Prediabetes: A Prevalent and Treatable, but Often Unrecognized, Clinical Condition

Abstract

Type 2 diabetes mellitus (T2DM) affects more than 8% of the United States population.1 The onset of T2DM is gradual, with most individuals progressing through a state of pre-diabetes which is defined as impaired fasting glucose (IFG; plasma glucose of 100–125 mg/dl or 5.6–6.9 mmol/l) and/or impaired glucose tolerance (IGT; plasma glucose of 140–199 mg/dl or 7.8–11.0 mmol/l 2h after an oral load of 75g dextrose) and/or hemoglobin A1C 5.7–6.4%.2 According to a study of a nationally representative sample (n =1,547), an estimated 35% of the United States population suffers from pre-diabetes: 19% have IFG only, 5% have IGT only, and 10% have both IFG and IGT.3 Although individuals can spend years in a pre-diabetic state, an expert American Diabetes Association (ADA) panel estimated that up to 70% will eventually progress to T2DM.4 However, not all individuals with pre-diabetes progress at the same rate. A meta-analysis of prospective cohort studies showed that the annual incidence of diabetes in people with IGT, IFG, or both was 6.1%, 7.0%, and 14.0% respectively.5 The diagnosis of pre-diabetes presents healthcare providers with an opportunity to identify patients at increased risk for T2DM and to implement interventions that can delay or prevent T2DM and its complications.4 Unfortunately, this opportunity is often unrecognized, as an analysis of a nationally representative sample of patients with pre-diabetes (n=584) concluded that only 31.7%, 33.4%, 25.9% had been counseled about exercise, diet, or both, respectively by a doctor or health professional.3 Possible reasons for not counseling patients include lack of reimbursement, lack of resources, lack of time, and lack of skill.6, 7 However, individuals who have been counseled by their health-care provider to adopt a healthy lifestyle reported greater adherence to weight control and diet modification and had lower low density lipoprotein (LDL) cholesterol, lower body mass index (BMI), and higher high density lipoprotein (HDL) cholesterol.8 Still, it is unclear whether counseling sessions by a primary care provider in the outpatient setting are correlated with improvements in fasting plasma glucose in patients with pre-diabetes compared to similar patients who have not been counseled. While there is some evidence to suggest lifestyle counseling may be associated with self-reported changes in lifestyle behavior in overweight and obese adults with pre-diabetes and diabetes,9 other data suggest that lifestyle intervention programs that have been implemented in the outpatient healthcare setting have had an insignificant impact on fasting plasma glucose.6 Nevertheless, according to ADA guidelines there is clear evidence to support providing medical nutrition therapy as needed to patients with pre-diabetes.10 Given the high prevalence of pre-diabetes, it is important to understand the basic underlying pathophysiology and how lifestyle interventions can be implemented in the clinical setting to reduce a patient’s risk for developing T2DM.