Diabetes is actually five separate diseases,” reports BBC News on a study looking at nearly 9,000 people with diabetes in Sweden and Finland.

The American Diabetes Association classifies diabetes into four major categories: type 1 diabetes (insulin deficient), type 2 diabetes, gestational diabetes (diabetes in pregnancy), and specific types of diabetes due to other causes, such as maturity-onset diabetes of the young (MODY), disease of exocrine pancreas, latent autoimmune diabetes in adults (LADA).

Recently, in a study published in The Lancet Diabetes and Endocrinology, Swedish researchers characterized five subgroups of diabetes, varying in severity from mild to severe. While the classification of type 1 diabetes remained unchanged, they grouped type 2 diabetes, into four distinct subgroups.They believe that classifying diabetes, using these subgroups helps to identify people with diabetes at most risk of developing complications. 
Cluster Name Description Number/Percentage
Cluster 1 Severe autoimmune disease (SAID) early-onset disease, relatively low body mass idex (BMI), poor metabolic control, insulin deficiency, and presence of GADA 577 (6.4%)
Cluster 2 Severe insulin-deficient diabetes (SIDD) No presence of GADA, relatively low BMI, low insulin secretion, low homoeostatic model assessment 2 of beta cell function (HOMA2-B), and poor metabolic control 1575 (17.5%)
Cluster 3 Severe insulin-resistant diabetes (SIRD) Insulin resistance, high HOMA2-IR index (homeostasis model assessment as an index of insulin resistance), and high BMI 1373 (15.3%)
Cluster 4 Mild obesity-related disease Presence of obesity, but no insulin resistance 1942 (21.6%)
Cluster 5 Mild age-related diabetes (MARD) Older patients than other clusters, similar description to cluster 4, but only modest metabolic derangements 3513 (39.1%)


The researchers compared disease progression, treatment, and development of diabetes-related complications between clusters. They found that people who were in cluster 1 and 2 had substantially higher hemoglobin A1c’s at diagnosis than other clusters. Ketoacidosis at diagnosis was more common in cluster 1, which makes sense, since this cluster presents with insulin deficiency and presence of GADA (two determinants of type 1 diabetes). Cluster 3 had the highest prevalence of nonalcoholic fatty liver disease.

They also found that those with more severe forms, such as those who were severely insulin resistant (cluster 3), had a significantly higher risk of developing diabetic kidney disease compared to other groups. Additionally, retinopathy (diabetes related eye disease) was higher in those who were severely insulin deficient (cluster 2). Cluster 5, older patients with type 2 diabetes, had the most benign disease course. 
However, this study alone is not sufficient to lead to changes in diabetes treatment guidelines, as it was only based on groups of diabetes patients in Scandinavia. The clusters and associated complications will need to be verified in other populations, including other ethnicities that may have a different risk of diabetes, such as Asian populations.