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Background: This study aimed to examine associations between haemoglobin A1c (HbA1c) levels over time and all-cause and cause-specific mortality in middle-aged and older Koreans. Methods: Using 16 years of follow-up data from the Korean Genome and Epidemiology Study, we analysed 9294 individuals aged 40–69 years with no history of cardiovascular disease (CVD) or cancer. Participants were divided into a known diabetes group and five groups categorized by HbA1c levels (< 5.0%, 5.0–5.4%, 5.5–5.9%, 6.0–6.4%, and ≥ 6.5%). Hazard ratios (HRs) for all-cause and cause-specific mortality associated with HbA1c levels were calculated using a conventional and a time-dependent Cox proportional hazards model. Restricted cubic spline models were fitted to investigate the relationship between continuous HbA1c levels and mortality among people without known diabetes. Subgroup analyses were performed for age, sex, smoking, hypertension, liver diseases, and red blood cell counts. Results: During a median follow-up period of 15.7 years, there were 944 deaths, including 185 deaths from CVD, 359 from cancer, and 125 from all external causes. Compared with participants with HbA1c levels of 5.5–5.9%, multivariate-adjusted HRs and 95% confidence intervals for all-cause death of participants with levels < 5.0%, 5.0–5.4%, 6.0–6.4%, and ≥ 6.5% and participants with known diabetes were 1.84 (1.35–2.51), 1.13 (0.95–1.34), 1.30 (1.04–1.62), 1.37 (0.97–1.93), and 2.03 (1.70–2.44), respectively. The risk of cancer mortality was significantly increased in HbA1c < 5.0% (HR, 2.21; 95% CI 1.42–3.44) and known diabetes (HR, 1.60; 95% CI 1.18–2.15). When we performed diverse subgroup analyses, low HbA1c levels at baseline were strongly associated with mortality in participants with liver diseases. Conclusions: We found U-shaped associations between HbA1c levels at baseline and over time and all-cause mortality in middle-aged and older Koreans. Additionally, the risk of cancer mortality increased both in low and high HbA1c groups, but CVD mortality increased only in high HbA1c group. In particular, people with liver diseases and low HbA1c levels had a high risk of all-cause mortality. Therefore, more careful management of these groups is suggested to identify any deteriorating health conditions. [ABSTRACT FROM AUTHOR]

Objectives To assess the relationship between hemoglobin concentration and cause-specific mortality. Design Cohort study. Setting Data from the government-sponsored Annual Geriatric Health Examination Program. Participants Community-dwelling Taipei citizens aged 65 and older followed up between 2006 and 2010 (N = 77,532). Measurements Mortality was determined by matching participants' medical records with national death files. Cox proportional hazards regression models were used to evaluate the relationship between hemoglobin concentration (World Health Organization ( WHO)-defined anemia and 7 hemoglobin concentrations) and cause-specific mortality. Results The mortality risk of WHO-defined anemia increased substantially in both sexes for all-cause and cancer mortalities (men, hazard ratio ( HR) = 1.86, 95% confidence interval ( CI) = 1.71-2.02 for all-cause mortality; HR = 1.94, 95% CI = 1.69-2.22 for cancer mortality; for women, HR = 1.63, 95% CI = 1.43-1.86 for all-cause mortality; HR = 1.74, 95% CI = 1.38-2.19 for cancer mortality). Men with hemoglobin concentrations of 15.0 to 15.9 g/ dL and women with hemoglobin concentrations of 13.0 to 13.9 g/ dL had the lowest risks of all-cause, cardiovascular, and cancer mortality. Risks of all-cause and cancer mortality increased significantly when hemoglobin concentrations were less than 14 g/ dL in men and less than 12 g/ dL in women. Even mild anemia (11.0-11.9 g/ dL) was associated with greater mortality risk. Stratification according to age, body mass index, estimated glomerular filtration rate, and presence of comorbidities did not lead to any substantial changes. Conclusion Hemoglobin concentrations associated with optimal survival in older adults were identified and additional data provided regarding the relationship between hemoglobin concentrations and cause-specific mortality risks in older adults. [ABSTRACT FROM AUTHOR]