The log-linearity of the effect of blood glucose was studied for all patients and for diabetic and nondiabetic patients separately. The effect was found to be not log-linear for both groups with an inflection of the smoothing splines at 7 mmol/l (126 mg/dl) for nondiabetic patients and at 10 mmol/l (180 mg/dl) for diabetic patients (6). Thus, hyperglycemia was defined as a glucose level of ≥7 mmol/l for nondiabetic subjects and ≥10 mmol/l for those with previous DM. Because patients from various countries were included, a potential cluster effect was taken into account using a generalized linear model with random intercept where the cluster of interest was the country. The effect of hyperglycemia on all-cause 30-day mortality was studied without and with adjustment for potential confounding factors. The confounders included in the multiple model were age, sex, comorbidities (history of chronic HF, history of coronary artery disease [CAD], diabetes mellitus), systolic blood pressure (SBP) or diastolic blood pressure, heart rate, impaired renal function (eGFR <60 ml/min/1.73 m2) (24) and sodium <136 mmol/l. Moreover, the effect of hyperglycemia on all-cause 30-day mortality was studied in various pairs of subgroups (including diabetic, nondiabetic, no anemia, anemia, de novo HF, decompensation of chronic HF, no history of CAD, history of CAD, ≤age 80 years, >80 years, no history of hypertension, history of hypertension, eGFR ≥60 ml/min/1.73 m2, eGFR <60 ml/min/1.73 m2, male, female, left ventricular ejection fraction [LVEF] ≥40%, LVEF <40%, LVEF ≥50%, LVEF <50%, median or lower B-type natriuretic peptide, B-type natriuretic peptide greater than median, SBP ≤140 mm Hg, and SBP >140 mm Hg). For each pair of subgroups, an interaction test was performed, indicating whether the difference of effect between the 2 subgroups was significant.