In 1990, physician and health economist Christopher Murray at Harvard University and medical demographer Alan Lopez at the World Health Organisation embarked on the first ever attempt to measure the global burden of disease and developed the now-famous Disability Adjusted Life Year (DALY) metric that made it possible to combine estimates of mortality and morbidity burden around the world. DALY is the sum of years lived with disability [YLD] and years of life lost [YLL].
Since then, there have been estimates in 1999 to 2002 and 2004. But the latest iteration of the project, Global Burden of Disease 2010, has been on a different scale, involving nearly 500 researchers from more than 300 institutions in 50 countries. It is the largest ever systematic effort to describe the global distribution and causes of a wide array of major diseases, injuries, and health risk factors.
Twenty years ago, the project assessed the burden of 107 diseases and injuries and ten selected risk factors for the world and eight major regions over one calendar year. Now, thanks to advances in technology, the availability of data, and the participation of experts around the world, as well as the leadership of a core group of researchers, the scope has increased to 291 diseases and injuries in 21 regions, for 20 age groups, and an estimation of trends from 1990 to 2010. Global Burden of Disease 2010 also includes an assessment of 67 risk factors.
The results, published yesterday in seven articles in The Lancet, are set to shake up health priorities across the world.
In summary, the analysis shows that infectious diseases, maternal and child illness, and malnutrition now cause fewer deaths and less illness than they did twenty years ago. As a result, fewer children are dying every year, but more young and middle-aged adults are dying and suffering from disease and injury, as non-communicable diseases, such as cancer and heart disease, become the dominant causes of death and disability worldwide. Since 1970, men and women worldwide have gained slightly more than ten years of life expectancy overall, but they spend more years living with injury and illness.
There were 52.8 million deaths in 2010 compared with 46.5 million deaths in 1990. Of these, 12.9 million were from ischaemic heart disease and stroke, or one in four deaths worldwide, compared with one in five in 1990. Cancer claimed 8 million lives in 2010 compared with 5.8 million in 1990; trachea, bronchus and lung cancer accounted for 20% of these. Twice as many people died of diabetes in 2010 – 1.3. million – than in 1990, which is higher than deaths from tuberculosis or malaria (1.2 million each). Deaths from HIV/AIDS increased from 0.30 million in 1990 to 1.5 million in 2010, reaching a peak of 1.7 million in 2006. The fraction of global deaths due to injuries (5.1 million deaths) was marginally higher in 2010 (9.6%) compared with two decades earlier (8.8%). This was driven by a 46% rise in deaths worldwide due to road traffic accidents (1.3 million in 2010) and a rise in deaths from falls.
The contributions of risk factors to regional and global burden of diseases and injuries has shifted substantially between 1990 and 2010, from risk factors that mainly cause communicable diseases in children to risk factors that mainly cause non-communicable diseases in adults.
The proportion of overall disease burden attributable to childhood underweight – the leading risk factor worldwide in 1990 – had more than halved by 2010, making childhood underweight the eighth risk worldwide, behind six behavioural and physiological risks, and household air pollution from solid fuels. Other risks for child mortality, such as non-exclusive and discontinued breastfeeding, micronutrient deficiencies, and unimproved water and sanitation, have also fallen. However, child and maternal undernutrition risks collectively still account for almost 7% of disease burden in 2010, with unimproved water and sanitation accounting for almost 1%.
Of the non-communicable disease risks, high blood pressure, high body-mass index, high fasting plasma glucose, alcohol use, and dietary risks have increased in relative importance. This overall shift has arisen from a combination of the ageing population, substantial achievements in lowering mortality of children aged younger than 5 years, and changes in risk factor exposure.
These broad global patterns mask enormous regional variation in risks to health. In sub-Saharan Africa, risks such as childhood underweight, household air pollution from solid fuels, and suboptimal breastfeeding continue to cause a disproportionate amount of health burden, despite decreasing. The shift to risk factors for non-communicable disease was clear in east Asia, North Africa and Middle East, and Latin America.
For people aged 15 to 49 years, the leading risk factor worldwide was alcohol use, followed by tobacco smoking including second-hand smoke, high blood pressure, high body-mass index, diet low in fruits, drug use, and occupational risk factors for injuries. Risk factor rankings in this age group stayed broadly similar between 1990, and 2010, with the exception of iron deficiency, which dropped from the fourth leading risk factor in 1990, to ninth in 2010.
High blood pressure, tobacco smoking including second-hand smoke, alcohol use, and diet low in fruits were all in the top five risk factors for adults aged 50 to 69 years and adults older than 70 years, in both 1990, and 2010, accounting for a large proportion of disease burden in both age groups. Globally, high blood pressure accounted for more than 20% of all health loss in adults aged 70 years and older in 2010, and around 15% in those aged 50 to 69 years. Tobacco smoking including second-hand smoke accounted for more than 10% of global disease burden in each of these age groups in 2010.
Globally, the sum of years lived with disability and years of life lost (DALY), was influenced most by dietary risk factors and physical inactivity – together these were responsible for 10% of the global disease burden in 2010.
Of the individual dietary risk factors, the largest attributable burden in 2010 was associated with diets low in fruits (4.9 million deaths), followed by diets high in sodium (4.0 million deaths), low in nuts and seeds (2.5 million deaths), low in whole grains (1.7 million), low in vegetables (1.8 million deaths), and low in seafood omega-3 fatty acids (1.4 million deaths). Physical inactivity and low physical activity accounted for 3.2 million deaths.
This impressive analysis of global health issues by Christopher Murray and colleagues provides much reason for hope but also challenges the current medical paradigm and global healthcare system.
It shows clearly that the focus of global health authorities in recent decades on reducing infection and malnutrition has paid off – life expectancy has increased almost everywhere. This focus needs to continue to minimise incidence of diseases like tuberculosis, malaria and HIV/AIDs.
It also reveals, however, that the leading causes of death in the modern developed world are conditions which cannot be controlled by vaccinations, antibiotics, improved sanitation or insecticides. The data provide evidence that the risk factors for non-communicable diseases like heart disease, cancer and diabetes, are predominantly related to poor diet and lifestyle.
The large attributable burden for dietary risk factors such as diets low in fruits, vegetables, whole grains, nuts and seeds, and seafood omega-3 fatty acids might come as a surprise to some. The large burden is caused by both high exposure, e.g., low intake of fruits and vegetables in many regions – and large effect sizes.
Given the crucial role of dietary and lifestyle factors in determining long-term health, the answer to alleviating the suffering created by these chronic non-communicable diseases does not lie in the current medical model, with its preoccupation with drugs and surgery. Our doctors are trained to relieve symptoms not to address the underlying causes of chronic disease. Powerful commercial interests in the food, pharmaceutical and health sectors drown out the voices of those who can see that the solution is really very simple.
Widespread consumption of plant-based diets, rich in vegetables, fruit, whole grains, beans, nuts and seeds, together with not smoking and more physical activity, would transform people’s lives and radically reduce healthcare costs. It is not rocket science.
Dr Murray, I salute you and your colleagues for a first rate piece of work. May the truths you have exposed become part of mainstream understanding as quickly as possible and lead to a sea change in our approach to health and well-being.
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Murray et al (2012). Global Burden of Disease 2010. The Lancet, 13 December 2012.