Almost half of the world's people call the tropics home. The region hosts most of the world's cultural and linguistic diversity, including many of the oldest cultures on Earth, and some of the largest and fastest growing cities. Although nations in the tropics have made considerable progress in recent decades, there is marked variation in standards of living between regions, and many communities continue to suffer from poverty, poor health outcomes and limited educational opportunities.
Poverty & Urbanisation
Poverty is the pronounced deprivation of well-being due to insufficient income, food and services. It may be both the cause and result of poor health, lack of education, over-exploitation of natural resources, corruption, conflict or poor governance.
Although a limited measure, people living in extreme poverty are those who do not have income or consumption above $1.25 per day. The proportion of the population in developing nations of the tropics living in extreme poverty declined from 51% in 1981 to 28% in 2010. Despite this achievement, more than two-thirds of the world’s population living in extreme poverty lives in the tropics. There is considerable variation in rates of poverty alleviation between and within regions in the tropics. Most progress has occurred in South East Asia and Central America, but in contrast, the number of people living in extreme poverty in Central & Southern Africa has more than doubled over the past 30 years although the proportion has remained relatively stable.
A larger proportion of people in the tropics also experience undernourishment compared with the rest of the world. Between 1990 and 2012, the prevalence of undernourishment declined in the tropics from 27% to 18% of the population, which compared with a change from 13% to 9% of the population in the rest of the world.
For most of human history people have lived in rural environments but a transition to urban living has been underway since industrialisation. The world’s urban population exceeded the rural population for the first time in 2007. In the tropics, the urbanisation rate has increased considerably faster than globally with an increase from 31% to 45% between 1980 and 2010. However, a greater proportion of people in non-tropical regions (56%) live in cities compared with the tropics.
In 2001, there were around 925 million people living in slums worldwide, equating to 32% of the world’s urban population. The proportion of the urban population living in slum conditions was almost twice as high in the tropics at 46% compared with 24% in the rest of the world. In absolute terms, there were almost 470 million slum inhabitants in the tropics, compared with 460 million in the rest of the world. The proportions were highest for Central & Southern Africa (76%) and Northern Africa & the Middle East (73%).
Education & Employment
Education and employment play central roles in human, social and economic development. Education underpins active and informed citizenship, improves health outcomes and results in a greater range of options for employment. Reflecting its importance to individual empowerment and freedom, education is recognised as a fundamental human right.
Mean years of schooling is an indicator of human capital available in an economy and society. Schooling almost doubled in the tropics between 1980 and 2010. Although in 2010 people in the tropics had 2.5 fewer years of schooling compared with the rest of the world, the rate increased faster in the tropics.
Youth literacy rates increased in all regions of the tropics between the early 1990s and 2010, except for Oceania where it decreased slightly. Overall, literacy rates are consistently lower in the tropics than in the rest of the world.
The global unemployment rate increased slightly between 2000 and 2002 before falling consistently to 2007, in line with stronger economic growth. In 2008 and 2009 the global financial crisis resulted in major falls in economic activity and confidence, and a sharp increase in the global unemployment rate. In the tropics, however, the unemployment rate has declined steadily and only showed a small increase in 2009 before returning to pre-crisis levels.
The World Health Organisation defines health as a state of complete physical, mental and social wellbeing; not merely the absence of disease or infirmity. The biological, psychological and social determinants of wellbeing impact on an individual’s life expectancy and disease burden, which are measurable and provide a degree of insight into health at national and regional levels.
The term ‘tropical health’ is used to describe the unique range of health issues that are primarily prevalent in the tropics and sub-tropics. Climate is a factor in the increased prevalence of some infectious diseases in the tropics , while the relatively poor performance of many tropical nations across a range of social and environmental factors – broadly referred to as the social determinants of health – also contributes to the higher prevalence of many diseases in the region. Undernutrition, overcrowding and limited access to health care are key factors, and a characteristic of health in the tropics is its correlation with broader development inequities.
Life expectancy is comparable across populations, and is one of the most commonly used indicators of a population’s health. Life expectancy increased across all regions of the tropics in the past 60 years, and the gap between the tropics and the rest of the world has narrowed considerably. Nonetheless, in 2010 life expectancy in the tropics was on average 7.7 years lower than in the rest of the world.
Closely associated with development challenges such as poverty, inequality and human rights violations, women’s health is an important indicator of social health. Women are particularly vulnerable to illness and death during pregnancy and childbirth. All regions in the tropics have experienced significant decreases in maternal mortality ratios and child mortality rates. Nonetheless, the tropics represent the vast majority of these deaths, accounting for 76% of maternal deaths and 72% of under-five deaths in 2010.
The adult obesity rate in the tropics is lower than in the rest of the world, but as more people have emerged from poverty in the region, obesity is on the rise, increasing even faster than global trends. Non-communicable diseases are also a growing cause of illness, disability and death in both the tropics and the rest of the world. Many tropical nations face a ‘double burden’ of disease where the prevalence of NCDs is increasing while infectious diseases and undernutrition also remain major public health issues (see more on this issue here).
HIV prevalence among people aged between 15 and 49 years is higher than in 1990 but has stabilised or declined in most regions of the tropics since peaking in the late 1990s. Due to greater access to anti-retroviral therapy, the AIDS mortality rate has been declining in all regions since 2005. Compared with the rest of the world prevalence and mortality rates are much higher in the tropics with most cases occurring in Central and Southern Africa.
Malaria was formerly widespread throughout the world but the disease has largely been eradicated from temperate regions in the last century. Although great progress has been made on eradicating malaria in many parts of the world the disease remains prevalent in much of the tropics. It remains a major health issue, with 96% of cases and 99% of deaths from the disease occurring in the region in 2010.
Dengue is a mosquito borne disease with a large global footprint. It is estimated that around half the world’s population is at risk. While only 2.4 million dengue infections were reported in 2010, WHO estimates that this is a gross underestimate with up to 100 million potential infections worldwide each year. There are no time series data for dengue, but in 2010, 72% of infections occurred in the tropics, with South Asia and South East Asia having the highest number of cases, and the Caribbean the highest incidence rate.
Other neglected tropical diseases such as soil transmitted helminthiases, schistosomiasis and lymphatic filariasis cause significant disability, disfigurement and death, especially in impoverished communities in the tropics.
With the tropics predicted to expand further north and south with a changing climate (see Isaac and Turton's focus essay), malaria, dengue and other NTDs may spread to areas that are currently free of such diseases, including into Europe and the U.S.
Tuberculosis (TB) is believed to have killed more people throughout history than any other microbial pathogen. Although treatable, it remains a serious cause of disability and death throughout the tropics, with the region having 56% of the world's new cases in 2010. Besides Oceania, tuberculosis incidence decreased in all regions between 1990 and 2010. The increase in Oceania is driven by Papua New Guinea which experiences up to 30,000 new cases of TB each year, an estimated 400 of which are multi-drug resistant.
HEALTH IN THE TROPICS
In this State of the Tropics focus essay, Professor Janet Hemingway, Director of the Liverpool School of Tropical Medicine, discusses health care issues in the tropics. While there has been notable progress in tackling health problems in the region, the ongoing burden of infectious diseases, the rise of non-communicable diseases, and limited capacity to generate accurate data are major challenges that need to be addressed.