Are there actually multiple types of diabetes?


Diabetes has long been thought to consist of two main groups: type 1, which mostly affects younger people who are unable to produce insulin, and type 2, resulting in resistance to insulin, with glucose unable to enter cells even when there is sufficient insulin. 

According to a study published in The Lancet: Diabetes & Endocrinology, type 2 diabetes is divided into four distinct subtypes.

Although not discussed in the study, mention should also be made of gestational diabetes. Less common than types 1 and 2, it is a condition that may occur during pregnancy. Changing hormones and weight gain make it hard for the bodies of mothers-to-be body to keep up with their need for insulin. 

Different clusters

The groupings are referred to as clusters in the study:

Cluster 1 (Type 1 diabetes): These individuals are usually diagnosed before the age of 40. Peak age of diagnosis is around 14. Some type 1 diabetics are unable to make insulin because of an autoimmune disease.

Cluster 2 (Type 2 diabetes): This group is similar to cluster 1 as both include individuals with extreme insulin-deficient diabetes; however in their case their immune system is not involved. The condition is a result of poor metabolic control, indicated by high A1C levels, which is the two to three month average of blood sugar levels. Vision loss due to diabetes was more common in this group than any of the others.

Cluster 3 (Type 2 diabetes): These people are overweight, and while they do make insulin, their bodies do not respond to it. These individuals are considered highly resistant to insulin. This group also has a much higher risk of diabetic nephropathy.

Cluster 4 (Type 2 diabetes): The individuals in this cluster have mild obesity-related diabetes, but metabolically they are healthier than cluster three.

Cluster 5 (Type 2 diabetes): This cluster contains people who were older when they were diagnosed. Their diabetes was also the mildest and progressed the slowest.                                                                                                         

Effective treatment

These distinctions and groupings could help create more individualised and subsequently more effective care for diabetes patients. Senior study author, Dr Leif Groop, director of Lund University Diabetes Center in Sweden, explained in a press release by the journal, “Today, we intensify treatment after things have happened. With this new classification, it makes it possible to do it before things happen.”

Three-and-a-half million South Africans (about 6% of the population) suffer from diabetes and there are many more who are undiagnosed. According to a previous Health24 article, it is estimated that another five million South Africans have prediabetes, a condition where insulin resistance causes blood glucose levels to be higher than normal, but not high enough to be diagnosed as type 2 diabetes. 

Treatment would also be more effective if diagnoses were based on the specific characteristics of each patient’s age of diagnosis as well as their risks for kidney disease and loss of vision, both complications of diabetes.

Changing the way we think about diabetes

The researchers say that their grouping system could be helpful for both newly diagnosed diabetes patients as well as those who have had type 2 for many years. However, it has not been made clear whether patients can move between clusters as their condition changes. They go on to state that a larger study needs to be done that will include a larger variable and more diverse populations.

The study argues that it is more useful combining several different components to create more specific diabetes diagnoses than just using one based on glucose levels to diagnose either type 1 or type 2.

"This new substratification could change the way we think about type 2 diabetes and help to tailor and target early treatment to patients who would benefit most, thereby representing a first step towards precision medicine in diabetes," they maintain.

The potential impact of these clusters 

There have been criticisms of this study by doctors from all over the world. On of these critics is Dr Rob Sladek, a professor at McGill University and Genome Quebec Innovation Centre in Canada. 

Dr Sladek told Medscape Medical News that he "was not completely surprised" that there were as many as five clusters of diabetes.

"We already know that there is a group of adult-onset patients that are severely insulin deficient. In addition, we think of diabetes as being a balance between insulin needs or insulin resistance, say from obesity, and insulin production," he said.

Dr Groop admits that this might be an implementation problem, "The risk of missing important outcomes is clearly less than with the traditional classification." This is because lumping a very diverse group together makes it difficult to pinpoint differentiating risks. 

Despite the potential benefits of these groupings, diabetes experts have expressed their concerns and doubts and whether in reality, doctors would be able to apply them to their patients' care.

Image credit: iStock 

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