Academic corner: Africa's lurking diabetes burden

"What HIV/AIDS was in the last 20 years of the 20th century, diabetes and its consequences

will be in the first 20 years of this century." (Professor Paul Zimmet)

Diabetes and other non-communicable diseases were once thought to be essentially conditions of Western affluence, but this has now proven to be a myth belonging to the past. As poorer nations advance economically and move from rural traditional life styles to urban communities, they are experiencing a rising prevalence of diabetes which can only be described as a pandemic.

The global number of individuals with diabetes in year 2000 was estimated to be 171 million corresponding to 2.8% of the world’s population. According to the WHO this figure is projected to increase to 366 million by 2030 of whom 298 million (81%) will live in developing countries.  Estimates specifically for sub-Saharan Africa are disturbing – not in terms of actual numbers but in terms of an increase from 7 million people with diabetes in 2000 to an expected 19 million in 2030. This is particularly alarming because health care systems in Africa’s low income countries are badly prepared for the lurking burden of diabetes.

Urban growth and longer life

Why is it that malnourished, poor countries get affected by a disease pattern traditionally reserved for richer nations with well or over nourished populations? The answer is to be found in the rapid increase in population and increased longevity, coupled with rapid urbanisation and changes from traditional lifestyles accompanying increased economic activity and development.

Despite relatively low levels of urbanisation, developing countries now have more than twice as many urban dwellers as developed regions (2.3 billion compared to 0.9 billion). Between 2000 and 2030, Africa’s urban population will increase from 294 million to 742 million, and by 2030 80% of the world’s urban population will live in developing countries. Along with urbanisation, people also live longer. Life expectancy at birth in Africa has risen from 52 years in 1990 to 55 years in 2010, in spite of temporary set-backs due to HIV/AIDS. Twenty years later, in 2030 a person is expected to live 61 years.  

Now what makes an urban body with a longer life expectancy develop diabetes? Socio-economic changes in the developing countries are playing a major role in the rising incidence of diabetes. All over the world, traditional lifestyles and dietary patterns that sustained people over generations are disappearing. The traditional nutritious diets are being replaced by poor quality western-style cooking that uses more processing, more fat, salt, sugar, oil and meat. Said in popular terms, the change from rural to urban life is a change from physically demanding ‘food production and processing to a more sedentary life with TV, cola and chips.

Surrender to the eternal feasting

Human metabolism programmed to a life style of hunter-gatherer (fasting and feasting) enabled us survive tough times in the past. But it is unable to cope with modern living conditions of too little physical activity and constant feasting on refined foods. The tissues that store energy, i.e. muscles, liver and fat depend on insulin to help them achieve this by facilitating the entry of glucose into the cells. When exposed to energy oversupply these tissues protect themselves from being flooded by the excess by developing insulin resistance i.e, the cells resist the action of insulin in an attempt to block glucose from entering the cells.

When this happens initially, insulin producing Beta-cells compensate by secreting more insulin resulting in a new balance with relative excess of insulin, excess nutrient stores, but with a normal blood sugar. Later, insulin secretion can no longer compensate, and glucose tolerance becomes impaired (IGT), often followed by type 2 diabetes. This typifies the classical overweight person with diabetes.

Programmed at birth

While overweight is one explanation for developing type 2 diabetes, only half of diabetes cases in Africa are attributable to obesity. What other factors might then explain the rise in diabetes in Africans who are far from overweight – or may not even have enough food?

Research suggests that the metabolic disorder later causing type 2 diabetes may already be programmed in the womb of a malnourished pregnant woman. A baby in the womb of a malnourished mother will be programmed to survive in a nutritionally deficient state. This low-birth weight baby is born insulin resistant. With improved living standard or urban migration the child is exposed to relative nutritional excess in adult life which adds to the insulin resistance. The small pancreas and consequent lower -cell mass do not allow compensation by more insulin secretion and even before gaining weight or becoming obese, he or she will develop diabetes. One might say that the child has survived in the womb, but at the expense of not being fit for modern, urban life.

These findings cause scientists to call for rethinking food aid programmes also: “The fact that diabetes can now be connected to under-nutrition is astonishing and should leave us to rethink how we distribute food in a situation of famine. First priority must be given to pregnant women, to protect themselves as well as their offspring. And when re-feeding starved children, care must be taken to do no harm by relative overfeeding by too rich food packages. It is tempting to make the child catch up growth as fast as possible - but their small bodies may not be able to tolerate it as well as we once thought. It is a paradox that both over- and under-nutrition may lead to type 2 diabetes, but we have to learn the lessons, and find a new balance. On the other hand, it is fascinating that prevention of type 2 diabetes may start even before birth! ” says Professor Ib Bygbjerg at the Department of International Public Health at the University of Copenhagen, Denmark.

The stress factor

Besides the nutritional changes described above, the stress of urban living or urban migration may unmask a genetic predisposition to -cell failure. Undue psychological, emotional or physical stress leads to liberation of an excess amount of stress hormones that oppose the effects of insulin. While stress adds to the above mechanisms, it may act on its own as well. These reasons are often cited to explain the high prevalence of diabetes amongst migrant Asians, and also the rising prevalence in urban areas of developing economies worldwide.

The same life style related risk factors are common for other non-communicable diseases such as coronary heart disease, high blood pressure, obesity etc, which are often present along with diabetes. Consequently, it makes sense to talk about non-communicable diseases as a whole as the causative factors are closely related and the efforts to face the pandemic are similar.

A discrepancy to be addressed

The rise in non-communicable diseases has not simply displaced infectious diseases in developing countries. Rather, it has left developing countries with a double burden of diseases. This double burden of chronic and infectious diseases is straining the health services and leading to growing economic costs. While many developed nations have already focused considerable efforts on addressing the burden of chronic diseases, the rising burden of chronic diseases on developing countries has received inadequate attention.

The currents of development aid do far from depict the reality of chronic diseases projected to cause 60% of deaths in developing countries by 2020. In 2002, overseas development aid to the health sector amounted to USD 2.2 billion. Most of this was directed towards HIV/AIDS, and only 0.1% for chronic diseases. This discrepancy will have to be addressed by the global community by focussing on preventive care. Until that happens, the number of people with diabetes worldwide will continue to grow

Health promotion and primary prevention both have the potential to prevent or delay the onset of type 2 diabetes and it has a salutary effect on the risk of the other common non-communicable diseases such as obesity, arterial hypertension, cancer, stroke and heart diseases. That is why raising awareness of diabetes and attempts to reduce the burden of the disease and its complications are increasingly important in projects funded by the World Diabetes Foundation now and in the future.