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Fasting Glucose Estimates Absolute Risk for CVD

Mar 26, 2019
 

Author: Steve Freed, R.PH., CDE


Monitoring glucose in midlife may help prevent future cardiovascular disease, according to a study published in Diabetes Care.

In this study and the Korean Heart Study, the authors sought to determine whether fasting glucose can be used to estimate the long-term absolute risk for cardiovascular disease (CVD). Among the 19,630 participants in this current study, including 32% African Americans and 56% women, CVD risk through 85 years of age was 15.3% among women with fasting glucose levels <90 mg/dL.(5.0 mmol/L) and 38.6% among those at or above the threshold for diabetes. The values were 21.5% and 47.7% in men. In men, fasting glucose levels approaching the diabetes threshold ((112 mg/dL–125 mg/dL (6.3–6.9 mmol/L)) were associated with an elevated risk of CVD. However, this was not the case among women. Glucose increases in midlife had a greater impact on CVD risk when those increases led to crossing the threshold to diabetes when compared with increases where the final level was still below the threshold.

 

They pooled data from seven observational cohorts of U.S. black and white men and women followed from 1960 to 2015. They categorized FG as follows, <90, 90-100, 102-108, 114-124mg/dL. (<5.0, 5.0-5.5, 5.6-6.2, 6.3-6.9 mmol/L), and diabetes (FG >125mg//dL.(≥7.0 mmol/L) or use of diabetes medications. CVD was defined as fatal/nonfatal coronary heart disease and fatal/nonfatal stroke. They estimated the risk of CVD by FG category at index age 55 years using a modified Kaplan-Meier survival analysis, adjusted for the competing risk of non-CVD death. They also assessed risk for incident CVD according to change in FG before 50 years of age, specifically among the categories <100mg/dl, 100-124mg/dL.(<5.6 mmol/L, 5.6-6.9 mmol/L,) and diabetes.

This sample included 6,197 African Americans and 11,015 women without a prior CVD event. Risk for CVD through 85 years of age ranged from 15.3% (<90mg/dL or 5.0 mmol/L) to 38.6% (diabetes levels) among women and from 21.5% (90-100mg/dL or 5.0-5.5 mmol/L) to 47.7% (diabetes levels) among men. An FG of 114-125mg/dL (6.3-6.9 mmol/L) was associated with higher long-term CVD risk compared with the lowest FG among men, but not women. Increases in glucose during midlife with conversion to diabetes were associated with higher cardiovascular risk (1.3- to 3.6-fold) than when increasing glucose below the diabetes threshold.

In the Korean Heart Study, it is well-established that type 2 diabetes is associated with a marked increase in the risk of cardiovascular disease (CVD) and ischemic heart disease (IHD)). Studies suggest that atherosclerosis develops before the onset of clinical diabetes. Supporting this possibility, many studies have reported that impaired glucose tolerance (IGT) is associated with increased cardiovascular morbidity and mortality. However, the association between impaired fasting glucose (IFG) and risk of CVD and/or IHD remains unclear. Although some studies have reported that IFG was associated with a greater risk of IHD/CVD in women than in men, others have reported similar risks for men and women.

There has also been considerable debate regarding the threshold glucose level associated with increased CVD risk. In 2003, the American Diabetes Association (ADA) lowered the fasting plasma glucose (FPG) cutoff point for IFG from 110 to 100 mg/dL (6.1 mmoL/L to 5.5 mmol/L). Some studies have reported that FPG levels of 110–125 mg/dL  (6.1 mmol/L–6.94 mmol/L) were associated with significantly higher rates CVD morbidity or mortality, but that FPG levels of 100–109 mg/dL (5.5 mmol/L–6.05 mmol/L) were not. However, other investigators reported that the relationship between CVD risk and fasting glucose was continuous or J-shaped rather than showing a threshold effect at high glucose levels.

In conclusion, the study showed that IFG, defined as FPG levels of 100–125 mg/dL (100 mmol/L–6.94 mmol/L), is associated with increased risk of CVD (including IHD and ischemic stroke) in the Korean population. This association is independent of other conventional risk factors in men but not in women. Further studies are needed to identify subgroups with IFG for whom prevention efforts in reducing cardiovascular events are cost-effective.

This study provides further evidence that if one can avoid prediabetes, one may be able to stave off cardiovascular disease. Prediabetes should serve as a red flag to closely monitor a patient’s glucose levels to try to prevent diabetes through lifestyle interventions like better diet and increased physical activity, and, if necessary, with pharmacologic therapies. Because prediabetes increases the risk for CVD, we should be treating prediabetes more aggressively with more than just lifestyle changes.

Practice Pearls:

  • Middle-age individuals with diabetes have high long-term absolute risk for CVD.
  • The study shows the importance of preventing not just diabetes but prediabetes to reduce the risk of CVD.
  • These data strongly support the importance of glucose monitoring in midlife for CVD prevention.

References:

Diabetes Care 2019 Jan; dc181773.https://doi.org/10.2337/dc18-1773

Diabetes Care. 2013 Feb; 36(2): 328–335.