This study aimed to prospectively examine whether low normal glucose levels and hypoglycaemia are associated with increased mortality due to external causes, especially unintentional accidents.

A total of 345,318 normoglycaemic Korean adults who had undergone health examinations during 2002–2003 were followed-up to 2013. To avoid potential biases related to glucose-lowering medication use, those with known diabetes or hyperglycaemia were excluded.

During 3.6 million person-years of follow-up, 1293 participants died because of unintentional accidents. Hazard ratios (HRs) for these accidental deaths were 1.26 (95% CI: 1.11–1.42), 1.60 (1.21–2.11) and 3.07 (1.37–6.85) for fasting serum glucose (FSG) levels of 70–79, 55–69 and <55mg/dL (3.9–4.4, 3.05–3.83 and <3.05mmol/L), respectively, compared with 80–99mg/dL (4.44–5.5mmol/L). FSG levels<80mg/dL were associated with an approximately 30% higher mortality due to accidents: specifically, 40% were non-fall-related injury; 50% were automobile-related; and 80% were motorcycle-related. The associations were weak (approximately 10% higher mortality, with P>0.05 for each cause) for deaths due to traffic accidents (pedestrians, pedal cyclists), falls, intentional self-harm and physical assault. The population attributable risks for FSG levels <80mg/dL were 10% (95% CI: 2–18%) for non-fall-related injury, 11% (6–17%) for car accidents and 17% (6–27%) for motorcycle accidents.

FSG levels of 70–79mg/dL (3.9–4.4mmol/L) as well as <70mg/dL are risk factors for accidental death. Appropriate management of the impact of FSG levels <80mg/dL might reduce unintended deaths due to non-fall-related injury, and automobile and motorcycle accidents, by ≥10%.