By Paul Taylor | Special To The Globe And Mail
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As you point out, diabetes has traditionally been divided into two types.
Type 1 is an autoimmune disease. This means the patient’s own immune system starts destroying insulin-producing cells in the pancreas. Insulin is a hormone that’s needed to move sugar from the bloodstream into the body’s tissues, where it’s used for energy. Eventually, people with type 1 diabetes need regular insulin injections to compensate for what they no longer produce themselves. Patients tend to develop the condition at a young age.
Type 2 is the most common form of diabetes accounting for 85 to 90 per cent of cases. It usually develops later in life and it’s often associated with being overweight. The pancreas can’t produce enough insulin to meet the needs of a larger body mass or the cells no longer respond properly to insulin – a condition known as insulin resistance. It’s often treated with medications to make the body more responsive to insulin or to boost insulin production.
With either type of diabetes, poorly controlled blood-sugar levels can lead to medical complications, including heart attack, stroke, kidney failure, blindness and limb amputation.
Doctors who specialize in treating diabetes have long known that not all their patients fit neatly into one of these two categories.
So, researchers in Sweden and Finland analyzed data from 14,775 patients in order to create a more fine-tuned picture of diabetes.
They came up with the following five clusters, or types, of diabetes
- Cluster 1 most closely resembles the traditional definition of type 1 – an autoimmune disease. Patients cease to produce insulin and a blood test will reveal the presence of immune cells called antibodies. These patients, who can develop the condition at any age, are at high risk of complications.
- Cluster 2 is similar to cluster 1, although there’s no evidence of antibodies attacking the pancreas. It’s possible that this is also an autoimmune disorder, but doctors haven’t yet identified the antibodies involved. These patients are at high risk of complications – notably, eye problems.
- Cluster 3 is associated with being overweight. The pancreas still makes insulin, but not enough or, the body doesn’t respond well to the insulin that is produced. These patients are at high risk of complications, especially kidney disease.
- Cluster 4 patients have similar characteristics to those in cluster 3. However, these patients are less likely to experience serious complications.
- Cluster 5 is primarily made up of people who develop diabetes after the age of 65. They tend to have a milder form of the disease with lower risk of some complications.
The study, published in The Lancet Diabetes & Endocrinology, also found evidence that different genes appear to be involved in each cluster. This genetic variation may partly explain the distinct characteristics of each cluster and why some patients face an elevated risk of certain complications, says Dr. Rob Sladek, an associate professor at McGill University in Montreal. The findings still need to be confirmed with additional research. The clusters are based solely on people from two Nordic countries and there might be considerable differences in other populations, says Dr. Sladek, who wrote a comment article that accompanied the study. Even so, the study represents a watershed moment for diabetes.
“It challenges the traditional classifications of diabetes in a meaningful way,” says Dr. Jeremy Gilbert, a staff endocrinologist at Sunnybrook Health Sciences Centre in Toronto. “This may lead to changes in how we manage diabetes and result in more individualized, patient-centred care,” adds Gilbert. In particular, a new way of categorizing patients could help doctors identify individuals who are most likely to develop complications and need extra attention. “Not all people with adult forms of diabetes are the same and they may benefit from getting specific therapies, says Sladek.
It’s possible that early intervention with targeted treatments could help prevent or postpone potentially life-threatening complications. But don’t expect change in your care tomorrow. The researchers used diagnostic tests that are not commonly available to doctors. And it will take some time before these findings affect how patients are treated.
