Health systems in developing nations aren't ready for the diseases that accompany ageing, writes Priya Shetty.
Thanks in large part to modern medicine, people are living longer, death rates are lower and the planet's population keeps climbing — it is expected to hit 7 billion this month.
Much of this growth has been, and will continue to be, in the poorer parts of the world, especially in Asia and Africa.
In developing countries, the proportion of people aged 60 years and over is expected to rise from 9 per cent in 2005 to 20 per cent by 2050, according to the UN Population Fund (UNFPA). The WHO estimates that by 2025, three-quarters of the estimated 1.2 billion people aged over 60 will live in developing countries.
With many more people living well into middle age, and more prosperously, global health experts have been concerned about an increasing burden of chronic diseases which, on top of infectious disease killers such as HIV and malaria, have threatened to overwhelm ailing health systems.
Living longer also brings diseases of ageing, such as dementia, Alzheimer's, and Parkinson's disease, which poor nations are woefully prepared to deal with.
Some of the diseases are likely to have different epidemiological patterns in poor countries, and research into interventions must be tailored to these populations.
Mapping the ageing 'epidemic'
Until recently, little had been known about the health of older people, and the prevalence of diseases of old age, in developing countries.
Last year, a joint report by the International Network for the Demographic Evaluation of Populations and Their Health in Developing Countries (INDEPTH) — which gathers demographic data from more than 30 sites in Africa and Asia — and the WHO Study on global AGEing and adult health (SAGE), mapped the health of older people in poor countries for the first time.
The study identified patterns of disease prevalence and risk factors across countries and continents that should help guide research and policy. For instance, older women tend to have worse health than older men. In some regions, such as in parts of Indonesia, older people with the worst health live in semi-urban areas, rather than rural areas.
A key point that the 2010 INDEPTH-SAGE report makes is that industrialised countries have only had to deal with ageing after achieving economic prosperity. But the speed of economic growth in some countries has meant that they are dealing with ageing while still transitioning to a more developed economy.
In India, for example, the segment of the population aged 70 and above, which was only 8 million in 1961, rose to 21 million in 1991 and to 29 million in 2001.
Culture and genetic differences
Even though developing countries can learn some lessons from richer countries about taking care of their ageing populations, there are crucial differences in how ageing will affect them.
In particular, several diseases of ageing involve cognitive decline — and poor countries will have by far the most cases. By 2040, according to the WHO, 71 per cent of 81.1 million people suffering from dementia will be in the developing world.
Efforts to tackle these illnesses must take account of different cultural factors in developing countries. For example, cognitive assessment scales used to measure a change in brain function are now being adapted for a range of languages and cultures, although they are not fully developed for all diseases and populations.
For example, the 10/66 Dementia Research Group, which studies dementia, non-communicable diseases and ageing in low and middle income countries, has developed and validated dementia diagnosis methods that account for variations in language, culture and education in Latin America, Africa, South and South-East Asia, and Russia.
The risk factors for diseases of ageing are also likely to be influenced by genetics and lifestyle, which will require research specific to the developing world. For instance, a variation of the apoE4 gene that increases the risk of Alzheimer's is prevalent in populations in several regions, although not in Sub-Saharan Africa.
Ageing debate: start now
Ageing may seem like a distant concern for developing nations already shouldering the burden of many diseases. But the sheer number of older people who will live in these countries makes a strong argument for dedicating research funds to studying diseases such as Alzheimer's.
Governments will also need to debate how donors should respond to changing demographics. Global aid has traditionally been funnelled into infectious diseases, but should donors also aim to improve the health of ageing populations?
The answer is not yet clear. But developing countries must start to consider the issues.
Efforts to keep people healthy later in life could even pay off economically. If developing countries looked after their ageing populations, they could have a much stronger and well-skilled workforce.
Journalist Priya Shetty specialises in developing world issues including health, climate change and human rights. She writes a blog, Science Safari, on these issues. She has worked as an editor at New Scientist, The Lancet and SciDev.Net.