The developing world is being infested by Western-style social health problems such as obesity and "couch-potato" living, which could ultimately widen the global gap between rich and poor, new research suggests.

The study, carried out at Cambridge University, argues that the gradual Westernisation of the developing world is causing a surge in conditions such as heart disease, cancer, respiratory disease and diabetes, costing tens of millions of lives.

Such is the mortality rate from these chronic diseases that they could slow down economic growth by killing off large numbers of people of working age.

The report, published in The Milbank Quarterly, calls on governments and global health organisations to channel more of their efforts into fighting these conditions not just to save lives, but to prevent crippling economic slowdown in some of the world's poorest nations.

"The neglect of chronic diseases could have devastating economic consequences in developing countries which could in turn ensure that death rates from these conditions remained high," David Stuckler, a social epidemiologist at Cambridge University, who carried out the study, said.

"If no action is taken, there is a very real danger that this will widen not only the global health gap between rich and poor, but the wealth gap as well."

Although persistent challenges remain, succeeding decades of international health initiatives have helped to drive down infectious diseases such as malaria in the developing world.

In the meantime, however, chronic diseases have been neglected, resulting in a sharp rise. In 2002, heart disease, cancer, respiratory disease and diabetes were responsible for 46% of all deaths in developing countries, and by 2030 it is predicted they could be claiming 37million lives every year.

Traditionally the rise in chronic diseases has been attributed to an overall ageing of the population. For the first time, however, the Cambridge research offers statistical evidence that they are more likely to be linked to the rapid lifestyle changes that have occurred with increasing Westernisation.

As average earnings, foreign investment and urbanisation have gone up, Stuckler argues, people have begun to smoke more, drink more and take less exercise. As work has become more office-based and less physical, the population has become more sedentary. The appearance of global restaurant chains known for selling fatty foods, which are both affordable and regarded as "desirable" because of their association with the affluent West, has encouraged people to eat less healthily than before.

To test this theory, Stuckler measured the chronic disease mortality rates of 56 countries against data showing average earnings, economic growth and foreign direct investment. He found that in poorer countries such as Bangladesh, Brazil, Ghana, India and Senegal, a rise in these economic signs of "Westernisation" was accompanied by a rise in chronic disease deaths.

The result could be devastating not only in terms of public health but also economically. Because chronic diseases often kill and disable people who are still of working age, the workforce in these countries will be less able to push productivity forward. In the nightmare scenario, that could create a classic "poverty trap", preventing the country from being able to afford the resources that would enable it to combat the disease in the first place.

By comparing the rise in chronic disease death rates with the change in Gross Domestic Product per capita, the research shows that for every 10% increase in chronic diseases the country suffers a 0.5% decline in its economic growth rate. In Latin America, for instance, where in 2002 the annual predicted increase in chronic diseases over the next 28 years was 48%, economic growth could therefore be slowing down by 2.2.% year-on-year by 2030.

Stuckler argues that to stop the crisis from becoming any worse, international organisations, charities and governments should collaborate in developing a world health programme that focuses on both infectious and chronic diseases. Foreign investors should also be encouraged to promote healthier living in the developing world.

"Health organisations have done wonders in fighting the problem of disease in developing countries, but the fact remains that for every $1 spent on fighting chronic diseases, $15 are spent on infectious disease," Stuckler said.

"The global challenge these organisations now face is how to act in concert to tackle the rising rate of chronic disease without discouraging equitable and sustainable economic development. Public health in these countries and internationally must transform itself if we are to avoid the lives we save in the battle against infectious disease being lost prematurely to chronic diseases instead."

University of Cambridge