Association between glucose tolerance and mortality among Japanese community‐dwelling older adults aged over 75 years: 12‐year observation of the Tosa Longitudinal Aging Study

Aim Although the relationship between impaired glucose tolerance (IGT) and mortality has been investigated in diverse populations, few studies have focused on older populations. This study aimed to investigate the relationship between glucose tolerance and overall mortality among populations aged ≥75 years. Methods Data were obtained from the Tosa Longitudinal Aging Study, a community‐based cohort survey conducted in Kochi, Japan. According to the results of a 75‐g oral glucose tolerance test conducted in 2006, the participants were classified into four categories: normal glucose tolerance (NGT), impaired fasting glucose (IFG)/IGT, newly diagnosed diabetes mellitus (NDM), and known diabetes mellitus (KDM). The primary endpoint was overall mortality. Differences in overall mortality among the four categories were evaluated using the Cox proportional hazards model. Results During a median of 11.5 years of observation, 125 deaths of the 260 enrolled participants were recorded. The cumulative overall survival rate was 0.52, and the survival rates of NGT, IFG/IGT, NDM, and KDM were 0.48, 0.49, 0.49, and 0.25, respectively (log‐rank test, P = 0.139). Adjusted hazard ratios (HRs) for mortality in the IFG/IGT and NDM groups compared with the NGT group were 1.02 (95% confidence interval [CI], 0.66–1.58) and 1.11 (95% CI, 0.56–2.22), while mortality in the KDM group was significantly higher than that in the NGT group (HR, 2.43; 95% CI, 1.35–4.37). Conclusion Mortality did not differ significantly between the IFG/IGT, NDM, and NGT groups, but was higher in the KDM group than in the NGT group. Geriatr Gerontol Int 2023; 23: 341–347 .