Prediabetes raises risk of heart disease and death

Article written by Bruce Sylvester

Among patients with a history of heart problems, prediabetes increases risks of heart disease and death, researchers reported on July 15, 2020 in the BMJ/British Medical Journal.

Prediabetes is a “pre-diagnosis” of diabetes, when the blood sugar level is elevated above normal, but not high enough to be called diabetes.

Investigators from the Southern Medical University in Guangzhou, China conducted a meta-analysis of data from a large group of relevant studies, “to evaluate the associations between prediabetes and the risk of all-cause mortality and incident cardiovascular disease in the general population and in patients with a history of atherosclerotic cardiovascular disease.”

In order to identify potentially eligible studies, they used the electronic databases PubMed, Embase, and Google Scholar up to 25 April 2020. They identified 129 studies to be included in the meta-analysis.

They defined “prediabetes” and “normoglycaemia” (normal blood glucose) according to criteria of the American Diabetes Association and the World Health organization. The World health Organization has estimated that more than 470 million people worldwide will have prediabetes by 2030 and as many as to 70% will  develop type 2 diabetes.

Eligible studies were either prospective studies or post hoc analyses of clinical trials.

The primary outcomes of the new meta-analysis were all cause mortality and composite cardiovascular disease. Secondary outcomes were the risk of coronary heart disease and stroke.

There were a total of 10,069,955 subjects in all of the trials. Findings in each study were adjusted for factors, such as age, sex, ethnicity, and lifestyle.

In their new analysis the investigators found that, in the general population and over an average follow-up time of around 10 years, prediabetes was associated with a 13% increased risk of all-cause mortality and a 15% increased risk of cardiovascular disease. Prediabetes was also linked a higher risk of coronary heart disease and stroke.

In absolute terms, this means that, among the study subjects with prediabetes, there were 7 extra deaths per 10,000 person years and almost 9 extra cases of cardiovascular disease per 10,000 person years in the general population, compared with normal blood sugar levels.

In those subjects with a history of heart disease and over an average of 3-year follow-up, prediabetes was associated with a 36% increased risk of all cause mortality and a 37% increased risk of cardiovascular disease. There was no increase in the risk of stroke.

In absolute terms, this equates to 66 extra deaths per 10,000 person years and almost 190 extra cases of cardiovascular disease per 10,000 person years, compared with normal blood sugar levels.

The researchers reported that impaired glucose tolerance (elevated blood sugar level after eating) carried a higher risk of all cause mortality, coronary heart disease and stroke than impaired fasting glucose (elevated blood sugar level after fasting).

The authors concluded, “Results indicated that prediabetes was associated with an increased risk of all cause mortality and cardiovascular disease in the general population and in patients with atherosclerotic cardiovascular disease. Screening and appropriate management of prediabetes might contribute to primary and secondary prevention of cardiovascular disease.”