Articles
Novel subgroups of adult-onset diabetes and their association with outcomes: a data-driven cluster analysis of six variables

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Summary

Background

Diabetes is presently classified into two main forms, type 1 and type 2 diabetes, but type 2 diabetes in particular is highly heterogeneous. A refined classification could provide a powerful tool to individualise treatment regimens and identify individuals with increased risk of complications at diagnosis.

Methods

We did data-driven cluster analysis (k-means and hierarchical clustering) in patients with newly diagnosed diabetes (n=8980) from the Swedish All New Diabetics in Scania cohort. Clusters were based on six variables (glutamate decarboxylase antibodies, age at diagnosis, BMI, HbA1c, and homoeostatic model assessment 2 estimates of β-cell function and insulin resistance), and were related to prospective data from patient records on development of complications and prescription of medication. Replication was done in three independent cohorts: the Scania Diabetes Registry (n=1466), All New Diabetics in Uppsala (n=844), and Diabetes Registry Vaasa (n=3485). Cox regression and logistic regression were used to compare time to medication, time to reaching the treatment goal, and risk of diabetic complications and genetic associations.

Findings

We identified five replicable clusters of patients with diabetes, which had significantly different patient characteristics and risk of diabetic complications. In particular, individuals in cluster 3 (most resistant to insulin) had significantly higher risk of diabetic kidney disease than individuals in clusters 4 and 5, but had been prescribed similar diabetes treatment. Cluster 2 (insulin deficient) had the highest risk of retinopathy. In support of the clustering, genetic associations in the clusters differed from those seen in traditional type 2 diabetes.

Interpretation

We stratified patients into five subgroups with differing disease progression and risk of diabetic complications. This new substratification might eventually help to tailor and target early treatment to patients who would benefit most, thereby representing a first step towards precision medicine in diabetes.

Funding

Swedish Research Council, European Research Council, Vinnova, Academy of Finland, Novo Nordisk Foundation, Scania University Hospital, Sigrid Juselius Foundation, Innovative Medicines Initiative 2 Joint Undertaking, Vasa Hospital district, Jakobstadsnejden Heart Foundation, Folkhälsan Research Foundation, Ollqvist Foundation, and Swedish Foundation for Strategic Research.

Introduction

Diabetes is the fastest increasing disease worldwide and a substantial threat to human health.1 Existing treatment strategies have been unable to stop the progressive course of the disease and prevent development of chronic diabetic complications. One explanation for these shortcomings is that diagnosis of diabetes is based on measurement of only one metabolite, glucose, but the disease is heterogeneous with regard to clinical presentation and progression.

Diabetes classification into type 1 and type 2 diabetes relies primarily on the presence (type 1 diabetes) or absence (type 2 diabetes) of autoantibodies against pancreatic islet β-cell antigens and age at diagnosis (younger for type 1 diabetes). With this approach, 75–85% of patients are classified as having type 2 diabetes. A third subgroup, latent autoimmune diabetes in adults (LADA; affecting <10% of people with diabetes), defined by the presence of glutamic acid decarboxylase antibodies (GADA), is phenotypically indistinguishable from type 2 diabetes at diagnosis, but becomes increasingly similar to type 1 diabetes over time.2 With the introduction of gene sequencing in clinical diagnostics, several rare monogenic forms of diabetes were described, including maturity-onset diabetes of the young and neonatal diabetes.3, 4

Existing treatment guidelines are limited by the fact they respond to poor metabolic control when it has developed, but do not have means to predict which patients will need intensified treatment. Evidence suggests that early treatment is crucial for prevention of life-shortening complications because target tissues seem to remember poor metabolic control decades later (so-called metabolic memory).5, 6

A refined classification could provide a powerful tool to identify at diagnosis those at greatest risk of complications and enable individualised treatment regimens in the same way as genetic diagnosis of monogenic diabetes guides clinicians to optimal treatment.7 With this aim, we present a novel diabetes classification based on unsupervised, data-driven cluster analysis of six commonly measured variables and compare it metabolically, genetically, and clinically to the current classification in four separate populations from Sweden and Finland.

Research in context

Evidence before this study

National guidelines maintain information about diabetes classification, but this classification has not been much updated during the past 20 years, and very few attempts have been made to explore heterogeneity of type 2 diabetes. We searched PubMed up to Jan 1, 2017, using the Medical Subject Heading terms “diabetes mellitus”, “type 2”, and “classification”. We identified several calls from expert groups for a revised classification, but few efforts to subgroup type 2 diabetes, none of which have been implemented in the clinic.

Added value of this study

In this study, a data-driven cluster analysis of six simple variables measured at diagnosis in adult patients with newly diagnosed diabetes (n=14 755) identified five replicable clusters of patients with significantly different characteristics and risk of diabetic complications. These included a cluster of very insulin-resistant individuals with significantly higher risk of diabetic kidney disease than the other clusters, a cluster of relatively young insulin-deficient individuals with poor metabolic control (high HbA1c), and a large group of elderly patients with the most benign disease course.

Implications of all the available evidence

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.

Section snippets

Study populations

We used data from five cohorts: All New Diabetics in Scania (ANDIS), the Scania Diabetes Registry (SDR), All New Diabetics in Uppsala (ANDIU), Diabetes Registry Vaasa (DIREVA), and Malmö Diet and Cancer CardioVascular Arm (MDC-CVA).

The ANDIS project aims to recruit all incident cases of diabetes within Scania County in Sweden (about 1 200 000 inhabitants). All health-care providers in Scania were invited; the current registration covered the period from Jan 1, 2008, to Nov 3, 2016, during which

Results

We first analysed the ANDIS cohort, consisting of 14 652 patients with newly diagnosed diabetes from Sweden, 932 (6·4%) of whom were registered before age 18 years and were not included in our analysis of adult diabetes. Of the 13 720 adult patients, 204 (1·5%) had type 1 diabetes, 723 (5·3%) had LADA, 162 (1·2%) had secondary diabetes (coexisting pancreatic disease), and 519 (3·8%) were unclassifiable because of missing data. The remaining 12 112 (88·3%) patients were considered to have type 2

Discussion

Taken together, the results of our study suggest that this new clustering of patients with adult-onset diabetes is superior to the classic diabetes classification because it identifies patients at high risk of diabetic complications at diagnosis and provides information about underlying disease mechanisms, thereby guiding choice of therapy. By contrast with previous attempts to dissect the heterogeneity of diabetes,23 we used variables reflective of key aspects of diabetes that are monitored in

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