Prediabetes is associated with elevated risk of clinical outcomes even without progression to diabetes

Prediabetes (HbA_1c 39–47 mmol/mol [5.7–6.4%] or fasting glucose 5.6–6.9 mmol/l) is associated with elevated risks of microvascular and macrovascular complications. It is unknown to what extent these risks in prediabetes remain after accounting for progression to diabetes.

In 10,310 participants from the Atherosclerosis Risk in Communities (ARIC) Study (aged 46–70 years, ~55% women, ~20% Black adults) without diabetes at baseline (1990–1992), we used Cox regression to characterise age- and sex-adjusted associations of prediabetes with ~30 year incidence of complications (composite and separately), including atherosclerotic CVD (ASCVD), heart failure, chronic kidney disease (CKD) and all-cause mortality before and after accounting for intervening incidence of diabetes, modelled as a time-varying variable. We calculated the excess risk of complications in prediabetes remaining after accounting for progression to diabetes.

Of the 60% of adults with prediabetes at baseline, ~30% progressed to diabetes (median time to diabetes, 7 years). Over the maximum follow-up of ~30 years, there were 7069 events (1937 ASCVD, 2109 heart failure, 3288 CKD and 4785 deaths). Prediabetes was modestly associated with risk of any complication (HR 1.21 [95% CI 1.15, 1.27]) vs normoglycaemia. This association remained significant after accounting for progression to diabetes (HR 1.18 [95% CI 1.12, 1.24]) with 85% (95% CI 75, 94%) of the excess risk of any complication in prediabetes remaining. Results were similar for the individual complications.

Progression to diabetes explained less than one-quarter of the risks of clinical outcomes associated with prediabetes. Prediabetes contributes to the risk of clinical outcomes even without progression to diabetes.