The results of the largest study thus far on mortality in adult-onset autoimmune diabetes were published online October 15 in Diabetes Care by Lisa Olsson, PhD, from the unit of epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockhom, Sweden, and colleagues.

Dr. Olsson told Medscape Medical News that the findings were a surprise, since those with autoimmune diabetes developed in adulthood clearly have a more favorable metabolic profile at baseline compared with individuals with type 2 diabetes, so ”one could have expected a lower mortality.”

Yet they found differently in their trial, one of the first to examine mortality in this type of adult-onset autoimmune diabetes, she noted. And they discovered that glycemic control is key — the excess mortality seen in this patient population, compared with the nondiabetic participants, was clearly associated with HbA_1c.

”It says something about the treatment in these patients… There was a clear association with poor glycemic control. The excess risk was also seen independently of traditional risk factors.”

Less Metabolic Syndrome, yet Equal Mortality to Type 2 Diabetes

Dr. Olsson and colleagues explain that adult-onset autoimmune diabetes (often termed latent autoimmune diabetes in adults [LADA]), which is estimated to account for 10% of all diabetes, differs slightly from ”classic” type 1 diabetes, which generally develops in childhood, in that it progresses more slowly and typically is not treated with insulin at the time of diagnosis.

They examined data from surveys in a large, prospective population-based Norwegian study conducted from 1995 to 2008 involving 208 adults who developed autoimmune diabetes (assessed by analysis for antiglutamic acid decarboxylase autoantibodies [GAD] antibodies) at age 35 years or older, 2425 with type 2 diabetes, and 61,631 without diabetes. For those without diabetes at baseline but who developed it during the study, the time since diagnosis was accounted for in the analysis.

Those who had or developed autoimmune diabetes in adulthood had less central obesity, lower triglycerides, and higher HDL cholesterol than those with type 2 diabetes. Metabolic syndrome was present in 55% of those with autoimmune diabetes, compared with 77% of those with type 2 diabetes. However, glycemic control was worse among those with autoimmune diabetes (HbA_1c 8.3% vs 7.7% in type 2 patients).

By linking the study population data with those of the Norwegian Cause of Death registry, the researchers found that 15% of those without diabetes died during the study period, compared with 33% of those with diabetes.

Hazard ratios for mortality among those with autoimmune diabetes compared with those without diabetes were 1.63 for all-cause mortality, 1.93 for cardiovascular disease (CVD) mortality, and 2.7 for ischemic heart disease (IHD) mortality. The type 2 diabetes group compared with those without diabetes had hazard ratios very similar to autoimmune-diabetes patients: 1.56, 1.90, and 2.62, respectively.

”Our findings indicate that mortality in autoimmune diabetes in adults is at least as high as in type 2 diabetes, including a more than twofold increased risk of death from IHD,” the authors write.

These results were similar after adjustment for a variety of relevant factors including age, sex, body mass index, smoking, alcohol consumption, education, family history of diabetes, metabolic syndrome, and each of the individual metabolic-syndrome components.

In both autoimmune and type 2 diabetes, excess mortality was greater among those with higher HbA_1c and fasting glucose levels. ”The excess risk was seen in men and women and was not explained by components of the metabolic syndrome or by socioeconomic factors but appeared for the major part to be associated with poor glycemic control,” Dr. Olsson and colleagues state.

Treating the Right Type of Diabetes

Adult-onset autoimmune diabetes hasn’t been widely studied, Dr. Olsson told Medscape Medical News.

”Even though about half of the cases of type 1 diabetes develop in adult life, there are few epidemiological studies in age groups above 30 to 40 years, most likely because there are few observational studies with the necessary data on autoimmune markers — eg, GAD antibodies — to separate autoimmune diabetes with adult onset from type 2 diabetes.”

Therefore, she said, ”We need to increase knowledge on risk factors for developing autoimmune diabetes in adults and on complications from this form of diabetes.”

She noted that testing for anti-GAD antibodies is not typically done in clinical practice and therefore some patients are probably misdiagnosed as having type 2 diabetes.

”Because of the clear association with poor glycemic control seen in our study, it is important that these individuals get the correct diagnosis and optimal treatment,” she concluded.

The HUNT Study is a collaboration between the HUNT Research Centre (Faculty of Medicine, Norwegian University of Science and Technology), the Nord-Trøndelag County Council, the Central Norway Health Authority, and the Norwegian Institute of Public Health. GlaxoSmithKline Norway supported the study financially through the Norwegian University of Science and Technology. This work was supported by a grant from the Swedish Council for Working Life and Social Research. The authors reported no conflicts of interest.

From http://www2.smartbrief.com/

Abstract

Mortality in Adult-Onset Autoimmune Diabetes Is Associated With Poor Glycemic Control

Results from the HUNT Study