In contrast to the ADA, the US Preventive Services Task Force (USPSTF) has less-specific recommendations for abnormal glucose and diabetes screening (Table 4). The USPSTF recommends that clinicians refer patients with abnormal blood glucose levels to intensive behavioral counseling interventions to promote a healthful diet and physical activity.13
After initial screening tests are performed, the ADA, USPSTF, and CDC recommend further testing for patients at high risk of developing prediabetes. Fasting blood glucose, A1C, and an oral glucose tolerance test with a 75-g glucose solution are all options as first-line screening tests for diagnosis of diabetes and prediabetes.2,13 Many providers prefer testing a patient's A1C, which is convenient and does not require fasting.
In a large prospective study of more than 18,000 patients, A1C-based testing was the most specific for diagnosing prediabetes.14 From a standpoint of limiting long-term complications and mortality related to type 2 diabetes, using A1C may yield better risk discrimination for comorbidities such as chronic kidney disease, cardiovascular disease, peripheral artery disease, and all-cause mortality versus fasting glucose concentration-based definitions (P < .05). This increase in risk discrimination for clinical complications should be considered when performing diagnostic testing to screen patients for prediabetes.
Lifestyle modification is a fundamental aspect of prediabetes management, and includes healthful nutrition, increased activity, and if applicable, smoking cessation counseling. Weight management is important in patients with prediabetes who are overweight or obese. Weight loss can delay progression from prediabetes to type 2 diabetes.14,15 The ADA recommends a combination of activity and diet modification (specifically, reducing calorie intake) to attain moderate persistent weight loss. Although the ADA does not endorse a “best diet,” the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and plant-based diets all are acceptable.2 Patients should avoid foods rich in sugar, including sugar-sweetened beverages and candy, as they often replace healthful, more nutrient-dense choices.2 Carbohydrate intake should consist of vegetables, whole grains, fruits, legumes, and low-fat dairy products. Encourage patients to make healthful food choices and control portion sizes. New studies have found that diets rich in whole grains, nuts, berries, plain yogurt, coffee, and tea are associated with reduced diabetes risk.2
Encourages patients to be physically active to maintain significant weight loss and prevent the progression from prediabetes to type 2 diabetes. The US Department of Health and Human Services, ADA, and the American College of Sports Medicine physical activity guidelines suggest that as a general health measure, adults over age 18 years should engage in a minimum of 150 minutes/week of moderate-intensity aerobic physical activity, or 75 minutes/week of vigorous-intensity aerobic physical activity. Adults also are encouraged to participate in muscle-strengthening activities involving major muscle groups two or more times per week.16 For patients over age 65 years, those who are disabled, or those who may be otherwise unable to perform strenuous activities, any low-impact physical activity is encouraged. Avoiding sedentary periods also may help to prevent the progression of prediabetes to type 2 diabetes and improve glycemic control among at-risk patients.2 Encourage patients to break up sedentary periods with activity every 30 minutes—for example, by standing, walking, stretching, or other light physical activity.16 Based on these findings, the ADA recommends an intensive behavioral style intervention program modeled on the National Diabetes Prevention Program that encompasses many of the above characteristics, which can help patients lose 7% of their body weight over 1 year and then maintain that weight loss.2
NATIONAL DIABETES PREVENTION PROGRAM
The Diabetes Prevention Program study aimed to determine the most effective method of preventing progression to type 2 diabetes: a lifestyle change intervention or metformin.8 The lifestyle interventions were improving diet choices, reducing calories from fat, increasing physical activity to a minimum of 150 minutes per week, and an overall 7% weight loss goal for each participant. After nearly 3 years of data collection, the intensive lifestyle intervention group had a reduced incidence of type 2 diabetes by 58% and the metformin group by 31%, compared with 17% in the placebo group.8 A 10-year follow-up study showed the original lifestyle intervention group had a continued decreased incidence of diabetes by 34%, and the metformin group had a decreased incidence by 18%.17 This showed that even participants who discontinued healthful lifestyle modifications had lasting health benefits remained from the initial intervention.
The National Diabetes Prevention Program is a well-validated community-based program modeled after the Diabetes Prevention Program study but simplified for community implementation. The 1-year program consists of at least 16 sessions over the first 6 months followed by at least monthly sessions in the second 6 months. The program's goals mirror those of the study, focusing on reducing caloric intake by reducing fat intake, increasing physical activity to at least 150 minutes per week, and achieving greater than 7% weight loss by the end of the program.18 By creating a constant, regular, and supportive group environment, the program helps participants maintain healthful lifestyle choices. One of the program's main goals is for participants to apply the knowledge acquired from the program to successfully lead a more healthful lifestyle.
To qualify for participation in the program, participants must have:
- Body mass index (BMI) of at least 24 (or at least 22 if self-identified as Asian)
- One of the following blood glucose test results:
- A1C of 5.7% to 6.4%
- Fasting plasma glucose of 100 to 125 mg/dL
- 2-hour post glucose of 140 to 199 mg/dL after 75-g glucose load
- No previous diagnosis of type 1 or type 2 diabetes (patients may have had gestational diabetes)
- Exclusion criteria: Current diagnosis of diabetes or current insulin use or end-stage renal disease.18 Fully recognized programs are led by CDC-certified lifestyle coaches and follow the CDC-approved curriculum. To maintain full recognition, programs must meet CDC requirements and undergo yearly evaluations.
