Increased Diabetes Prevalence Due to Medical Advances

A new study has concluded that the global increase in type 1 diabetes (T1D) mellitus is directly linked to reduced natural selection resulting from improved medical care.

Researchers at the University of Adelaide (UA; Australia) and the University of Zurich (UZH; Switzerland) examined the prevalence of T1D in 118 countries and concurrent changes in life expectancy from 1950 to 2010 to test correlation of T1D to reduced natural selection, as measured by the Biological State Index. To do so, they first obtain country-specific estimates of T1D prevalence, life expectancy, obesity prevalence rate, urbanization rates, per capita sugars consumption, and per capita gross domestic product (GDP).

The data obtained were then matched to T1D prevalence in all the countries, which were also grouped to study associations in different geographical regions. After applying the Biological State Index to the data, they found that the rapid worldwide increase in T1D over the last few decades was directly linked with increases in human life expectancy, especially in Western countries, and therefore a reduction in natural selection. The study was published on March 2, 2106, in BMJ Open Diabetes Research & Care.

“The current prevailing paradigm on the increasing prevalence of T1D is that environmental pressures are now able to trigger genotypes. Currently, medical gene intervention in modern medicine at this stage cannot remove T1D genes, and eugenics can offer no direction due to ethics issue,” concluded study co-author Wen-Peng You, PhD, of UA. “Study of T1D epidemiology based on prevalence/incidence T1D data of all age groups has become imperative, as it may offer optimal solution to address, or at least slow down, T1D genetic load increases in different populations.”

“Natural selection is one of the major evolutionary forces that inform changes in our genes, across populations and over generations. This is the first major disease we have shown that is accumulating due to a relaxation of natural selection over time,” said study co-author Professor Maciej Henneberg, PhD, of UA and UZH. “It's unlikely this situation will ever be reversed, meaning that in order to overcome the problems associated with type 1 diabetes for our population, some form of gene therapy to repair the faulty genes may need to be considered.”

Natural selection, one of the basic mechanisms of evolution, is the differential survival and fertility of individuals due to differences in phenotype that reflect genetic differences. In modern society, natural selection still acts on all members of a population, selecting those that have an increased reproductive success due to survival and/or fertility. The Biological State Index takes into account potential loss of reproductive success by dying at an earlier age. The effect of natural selection on contemporary populations is declining due to modern medicine.

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University of Adelaide
University of Zurich