“This study shows that we need to identify better treatments for this large group of lean African patients,” says project leader Charles Agyemang of Amsterdam UMC.
Type 2 diabetes is commonly associated with overweight. In high-income countries, this picture is largely accurate: nine out of ten people with type 2 diabetes are overweight. In Africa, however, the situation is different. Almost four in ten African adults with type 2 diabetes are lean, with a normal or even low body weight. In rural areas in countries such as Ghana, this figure rises to six in ten.
“This means that there are an estimated ten million lean patients on the African continent who do not fit the standard profile,” says first author Sabrina Esmail of Amsterdam UMC. “For them, the problem is a lack of insulin rather than a reduced response to insulin.”
A different disease process requires a different treatment
Despite these differences, both groups in Africa almost always receive the same treatment, based on international guidelines: oral medication such as metformin or sulfonylureas. These medicines are primarily used to treat insulin resistance rather than insulin deficiency. Lean patients are therefore likely to receive treatment that does not match their form of the disease.
The researchers analysed data from more than 3,300 African adults with type 2 diabetes from Ghana, Nigeria, Kenya and Europe.
“Lean patients are more likely to develop eye damage, known as retinopathy, and to experience strokes,” says senior author Felix Chilunga. “People with overweight, by contrast, are more likely to have high blood pressure and an increased risk of cardiovascular disease. Chronic kidney disease occurred equally often in both groups.”
The amount of body fat explained most of these differences, pointing to genuinely distinct disease processes. The risk factors also differ. While overweight is often associated with an unhealthy lifestyle, lean patients are more likely to have experienced undernutrition or a low birth weight, which may affect the development of the pancreas.
Type 2 diabetes in lean Africans is therefore biologically and clinically a different subtype from the disease seen in people with overweight. Yet it is currently treated as if it were the same condition, potentially leaving millions of people without the care best suited to their needs.
“We are calling for targeted clinical studies to determine which treatments work best for this large and often overlooked group of patients,” says Chilunga.
People of African ancestry in Europe
People of African ancestry living in Europe are also likely to require a different approach to treatment. Previous research using UK Biobank data showed that people of African ancestry with a BMI of 26 have the same risk of diabetes as Europeans with a BMI of 30.
Studies among migrants in Europe have repeatedly shown that people of African ancestry are more likely to develop type 2 diabetes, develop it around ten years earlier and have poorer blood sugar control than the European-born population.
“A substantial proportion of African patients in Europe are lean, are treated according to guidelines developed for the form of the disease associated with overweight, and demonstrably have poorer diabetes control,” says Agyemang. “There is no reason to assume that the treatment mismatch we describe stops at the border.”
The study was conducted by Amsterdam UMC, the University of Ghana and the National Institutes of Health’s Center for Research on Genomics and Global Health, using data from the AADM and RODAM cohorts. RODAM is one of the cohorts connected to Amsterdam Cohort Hub.
Read the full study, published in Diabetologia: Divergent complication patterns of type 2 diabetes in African individuals who are lean versus overweight or obese: a multi-cohort analysis.