The two-volume set, Comparative Quantification of Health Risks, resulted from WHO’s Comparative Risk Assessment Project, which involved more than 100 international scientists led by HSPH Assistant Professor Majid Ezzati. For four years, the group reviewed scores of studies from different countries, developed methods by which to scientifically compare them, and collectively analyzed the data. Among the authors’ findings are:

• Nutrition plays a key role in health worldwide. Approximately 13 percent of the global disease burden can be attributed to the joint effects of childhood and maternal underweight or micronutrient deficiencies. According to an ongoing analysis, the authors calculated that the problem, called undernutrition, caused at least 4,000,000 deaths of children under the age of five in 2000, and placed children at increased risk of major childhood diseases like pneumonia, diarrhea, and malaria.

• Globally, 4.4 million deaths, or 7.9 percent of deaths around the world in 2000, were related to unhealthy levels of cholesterol, which contribute to cardiovascular disease.

• Removing 20 selected leading global risk factors, such as undernutrition, high blood pressure, air pollution in homes and cities, unsafe sex, and physical inactivity, would add more than nine years to worldwide healthy life expectancy, and about 16 years in the worst-off parts of Africa.

"A major goal was to standardize analysis methods to ensure greater consistency and comparability in using and evaluating scientific evidence across risks," said Ezzati, who was the lead editor of the book. "This will help policymakers and advocacy groups view risk factor exposures and their subsequent health effects more readily and accurately, and relative to other risk factors."

In addition to Ezzati, editors of the volumes are Alan Lopez of the School of Population Health, University of Queensland, Australia; Anthony Rodgers of the Clinical Trials Research Unit, University of Auckland, New Zealand; and Christopher Murray, Richard Saltonstall Professor of Population Policy at HSPH and director of the Harvard Initiative for Global Health.

"There was a huge interest in the development of better information on the comparative magnitude of risk factors," said Murray, who led the Global Burden of Disease project and who has previously served as executive director of the Evidence and Information for Policy Cluster at WHO. "These volumes offer a one-stop source for a systematic overview of the population effects of exposure to risks."

The editors chose specific risk factors based on the following criteria:

• Was the risk factor likely to have large health effects, regionally or globally?

• Was the risk factor potentially modifiable? Could interventions be found or designed to curb the exposure?

• Was there enough research information about the risk factor available?

• Was the risk factor reasonably well-defined? For example, diet is too broad and complex, but the risk posed by a lack of specific nutrients is narrow enough for quantification.

The collection of data is an ongoing effort. "We will want to incorporate new research as it becomes available," said Murray. "There is also a clear interest in taking the approach used in Comparative Quantification of Health Risks and applying it on national levels." Ezzati added that "a major new and policy-relevant direction for the research is to consider the death and disease burden that can be avoided in the future by reducing forecasted risk factor exposure."

Comparative Quantification of Health Risks was published by WHO and can be ordered through the agency’s online bookstore at http://www.who.int/en or at http://www.amazon.com. The preliminary findings of the book were used as a basis for WHO’s World Health Report 2002–Reducing Risks, Promoting Healthy Life, available at http://www.who.int/whr/2002/en/. The Comparative Risk Assessment Project was funded by the National Institute of Aging. A CD-ROM with detailed tables on aspects of disease burden caused by these risk factors accompanies the volumes.