Glycaemic measures and risk of mortality in older Chinese: the Guangzhou Biobank Cohort Study.

CONTEXT: China has the largest number of people with type 2 diabetes mellitus (T2DM) in the world. Data from previous studies suggested that up to one-fifth of individuals with diabetes would be missed without an oral glucose tolerance test (OGTT). To date there is little information on the mortality risk of these individuals.

OBJECTIVE: We estimated the association of different indicators of hyperglycaemia with mortality in the general Chinese population.

DESIGN: Prospective cohort study.

SETTING: China.

PARTICIPANTS: 17,939 participants aged 50+ years.

EXPOSURES: Previously diagnosed diabetes and newly detected diabetes defined by fasting glucose (≥7.0 mmol/L), 2h post-load glucose (≥11.1 mmol/L), or haemoglobin A1c (HbA1c, ≥6.5%).

MAIN OUTCOMES MEASURES: Deaths from all-cause, cardiovascular disease and cancer were identified by record linkage with death registration.

RESULTS: During 7.8 (standard deviation=1.5) years' follow-up, 1,439 deaths were recorded. Of 3,706 participants with T2DM, 2126 (57%) had known T2DM, 118 (3%) were identified by isolated elevated fasting glucose, 1022 (28%) had isolated elevated post-load glucose, and 440 (12%) had both elevated fasting and post-load glucose. Compared to normoglycaemia, the HR (95% CI) of all-cause mortality was 1.71 (1.46, 2.00), 0.96 (0.47, 1.93), 1.43 (1.15-1.78) and 1.82 (1.35-2.45) for the four groups above, respectively. T2DM defined by elevated HbA1c was not significantly associated with all-cause mortality (HR 1.17, 95% 0.81-1.69).

CONCLUSION: Individuals with isolated higher 2h post-load glucose had a higher risk of mortality by 43% than those with normoglycaemia. Under-use of OGTT leads to substantial under-detection of individuals with a higher mortality risk and lost opportunities for early intervention.