Fasting glucose levels and health risks
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Fasting Glucose Levels and Cardiovascular Disease Risk
Research consistently shows that both high and low fasting glucose levels are linked to increased health risks, especially for cardiovascular disease (CVD) and mortality. The relationship between fasting glucose and CVD risk often follows a J-shaped curve, meaning that both very low and high glucose levels are associated with higher risks, while a moderate range is safest Park2013Lee2020Yi2017+2 MORE.
High-Normal and Elevated Fasting Glucose: Increased CVD and Mortality Risk
Multiple large cohort studies have found that fasting glucose levels even within the high-normal range (typically 95–99 mg/dL or 5.3–5.5 mmol/L) are associated with a higher risk of CVD and all-cause mortality compared to lower-normal levels Park2013Shaye2012Yi2017+3 MORE. As fasting glucose rises above 100 mg/dL, the risk for CVD, ischemic heart disease, myocardial infarction, and stroke increases further, even in people without diabetes Park2013Shaye2012Yi2017+4 MORE. This risk is independent of other factors like age, sex, blood pressure, and cholesterol Shaye2012Bjørnholt1999.
Low Fasting Glucose: Not Always Protective
Low fasting glucose levels, particularly below 70–80 mg/dL (3.9–4.4 mmol/L), are also linked to increased risks of all-cause mortality and stroke Park2013Liao2019Lee2020+2 MORE. A meta-analysis found that people with fasting glucose below 4.0 mmol/L (about 72 mg/dL) had higher risks of death, major cardiovascular events, and stroke compared to those with normal levels . This J-shaped risk curve means that both ends of the glucose spectrum can be harmful Park2013Lee2020Yi2017+2 MORE.
Fasting Glucose and Stroke Risk
A dose-response meta-analysis shows that stroke risk is lowest when fasting glucose is between 70–100 mg/dL (3.9–5.6 mmol/L), and increases as glucose levels rise above this range Park2013Yi2017Shi2020. Even in non-diabetic individuals, higher fasting glucose is linked to greater stroke risk Park2013Yi2017Shi2020.
Fasting Glucose and Cancer Mortality
Recent research also suggests a J-shaped relationship between fasting glucose and cancer mortality, with both impaired fasting glucose and diabetes associated with higher cancer death rates compared to normal glucose levels .
Special Populations: Older Adults and Hemodialysis Patients
In older adults with diabetes, the optimal fasting glucose range for the lowest risk of death and cardiovascular events may be slightly higher (95–124 mg/dL), especially for those with multiple health conditions . Among patients with diabetes on hemodialysis, the lowest mortality risk is seen with fasting glucose between 80–100 mg/dL, with higher and lower levels both increasing risk .
Changes in Fasting Glucose Over Time
Rising fasting glucose levels over time, even within the non-diabetic range, are associated with increased risks of myocardial infarction, stroke, and all-cause mortality . This highlights the importance of monitoring and managing fasting glucose, even before diabetes develops.
Conclusion
Both high and low fasting glucose levels are linked to increased risks of cardiovascular disease, stroke, cancer mortality, and all-cause mortality. The safest range for fasting glucose appears to be relatively narrow, generally between 80–99 mg/dL (4.4–5.5 mmol/L) for most adults, though slightly higher targets may be appropriate for older adults with diabetes or multiple comorbidities. Regular monitoring and early intervention for abnormal fasting glucose can help reduce long-term health risks.
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