WHO’s upcoming report Global health risks identifies the global and regional mortality and disease burden associated with 24 health risks, which range from environmental risks such as exposure to smoke from indoor solid fuel use, to metabolic risks such as high blood pressure.
The report finds that five leading risk factors (childhood underweight, unsafe sex, alcohol use, unsafe water and sanitation, and high blood pressure) are responsible for one-quarter of all deaths in the world and one-fifth of all disability-adjusted life years (DALYs). Success in reducing exposure to these five risk factors alone would increase global life expectancy by nearly five years.
The report describes the changing risk profiles of developing countries. Global health risks are in transition as declining fertility rates and fewer deaths from infectious diseases at young ages are reflected in population age patterns with a predominance of older people. At the same time, patterns of physical activity, diet, alcohol and tobacco consumption are changing. Low- and middle-income countries now face increasing burdens of chronic, noncommunicable conditions in addition to infectious diseases.
A challenging task
The analysis of risk factors is challenging due to the inherent complexity of finding and interpreting evidence on risks and their causal associations with disease and disability. Risk assessment is limited both by epidemiologic knowledge and by availability of global information on risk factor exposure. To carry out a quantitative risk assessment, evidence must exist first, to show that the exposure to each risk causes disease, second, to quantify the magnitude of harm caused by each exposure, and lastly, to assess the presence of each risk in the population globally.
Some risk factors are easier to assess than others. Exposure to biological risks such as high body mass index (BMI) or vitamin deficiencies can be measured with relatively little error, and can be linked to disease outcomes on an individual basis. In contrast, it is more difficult to precisely measure exposure to dietary, environmental and behavioural risk factors.
For these risks, the lack of precise measurements makes it more challenging to link exposures to disease incidence. Because it is more difficult to generate epidemiological evidence about dietary, environmental and behavioural risk factors, they are less likely to be included in a comparative risk assessment. When included, their burden may be estimated with more uncertainty than for risks that are easier to measure. This inevitably produces a set of estimates for risk factors that are not perfectly comparable and must be interpreted carefully.
A comprehensive revision and update of the health burden attributable to risk factors is now under way as part of the Global Burden of Diseases, Injuries and Risk Factors study. The new study will quantify the effects of risk factors for 1990 and 2005, allowing for an analysis of trends in exposure of and effects of risks, and will include additional risk factors, such as salt intake, folic acid deficiency and intimate partner violence. Comparative risk assessment methods will continue to evolve as new epidemiologic evidence becomes available.
The report finds that five leading risk factors (childhood underweight, unsafe sex, alcohol use, unsafe water and sanitation, and high blood pressure) are responsible for one-quarter of all deaths in the world and one-fifth of all disability-adjusted life years (DALYs). Success in reducing exposure to these five risk factors alone would increase global life expectancy by nearly five years.
The report describes the changing risk profiles of developing countries. Global health risks are in transition as declining fertility rates and fewer deaths from infectious diseases at young ages are reflected in population age patterns with a predominance of older people. At the same time, patterns of physical activity, diet, alcohol and tobacco consumption are changing. Low- and middle-income countries now face increasing burdens of chronic, noncommunicable conditions in addition to infectious diseases.
A challenging task
The analysis of risk factors is challenging due to the inherent complexity of finding and interpreting evidence on risks and their causal associations with disease and disability. Risk assessment is limited both by epidemiologic knowledge and by availability of global information on risk factor exposure. To carry out a quantitative risk assessment, evidence must exist first, to show that the exposure to each risk causes disease, second, to quantify the magnitude of harm caused by each exposure, and lastly, to assess the presence of each risk in the population globally.
Some risk factors are easier to assess than others. Exposure to biological risks such as high body mass index (BMI) or vitamin deficiencies can be measured with relatively little error, and can be linked to disease outcomes on an individual basis. In contrast, it is more difficult to precisely measure exposure to dietary, environmental and behavioural risk factors.
For these risks, the lack of precise measurements makes it more challenging to link exposures to disease incidence. Because it is more difficult to generate epidemiological evidence about dietary, environmental and behavioural risk factors, they are less likely to be included in a comparative risk assessment. When included, their burden may be estimated with more uncertainty than for risks that are easier to measure. This inevitably produces a set of estimates for risk factors that are not perfectly comparable and must be interpreted carefully.
A comprehensive revision and update of the health burden attributable to risk factors is now under way as part of the Global Burden of Diseases, Injuries and Risk Factors study. The new study will quantify the effects of risk factors for 1990 and 2005, allowing for an analysis of trends in exposure of and effects of risks, and will include additional risk factors, such as salt intake, folic acid deficiency and intimate partner violence. Comparative risk assessment methods will continue to evolve as new epidemiologic evidence becomes available.
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