Millions of pre-diabetic Americans may be at increased risk of future stroke, say researchers at the University of California, San Diego School of Medicine in a new meta-analysis of epidemiological studies, but the precise degree of that threat is confounded by differing medical definitions and factors that remain unknown or unmeasured.
"The immediate implication of our findings is that people with pre-diabetes should be aware they are at increased risk of stroke, and that this condition is frequently associated with one or more major risk factors for cardiovascular disease," said Bruce Ovbiagele, MD, a professor of neurosciences at UC San Diego School of Medicine and the study's senior author. "Beyond that, there's a great need to further refine our understanding of that risk and how it's measured."
Writing in the June 8 online edition of the British Medical Journal, Ovbiagele and an international team of colleagues reviewed 15 qualifying prospective cohort studies that looked at the association between pre-diabetes and stroke risk. The studies, published between 2004 and 2011, involved 760,925 participants.
Pre-diabetes occurs when blood glucose levels are consistently higher than normal, but not yet high enough to be diagnosed as diabetes. The condition is widespread in the United States: An estimated 35 percent of American adults – approximately 79 million people – are believed to be pre-diabetic, and thus at greater risk of developing full-blown type-2 diabetes, which afflicts roughly 26 million Americans. Diabetes is the seventh leading cause of death in the U.S., and a major risk factor for heart disease and stroke, the first and fourth leading causes of death.
People with pre-diabetes typically have the same risk factors for cardiovascular disease as people with type 2 diabetes – specifically, high blood pressure, high cholesterol levels and obesity – but the condition's effect on future stroke risk has not been established.
Ovbiagele and colleagues found that an association between future stroke risk and pre-diabetes depended upon the definition of the latter. To determine whether someone has pre-diabetes, blood glucose levels are typically measured after a 12-hour fast. According to the 1997 American Diabetes Association (ADA), a normal fasting glucose measurement ranges between 70.2 to 100 milligrams per deciliter (mg/dL). A level between 100 and 126 mg/dL is considered pre-diabetic. A level of 126 mg/dL or above is diabetic.
By the 1997 standard, the researchers found that pre-diabetics in the studies with a fasting glucose measurement of 110 to 125 mg/dL carried a 21 percent higher chance of suffering a future stroke. Heart disease and stroke account for roughly two-thirds of all deaths among people with diabetes.
In 2003, however, the ADA redefined the fasting glucose level for pre-diabetes to 100 to 125 mg/dL. Using this less stringent definition, the researchers found no increased stroke risk for pre-diabetics. Indeed, when they analyzed three studies that provided information on participants with fasting glucose levels of 100 to 109 mg/dL they found no increased risk of stroke.
Ovbiagele said the difference in the findings suggests there may be a "threshold effect" in the relationship between fasting glucose levels and future stroke risk. "Elevated risk may only begin at or above a fasting glucose level of 110 mg/dL," he said.
Additional research is needed to determine the best definition predicting stroke risk among diabetics, Ovbiagele noted. It should include an assessment of more recent glycemic biomarkers, such as glycosylated hemoglobin, and be followed by randomized, controlled trials involving drugs and/or lifestyle modification to evaluate the effect of treatments on reducing the risk of future strokes.
"In the meantime, to avoid progression to diabetes or occurrence of strokes, clinicians should strongly consider recommending therapeutic lifestyle changes and maximizing the control of established stroke risk factors in their patients with pre-diabetes," Ovbiagele said.
Co-authors of the study are Meng Lee, Chang Gung University College of Medicine, Chiayi, Taiwan; Jeffrey L. Saver and Sarah Song, University of California, Los Angeles; Heun-Sik Hong, Inje University, South Korea and Kuo-Hsuan Chang, Chang Gung University College of Medicine, Linkuo, Taiwan.
Funding, in part, came from Chang Gung Memorial Hospital and the National Institutes of Health (grants P50 NS044378 and U01 NS079179).
Scott LaFee | EurekAlert!
'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers
16.02.2018 | National University of Science and Technology MISIS
New process allows tailor-made malaria research
16.02.2018 | Eberhard Karls Universität Tübingen
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Information Technology
19.02.2018 | Ecology, The Environment and Conservation
19.02.2018 | Life Sciences