetes progression based on the frequency and method of coffee intake. Cox proportional hazard analysis was performed to correct for confounding variables.
  
  
  RESULTS
  The observation period (mean±standard deviation) was 3.7±2.3 years. Kaplan-Meier survival analysis revealed that the risk of diabetes progression was lowest in patients who drank black coffee three or more times per day (P=0.036). However, correction for confounding variables in Cox proportional hazard analysis revealed that, while the risk was lower for the patients who typically consumed black coffee than for those who mixed creamer and sugar into their coffees, the difference was not significant.
  
  
  CONCLUSIONS
  The results of this study suggest that drinking coffee without sugar and creamer at least three times daily has the greatest preventive effect on diabetes onset.
authors.affiliation: Department of Family Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
authors.forename: Ji-Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Family Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
authors.forename: Mi-Kyeong
authors.initials: MK
authors.lastname: Oh
authors.affiliation: Department of Family Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
authors.forename: Jun-Tae
authors.initials: JT
authors.lastname: Lim
authors.affiliation: Department of Family Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
authors.forename: Haa-Gyoung
authors.initials: HG
authors.lastname: Kim
authors.affiliation: Department of Family Medicine, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
authors.forename: Won-Joon
authors.initials: WJ
authors.lastname: Lee
keywords: Coffee; Diabetes Mellitus; Glycated Hemoglobin; Prediabetic State