The World Health Organization says a relatively small number of risks account for a disproportionately large share of death and disease around the world. In a new report, the WHO says addressing these risks with known interventions can extend life span and improve the quality of life.
The common way of measuring illness and death is by listing the number of people who have had diseases or accidents. We say, for example, that tuberculosis kills two million people each year. The World Health Organization still counts that way, of course, but its World Health Report 2002 looks at international health from a different perspective.
"This is a report about risk factors, not about diseases and injuries," says Dr. Charles Murray, the American physician who directed the World Health Report. "We're taking one step back [on] the causal chain and asking, what are the individual behaviors and exposures, what are the environmental exposures that drive the patterns of disease and injury that we see?"
To measure the relative importance of the causes of mortality and sickness, World Health Organization expert working groups reviewed published work, government reports, and international databases.
They identified 10 things that are responsible for nearly half of the 56 million deaths each year. "That allows a focus on preventive strategies to improve human health, in addition to the usual focus on managing disease and injury when it occurs," said Dr. Murray.
The World Health Report's top 10 global health risk factors are:
> Childhood and maternal underweight
> Overweight and obesity
> Unsafe sex
> High blood pressure
> Unsafe sanitation and hygiene
> High cholesterol
> Indoor smoke from solid fuels
> Iron deficiency
Dr. Murray says the prevalence of these problems varies by region. Underweight, nutritional problems, and sanitation dominate poorer areas, while the risks of excess consumption characterize the richer ones. "For the poor countries of the world, there are surprises in the magnitude of indoor air pollution," he said. "Likewise, some of the micronutrient deficiencies are much larger than we have previously appreciated. The biggest surprises, however, are for middle income and high-income countries, where the magnitude of blood pressure and cholesterol as well as alcohol are similar in size to tobacco."
The report estimates that reducing the prevalence of the leading risk factors by just 25 percent would add five to 10 healthy years to life around the world. The poorest regions would experience the most gain, the richest areas the least.
A commentary in the British medical research journal The Lancet praises the WHO for attempting the work. But it warns not to place too much emphasis on the risk rankings. The commentary's authors, John Powles and Nick Day of the Institute of Public Health in Cambridge, England, note that public health surveillance on this scale is a new and immature science. They say reducing certain risk factors may be difficult.
They write that increasing fruit and vegetable consumption, for example, may turn out to be relatively simple compared to the cultural transformation needed to reduce cholesterol in developed countries.
Charles Murray argues that many of the risk factors can be reversed quickly, some with modest changes, and that most benefits would be realized in a decade.
"For each of the risks," he said, "there are things that can be done now and are affordable now. The message is that a lot can be done with existing resources." For example, the World Health Report says poor nations can combat zinc deficiency by adding the nutrient to staple foods like rice and flour. Middle and high-income nations can fight obesity, high blood pressure, and heart disease with a strategy that includes messages to promote exercise and healthy diet and efforts to reduce salt in processed food.
Dr. Murray says adding healthy years to life would not be the only benefit of addressing these risks, noting that "you would also do a lot to reduce inequalities in health within countries because do know that most of these risks are higher or worse in the disadvantaged or poor."