Poor blood sugar control increases the risk of heart failure in patients with type 1 diabetes, new research shows.
A study presented at the American Diabetes Association conference in San Diego this week found a four-fold increase in the risk of heart failure in patients with a HbA1c level of 10.5%, compared with those with levels below 6.5%.
Swedish researchers identified all patients aged 18 and over with type 1 diabetes and no known heart failure who were registered in the national diabetes registry between January 1998 and December 2003.
Some 21,000 patients were followed up until hospital admission for heart failure, death, or the end of the follow-up period on 31 December 2009. The study found 3% were admitted to hospital with a primary or secondary diagnosis of heart failure during a median follow-up of nine years, with an incidence of 3.38 events per 1000 patient-years.
Incidence increased with HbA1c, with a range of 1.42–5.20 events per 1000 patient-years between patients with the lowest level – below 6.5% – and highest –10.5% or higher.
After adjustment for age, sex, duration of diabetes, cardiovascular risk factors, myocardial infarction and other comorbidities, the hazard ratio for development of heart failure was 3.98 in patients with HbA1c of 10.5% or higher compared with patients with HbA1c of less than 6.5%.
The risk of heart failure increased with age and duration of diabetes, smoking, high systolic blood pressure, and raised body-mass index.
In the 635 patients admitted to hospital with heart failure, HbA1c was associated with a 36% increased risk of heart failure per 1% rise in HbA1c in patients who had a primary diagnosis of heart failure, and a 26% per 1% rise in HbA1c in patients who had a secondary diagnosis of heart failure.
Increasing HDL concentration had a protective effect, and reduced the risk by 40% per 1 mmol/L, but there was no significant relationship detected with LDL cholesterol.
Dr Marcus Lind, a physician at the department of molecular and clinical medicine at the University of Gothenburg, concluded: ‘The positive association between HbA1c and risk of heart failure in fairly young patients with type 1 diabetes indicates a potential for prevention of heart failure with improved glycaemic control.'
‘Because treatment for heart failure improves survival and quality of life, clinicians should be observant of signs of heart failure in management of patients with type 1 diabetes, starting at an early stage. Echocardiography might be warranted, especially in the presence of poor glycaemic control, long duration of diabetes or an adverse risk factor profile.'