Prediabetes is the precursor stage before diabetes mellitus occurs. Not all of the symptoms required to diagnose diabetes are present but blood sugar is high. It includes people with impaired glucose tolerance and fasting glucose.
There has been much debate around the correct cut off point for the diagnosis of impaired fasting glucose, with different views emerging from major health organisations including the World Health Organisation (WHO) and the American Diabetes Association (ADA) guideline.
WHO defines impaired plasma glucose as fasting plasma glucose of 6.1 – 6.9 mmol/L whereas the ADA guideline recommended a cutoff point of 5.6-6.9 mmol/L. Some researchers believe that the differing cutoff points could be detrimental, in that the latter definition could greatly increase the prevalence of what is considered impaired fasting glucose, without any association with clinical complications such as heart disease and death rates.
Researchers decided to address the inconsistencies, evaluating associations between different definitions of prediabetes and the risk of heart events, coronary heart disease (CHD), stroke and all cause mortality.
Researchers conducted a meta-analysis of studies in the area, including prospective cohort studies involving baseline measures of blood glucose and other cardiovascular risk factors. All participants were aged 18 years or over.
Prediabetes in the analysis defines as impaired fasting glucose, including both the WHO definition (6.1-6.9mmol/L) and the ADA definition (5.6-6.9mmol/L), impaired glucose tolerance or raised HbA1c according to ADA criteria.
Primary outcomes assessed were risk of heart events and all cause death, and secondary outcomes were risk of CHD and stroke in people according to different definitions of prediabetes compared to people with normal blood sugar levels.
Researchers found that prediabetes, defined as impaired fasting glucose or impaired glucose tolerance, was associated with an increased risk of composite heart events, CHD, stroke and all cause death. They found this risk to be pronounced when fasting plasma glucose was at 5.6mmol/L as per the ADA definition of impaired fasting glucose.
The results of this study can help inform those at high risk of adverse heart events and encourage timely treatment and appropriate lifestyle modifications in people with prediabetic risk factors.