The cost of participating in the National Diabetes Prevention Program is covered under some insurance plans. However, in 2018 Medicare began providing the program as a mandated covered service. Patient copays and deductibles may still apply, including under Medicare.
MEDICAL INTERVENTIONS FOR PREDIABETES
Pharmacologic therapy also has proven effective in preventing or delaying progression to type 2 diabetes.2 The ADA suggests considering pharmacologic therapy to treat prediabetes for patients with one or more of the following:
- BMI of 35 or greater
- age under 60 years
- past medical history of gestational diabetes
- increasing A1C levels despite lifestyle intervention
- A1C greater than 6%.2
Compared with other drugs, metformin has shown the best long-term safety profile and strongest evidence for preventing diabetes.18 However, one study found that metformin is rarely prescribed among working-age adults ages 19 to 58 years who had prediabetes.19 Why metformin is not used more often is unclear but we recommend that clinicians use metformin as a first-line drug in patients with prediabetes.
Other medications may be helpful. Acarbose, an alpha glucosidase enzyme inhibitor, also has proven effective in reversing impaired glucose tolerance among patients with prediabetes.20 However, this treatment can be poorly tolerated due to its gastrointestinal (GI) adverse reactions. Metformin and acarbose also may provide additional cardiovascular benefit for patients with prediabetes and type 2 diabetes who are overweight or obese.21
Studies have shown that orlistat, a lipase inhibitor, reduced glucose levels among obese patients with impaired glucose tolerance.11 Available over-the-counter under the brand name Alli, this medication has limited use due its poorly tolerated GI adverse reactions.
Other medications, such as glucagon-like peptide 1 (GLP-1) receptor agonists and thiazolidinediones, also may be helpful in treating prediabetes; however, their high cost may be a limiting factor.10,22 Weight-loss medications including phentermine-topiramate have been shown to produce significant weight loss and reduce progression to type 2 diabetes in patients who are overweight or obese.23
In an ethnically diverse study population, bariatric surgery resulted in significant long-term weight loss and lower fasting plasma glucose levels over a 3-year postoperative period.12 A recent study conducted in Sweden found that bariatric surgery greatly reduced the risk of microvascular complications at baseline among patients with prediabetes.24 Though this study suggests that bariatric surgery reduces risk among patients with prediabetes, it does not endorse the surgery as a treatment for prediabetes; rather, it emphasizes the need for developing nonsurgical treatments to reduce risk in at-risk patients. Although the ADA has not made an exact recommendation for bariatric surgery in patients with prediabetes, consider this intervention in patients with well-controlled type 2 diabetes and a BMI of 40 or greater.2 Good evidence supports bariatric surgery for preventing the progression of diabetes in patients with prediabetes.25
The ADA recommends vigilance in screening and treatment for cardiovascular disease among patients with prediabetes. Patients in this at-risk group often have hypertension and/or dyslipidemia and are at increased for cardiovascular disease, thus emphasizing the importance of early screening and treatment of cardiovascular diseases among these patients.2
Clinicians can address the public health epidemic of diabetes and prediabetes. Screening for type 2 diabetes is key to preventing associated comorbidities and complications. Consider using the CDC's prediabetes screening test, testing glucose, and referring patients with prediabetes to a diabetes prevention program.1,3,5 If there are no National Diabetes Prevention Programs locally, consider becoming a certified lifestyle coach through the CDC.
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prevention programs in US settings: a systematic review and meta-analysis. PLoS Med
16. Colberg SR, Albright AL, Blissmer BJ, et al. Exercise and type 2 diabetes
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prevention: an intent-to-treat analysis of the DPP/DPPOS. Diabetes Care
19. Moin T, Li J, Duru OK, et al Metformin prescription for insured adults with prediabetes
from 2010 to 2012: a retrospective cohort study. Ann Intern Med
20. Chiasson JL, Josse RG, Gomis R, et al STOP-NIDDM Trial Research Group. Acarbose treatment and the risk of cardiovascular disease and hypertension in patients with impaired glucose
tolerance: the STOP-NIDDM trial. JAMA
21. Lamanna C, Monami M, Marchionni N, Mannucci E. Effect of metformin on cardiovascular events and mortality: a meta-analysis of randomized clinical trials. Diabetes Obes Metab
22. Le Roux CW, Astrup A, Fujioka K, et al 3 years of liraglutide versus placebo for type 2 diabetes
risk reduction and weight management in individuals with prediabetes
: a randomised, double-blind trial. Lancet
23. Garvey WT, Ryan DH, Henry R, et al Prevention of type 2 diabetes
in subjects with prediabetes
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24. Carlsson S, Andersson T, Ahlbom A. Prevalence and incidence of diabetes
mellitus: a nationwide population-based pharmaco-epidemiological study in Sweden. Diabet Med
25. Busetto L. Timing of bariatric surgery in people with obesity and diabetes
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Keywords:Copyright © 2018 American Academy of Physician Assistants
diabetes; type 2; public health; prediabetes; National Diabetes Prevention Program; glucose