Fasting glucose levels and health outcomes
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Fasting Glucose Levels and All-Cause Mortality
Research consistently shows a J-shaped relationship between fasting glucose levels and all-cause mortality. Both very low and high fasting glucose levels are linked to increased mortality risk. The lowest mortality rates are generally observed in individuals with fasting glucose levels in the range of 80–99 mg/dL (4.4–5.5 mmol/L) 2579. For example, in a large Korean cohort, mortality risk increased with fasting glucose above 100 mg/dL, and the association was stronger in younger adults . Similarly, impaired fasting glucose (100–125 mg/dL) and diabetes (≥126 mg/dL) were associated with higher all-cause and cancer mortality compared to normal fasting glucose .
Low Fasting Glucose and Health Risks
Low fasting glucose levels, particularly below 4.0 mmol/L (about 72 mg/dL), are associated with increased risks of all-cause mortality, major cardiovascular events, and stroke in people without diabetes or cardiovascular disease 15. However, less stringent low fasting glucose levels (e.g., <4.6 mmol/L or about 83 mg/dL) do not show this increased risk . In postmenopausal women, low fasting glucose was not significantly associated with higher cardiovascular disease or mortality risk, except for a possible increase in heart failure risk, which was not statistically significant .
High Fasting Glucose and Cardiovascular Disease
Elevated fasting glucose, even within the high-normal range (95–99 mg/dL), is independently associated with increased risk of cardiovascular disease (CVD) in people without diabetes 4567+2 MORE. As fasting glucose rises above 100 mg/dL, the risk for CVD, ischemic heart disease, myocardial infarction, and stroke increases progressively 4567+1 MORE. Changes in fasting glucose status over time, such as moving from normal to impaired or diabetic fasting glucose, further increase the risk of myocardial infarction, stroke, and all-cause mortality .
Fasting Glucose Targets in Older Adults with Diabetes
In older adults with type 2 diabetes, the relationship between fasting glucose and health outcomes is also J-shaped. The lowest risks of mortality and cardiovascular events are seen with fasting glucose levels between 95–124 mg/dL. Notably, low fasting glucose (<95 mg/dL) is linked to increased cardiovascular risk, especially in those with multiple comorbidities, suggesting that less stringent glucose targets may be safer for older adults with complex health profiles .
Fasting Glucose and Pregnancy Outcomes
In pregnant women with hyperglycemia, elevated fasting glucose is more strongly associated with adverse maternal and neonatal outcomes than elevated post-load glucose. The risk is highest when both fasting and post-load glucose levels are elevated, but even fasting hyperglycemia alone increases the risk of complications such as Caesarean section and neonatal intensive care admission .
Global Burden of Disease from High Fasting Glucose
High fasting plasma glucose is a major global public health problem, contributing significantly to the burden of disease worldwide. It is an independent risk factor for several adverse health outcomes, including cardiovascular disease and mortality, and its impact has increased over recent decades .
Conclusion
Both low and high fasting glucose levels are linked to adverse health outcomes, with the lowest risks generally found in the mid-normal range (about 80–99 mg/dL). High fasting glucose, even within the normal range, increases the risk of cardiovascular disease and mortality, while very low fasting glucose can also be harmful, especially in people without diabetes. In older adults and pregnant women, individualized fasting glucose targets may help minimize health risks. Monitoring and maintaining fasting glucose within an optimal range is important for reducing the risk of major health outcomes.
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