December 13, 2012
The goal of this study is to calculate what proportion of deaths or disability‐adjusted life years (DALYs) can be attributed to specific risk factors, holding other independent factors unchanged. Quantification of the disease burden caused by different risks informs prevention by identifying which risks make the greatest contribution to poor health. No complete revision of global burden of disease caused by risk factors has been done since a comparative risk assessment in 2000, and no previous analysis has assessed changes in burden attributable to risk factors over time.
For each risk factor, the fraction of the population in each country, age, sex, and year exposed to that risk is estimated using all available published and unpublished data. The harm associated with each risk is based on an analysis of all published studies. Prevalence of exposure and harm from each risk is then used to estimate deaths, years of life lost due to premature mortality (YLLs), years lived with disability (YLDs), and DALYs attributable to the independent effects of 67 risk factors by age, sex, and region for two points in time – 1990 and 2010.
In 2010, the three leading risk factors for global disease burden were high blood pressure (7% of global DALYs; 9,395,860 deaths); followed by tobacco smoking, including secondhand smoke (6.3% of global DALYs; 6,297,287 deaths); and alcohol use (5.5% of global DALYs; 4,860,168 deaths). This reflects a substantial change from 1990 when the leading risk factors were childhood underweight (7.9%; 2,263,952 deaths); followed by household air pollution from use of solid fuels (7%; 4,579,715 deaths); and tobacco smoking, including secondhand smoke (6.1%; 5,329,808 deaths).
Regional differences are significant. While much of the world is burdened by obesity and high body mass index, underweight is still the leading risk factor in sub‐Saharan Africa. Other prevalent risk factors in the region include household air pollution and nonexclusive and discontinued breastfeeding.
Although child undernutrition has fallen significantly as a risk factor for all ages, it remained the leading risk factor worldwide in 2010 for children under 5, accounting for 12.4% of global DALYs, followed by nonexclusive or discontinued breastfeeding at 7.6%.
A number of risks that primarily affect childhood communicable diseases, including unsafe water and sanitation and micronutrient deficiencies, declined in significance in the past 20 years, with unsafe water and sanitation accounting for only 0.9% of global DALYs in 2010.
At the same time, GBD 2010 findings show the importance of household air pollution from solid fuels and ambient particulate matter pollution as major risk factors. One or both rank in the top 10 as causes of disease burden in 13 of the 21 regions. In south Asia, they are the leading cause of burden.
The findings indicate that there is increasing burden from high blood pressure, high body mass index, and high blood sugar. Dietary risk factors and physical inactivity collectively accounted for 10.2% of global DALYs in 2010, which puts it in the same tier as tobacco smoking, alcohol use, or childhood malnutrition individually. For this reason, policies that effectively encourage or facilitate lifestyle changes, especially a more balanced diet and increased physical activity, would likely have a significant impact on health.
About tobacco in particular, it is worth noting that despite sustained public health campaigns about the negative effects of tobacco, it remains one of the top risk factors globally and in nearly every region. That lack of change is due to declines in smoking in high‐income countries being replaced by increases in developing countries.
Blood pressure also merits special attention. Blood pressure ties directly to diet, especially increased salt content in food, but it also ties to failures in primary care to adequately detect and treat high blood pressure, particularly in people who are dealing with multiple health conditions.
The study’s findings also suggest that a large burden of disease in many parts of the world is attributable to particulate matter pollution, which is substantially higher than estimated in previous analyses. This demonstrates the need to design alternative fuels for household cooking and heating, implement more stringent regulation of vehicle and industrial emissions, reduce agricultural burning and land clearing by fire, and curb and reverse deforestation and desertification.
Worldwide, the contribution of different risk factors to disease burden has changed substantially, with a shift away from risks associated with communicable diseases in children toward those associated with noncommunicable diseases in adults. It is important to note that the relative impact of risk factors in different regions changes markedly, which means it is unlikely that one common set of policy recommendations globally is the best way to reduce risk factors. Regional tailoring of policies would be a more effective approach.
In sub‐Saharan Africa, for example, risks such as childhood underweight, household air pollution, and insufficient breastfeeding continue to cause a disproportionate amount of health burden, despite a noticeable decline. In contrast, the shift toward noncommunicable disease risk factors has been dramatic in east Asia, north Africa and Middle East, and Latin America.
Lim SS, Vos T, Flaxman AD, et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. The Lancet. 2012 Dec 13; 380: 2224–2260.