Achieved levels of HbA1c and likelihood of hospital admission in people with type 1 diabetes in the Scottish population: a study from the Scottish Diabetes Research Network Epidemiology Group

OBJECTIVE-People with type 1 diabetes have increased risk of hospital admission compared with those without diabetes. We hypothesized that HbA(1c) would be an important indicator of risk of hospital admission.

RESEARCH DESIGN AND METHODS-The Scottish Care Information Diabetes Collaboration, a dynamic national register of diagnosed cases of diabetes in Scotland, was linked to national data on admissions. We identified 24,750 people with type 1 diabetes during January 2005 to December 2007. We assessed the relationship between deciles of mean HbA(1c) and hospital admissions in people with type 1 diabetes adjusting for patient characteristics.

RESULTS-There were 3,229 hospital admissions. Of the admissions, 8.1% of people had mean HbA(1c) <7.0% (53 mmol/mol) and 16.3% had HbA(1c) <7.5% (58 mmol/mol). The lowest odds of admission were associated with HbA(1c) 7.7-8.7% (61-72 mmol/mol). When compared with this decile, a J-shaped relationship existed between HbA(1c) and admission. The highest HbA(1c) decile (10.8-18.4%/95-178 mmol/mol) showed significantly higher odds ratio (95% CI) for any admission (2.80, 2.51-3.12); the lowest HbA(1c) decile (4.4-7.1%/25-54 mmol/mol) showed an increase in odds of admission of 1.29 (1.10-1.51). The highest HbA(1c) decile experienced significantly higher odds of diabetes-related (3.31, 2.94-3.72) and diabetes ketoacidosis admissions (10.18, 7.96-13.01).

CONCLUSIONS-People with type 1 diabetes with highest and lowest mean HbA(1c) values were associated with increased odds of admission. People with high HbA(1c) (>10.8%/95 mmol/mol) were at particularly high risk. There is the need to develop effective interventions to reduce this risk.