Prediabetes, Diabetes, and the Risk of All-Cause and Cause-Specific Mortality in a Japanese Working Population: Japan Epidemiology Collaboration on Occupational Health Study

Objective: Prediabetes has been suggested to increase mortality risk; however, the definitions of prediabetes that can predict mortality remain elusive. We prospectively investigated the association of multiple definitions of prediabetes with the risk of mortality from all-causes, cardiovascular disease (CVD), and cancer in Japanese workers.

Research design and methods: The study included 62,785 workers who underwent a health checkup in 2010 or 2011 and were followed up for mortality from 2012 to March 2019. Prediabetes was defined according to fasting plasma glucose (FPG) or glycated hemoglobin (HbA1c) level or a combination of both using the American Diabetes Association (ADA) or World Health Organization (WHO)/International Expert Committee (IEC) criteria. The Cox proportional hazards regression model was used to investigate the associations.

Results: Over a 7-year follow-up, 229 deaths were documented. Compared with normoglycemia, prediabetes defined according to ADA criteria was associated with a higher risk of all-cause (hazard ratio [HR] 1.53; 95% confidence interval [CI] 1.12–2.09) and cancer (HR 2.37; 95% CI 1.45–3.89) mortality but not with CVD mortality. The results were materially unchanged when prediabetes was defined according to ADA FPG, ADA HbA1c, WHO FPG, or combined WHO/IEC criteria. Diabetes was associated with the risk of all-cause, CVD, and cancer mortality.

Conclusion: In a cohort of Japanese workers, FPG- and HbA1c-defined prediabetes according to ADA or WHO/IEC was each associated with a significantly increased risk of mortality from all-causes and cancer but not CVD.