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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., (© 2023 Japan Geriatrics Society.)

Objectives: To clarify the association between glucose intolerance and high altitudes (2900-4800 m) in a hypoxic environment in Tibetan highlanders and to verify the hypothesis that high altitude dwelling increases vulnerability to diabetes mellitus (DM) accelerated by lifestyle change or ageing., Design: Cross-sectional epidemiological study on Tibetan highlanders., Participants: We enrolled 1258 participants aged 40-87 years. The rural population comprised farmers in Domkhar (altitude 2900-3800 m) and nomads in Haiyan (3000-3100 m), Ryuho (4400 m) and Changthang (4300-4800 m). Urban area participants were from Leh (3300 m) and Jiegu (3700 m)., Main Outcome Measure: Participants were classified into six glucose tolerance-based groups: DM, intermediate hyperglycaemia (IHG), normoglycaemia (NG), fasting DM, fasting IHG and fasting NG. Prevalence of glucose intolerance was compared in farmers, nomads and urban dwellers. Effects of dwelling at high altitude or hypoxia on glucose intolerance were analysed with the confounding factors of age, sex, obesity, lipids, haemoglobin, hypertension and lifestyle, using multiple logistic regression., Results: The prevalence of DM (fasting DM)/IHG (fasting IHG) was 8.9% (6.5%)/25.1% (12.7%), respectively, in all participants. This prevalence was higher in urban dwellers (9.5% (7.1%)/28.5% (11.7%)) and in farmers (8.5% (6.1%)/28.5% (18.3%)) compared with nomads (8.2% (5.7%)/15.7% (9.7%)) (p=0.0140/0.0001). Dwelling at high altitude was significantly associated with fasting IHG+fasting DM/fasting DM (ORs for >4500 and 3500-4499 m were 3.59/4.36 and 2.07/1.76 vs <3500 m, respectively). After adjusting for lifestyle change, hypoxaemia and polycythaemia were closely associated with glucose intolerance., Conclusions: Socioeconomic factors, hypoxaemia and the effects of altitudes >3500 m play a major role in the high prevalence of glucose intolerance in highlanders. Tibetan highlanders may be vulnerable to glucose intolerance, with polycythaemia as a sign of poor hypoxic adaptation, accelerated by lifestyle change and ageing., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)