The effect of glycaemic control and glycaemic variability on mortality in patients hospitalized with congestive heart failure

Background Diabetes and CHF are common comorbidities in hospitalized patients but the relationship between glycaemic control, glycaemic variability, and mortality in patients with both conditions is unclear. Methods We used administrative data to retrospectively identify patients with a diagnosis of CHF who underwent frequent glucose assessments. TWMG was compared with other measures of glycaemic control and a time-weighted measure of glycaemic variability, the glycaemic lability index. The outcome was hospital mortality. Results A total of 748 patients were included in the final analysis. Time-weighted mean glucose was higher than unadjusted mean glucose (137 +/- 44.7 mg/dL versus 167 +/- 54.9, p < 0.001), due in part to shorter sampling intervals at higher glucose levels. Hypoglycaemia, defined as a glucose level <70 mg/dL, occurred during 6.3% of patient-days in survivors and 8.4% of patient-days among nonsurvivors (p = 0.05). Time-weighted mean glucose was similar (128 +/- 33.1 mg/dL versus 138 +/- 45.1 mg/dL) in nonsurvivors versus survivors, p = 0.19). However, relatively few patients had were significantly elevated readings. Median GLI was higher in nonsurvivors compared with that in survivors (18.1 versus 6.82, p = 0.0003). Increasing glycaemic lability index (odds ratio 1.32, 95% confidence interval 1.05-1.65), and hypoglycaemia (odds ratio 2.21, 95% confidence interval 1.07-4.65), were independently associated with higher mortality in logistic regression analysis. Respiratory failure was associated with mortality, but not standard deviation of glucose. Conclusions Future studies analysing glycaemic control should control for variable sampling intervals. In this analysis, glycaemic lability index was independently associated with increased mortality, independent of hypoglycaemia. Prospective studies are needed to evaluate these findings. Copyright (C) 2010 John Wiley & Sons, Ltd.