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Prediabetes linked with increased cardiovascular risk, even at lowest thresholds

By Jane Lewis
Prediabetes is associated with an increased risk of cardiovascular events, coronary heart disease (CHD), stroke and all-cause mortality, even when the lowest thresholds for prediabetes were used, reports a large meta-analysis in the BMJ.

Speaking to Endocrinology Today, Associate Professor Neale Cohen, endocrinologist and General Manager of Diabetes Services at Baker IDI, Melbourne, said prediabetes diagnosis was ‘a murky area’ and that the meta-analysis results were ‘reassuring’ in that they gave a clear message.

‘This research shows that no matter how you define it, prediabetes is linked with increased cardiovascular risk, as well as the risk of diabetes,’ he said.

The cut-off point for diagnosis of impaired fasting glucose is inconsistent among different guidelines and remains controversial, say the authors, who set out to evaluate associations between different definitions of prediabetes and the risk of cardiovascular disease and all-cause mortality.

To do so, they analysed the results of 53 prospective cohort studies, with a total of 1,611,339 participants and a median follow up of 9.5 years. Relative risks were found to vary according to the prediabetes definition used: impaired fasting glucose according to American Diabetes Association criteria (IFG-ADA), impaired fasting glucose according to World Health Organization criteria (IFG-WHO, which are the guidelines used in Australia), or impaired glucose tolerance (IGT).

Compared with normoglycaemia, prediabetes was associated with an increased risk of composite cardiovascular disease (relative risks [RRs], 1.13, 1.26 and 1.30 for IFG-ADA, IFG-WHO and IGT, respectively), CHD (RRs, 1.10, 1.18 and 1.20, respectively), stroke (RRs, 1.06, 1.17 and 1.20, respectively), and all-cause mortality (RRs, 1.13, 1.13 and 1.32, respectively).

The authors observed that the risks were increased even when the fasting plasma glucose level was as low as 5.6 mmol/L – the current ADA definition of impaired fasting glucose. They also observed that the risks for composite cardiovascular events and CHD were higher in people with prediabetes defined as raised HbA1c (≥ 39 mmol/mol).

‘These results support the lower cutoff point for impaired fasting glucose according to ADA criteria as well as the incorporation of HbA1c in defining prediabetes,’ they concluded.

‘In Australia, a significant proportion of our population – perhaps as high as 25% – has prediabetes,’ commented Associate Professor Cohen. ‘What do we do about that? That’s the really important question we need to answer.’
BMJ 2016; 355: i5953.