The epidemiological transition is now spreading to the emerging world

A CHILD BORN in China today can expect to live more than three decades longer than his ancestors 50 years ago, a gain in life expectancy that rich countries typically took twice as long to achieve. The increase reflects a shift in the burden of disease that is increasingly apparent in other developing countries, too. But the speed of the transition brings with it huge challenges for both domestic policymakers and the international organisations that distribute aid and run health programmes.

Crudely put, what is known as “the epidemiological transition” is a shift from diseases of the bellies and lungs of babies to those of the arteries of adults. In 1990 the main causes of premature loss of life in 16 of China’s 33 provinces were either respiratory infections or complications of pre-term births. By 2013 the leading cause in 27 provinces was cerebrovascular disease.

This change is documented by the Global Burden of Disease Study, produced by the Institute for Health Metrics and Evaluation (IHME) based at the University of Washington in Seattle. As well as crunching the numbers for death rates and life expectancy at birth, the IHME tracks “disability-adjusted life years” (DALYs), an estimate of the time lost to disability and early death. By measuring DALYs, it can work out the number of years people can expect to live free from disability.

The Global Burden of Disease Study is imperfect. For every death for which data are available, it has to make assumptions about many more. Its alphabet soup of measures can be unappetising. But it offers the best picture available of the world’s health. Between 1990 and 2016, the global average for healthy life expectancy at birth increased from 55 to 61 years for men and from 58 to 65 years for women. The rise was due mainly to lower rates of infectious diseases such as HIV/AIDS, malaria and tuberculosis, as well as fewer neonatal deaths. Between 2006 and 2016, years of life affected by disease or early death fell by 44% for HIV/AIDS, 27% for malaria and 23% for tuberculosis. For neonatal disorders the drop was 23%. Separate data from the WHO show that death rates from these causes fell sharply between 2005 and 2015. HIV/AIDS still kills more than 1m people every year, but since 2014 it has not appeared in the global list of the ten most common causes of death.

Meanwhile the burden of chronic conditions has been rising. The number of DALYs due to diabetes and kidney disease has gone up by 24% and 20% respectively since 1990. In a survey last year the World Bank and the WHO found that more than 1bn people globally have uncontrolled hypertension, a risk factor for many non-communicable diseases. Even though health spending per person in China increased by 12% a year between 1993 and 2012, studies suggest that over half of Chinese with hypertension may be unaware of their condition. Globally, mental illness has become more common, too. In 2016 major depressive disorders were among the top ten causes of ill health in all but four countries worldwide.

Another way of looking at the shift is to examine the main causes of DALYs in countries of different income levels. In the poorest fifth of countries the four most common causes are lower respiratory infections (such as pneumonia), malaria, diarrhoea and HIV/AIDS. In middle-income countries they are heart disease, conditions to do with blood supply to the brain, road accidents and lower back and neck pain.

So developing countries will have to deal with two problems simultaneously. The first is that the absolute numbers of people with infectious diseases remains high. Nigeria has more than a quarter of the entire world’s malaria cases, for example. The second is that people are living longer, but not necessarily in a healthy state, as already evident in the rich world (see chart).

DALY bread

Shifts in the burden of disease also present dilemmas for international organisations. Though most spending on health in poor countries comes from government budgets and out of consumers’ pockets, an average of just over a third in 2016 was paid for by aid. Health aid in that year added up to $37.6bn, according to the IHME. A little over half of that came from three sources: the American government (34.0% of the total), the British government (10.9%) and the Gates Foundation (7.8%). The vast majority of this aid goes on child and maternal health and on infectious diseases, especially HIV, which makes up fully 25% of the total. Non-communicable diseases account for just 1.7%.

Those diseases also get minimal attention from the biggest institutions in global health. The World Bank and the WHO, both set up in the 1940s, have a sprawling array of interests. Two newer organisations, the GAVI Alliance, which funds vaccines, and the Global Fund to Fight AIDS, Tuberculosis and Malaria, are chiefly concerned with infectious diseases.

“Improving global health is no longer primarily about combating infectious diseases,” says Lawrence Summers, who as the World Bank’s chief economist in the 1990s did much to advance its work on health. That view may strike many health experts as premature when malaria, tuberculosis and HIV are still killing millions every year, but the epidemiological shift will ensure that ever more resources will be consumed by chronic conditions. Policymakers will have to think carefully about which health services to prioritise, and how best to supply them.