WHO Says 20 Hazards Affect All Nations
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By D avid Brown
Washington Post Staff Writer
Thursday, October 31, 2002; Page A16
About half of the premature deaths worldwide are caused by 20 health hazards that if modified or avoided could produce substantial increases in life expectancy in every country and huge ones in many, according to an ambitious new accounting by the World Health Organization.
Nearly one-third of early death and disability stems from nutritional or dietary causes, including too little food in the poorest countries and too much (or the wrong kind) in the richest. Inadequate intake of three key "micronutrients" -- zinc, iron and vitamin A -- is responsible for an unexpectedly high burden of disease, the authors of the report found.
In perhaps the most unexpected finding, the international research team determined that three conditions -- high blood pressure, elevated cholesterol and tobacco use -- are among the top 10 risk factors for early death in essentially all countries. Previously, those hazards were thought to be important only in relatively affluent nations.
Many of the findings are predictable. Malnourishment is the leading cause of shortened life, as has probably been the case for thousands of years. It primarily affects children and women of reproductive age, increasing their risk of dying from infectious diseases and birth-related problems. Relatively overlooked hazards turn out to be important. Among them is indoor smoke that arises from cooking, which increases the incidence of pneumonia in children, and emphysema and lung cancer, particularly in women.
"There is a bunch of fairly surprising things we found," said Christopher J.L. Murray, a physician and epidemiologist at WHO. He co-led a team of more than 100 researchers and statisticians from dozens of countries.
The findings appear in a 248-page report from WHO in Geneva. A summary version appears as an article in this week's issue of the Lancet.
Ten years ago, Murray and his chief collaborator, Alan D. Lopez, also of WHO, published the first effort to quantify the causes of death and long-term disability -- what they called the burden of disease -- for the world. This new study steps back into the chain of causation that leads to those outcomes. It attempts to quantify the conditions or risks -- modifiable ones, in particular -- that can lead to disease.
The project is premised on the idea that much (although not all) premature death is avoidable. The research team hopes that by estimating the effect of various risk factors, governments (and to some extent, private companies and organizations) will be able to better produce and target public health campaigns. To that end, the report also estimates the effect various interventions -- everything from food fortification and condom giveaways to tobacco taxes and widespread salt reduction in processed food -- might have on health.
The researchers calculated the amount of disease arising from the various hazards by starting with the total burden of disease determined 10 years ago in the first project, which has been updated. For 14 geographical areas (together comprising the world), they estimated the prevalence of each risk factor, using hundreds of studies as the source of information.
They then determined what fraction of each disease in the region could be attributed to the risk factors. In many cases, this "attributable burden" is easily calculated. Many studies, for example, have shown how much the incidence of stroke will increase as the average blood pressure in a population rises. The researchers also set a "theoretical minimum" for each risk factor. For some, such as tobacco use, it was zero. For others, it was the level at which further drops produce no benefit. (In the case of cholesterol, this was a reading of about 150.) That allowed the team to further estimate what fraction of premature death would disappear if all risks were eliminated.
Some of the estimates involve considerable uncertainty. For some risk factors (such as dietary intake of fruits and vegetables, or amount of physical activity), there are many countries with little or no data. For some hazards, there is uncertainty about the relationship between risk and disease -- for example, the extent to which sexual abuse in childhood contributes to mental illness in adulthood. The effect of hazards can also differ from place to place, with alcohol contributing to violent death more in countries where guns are available than in ones where they aren't.
For developing countries with high child and adult mortality (most of Africa, Pakistan, India and a few Latin American and Caribbean countries), insufficient dietary protein and calories accounted for about 15 percent of lost years of life. Unsafe sex was second, accounting for about 10 percent of lost years -- almost all arising from early death from AIDS. Unsafe water was third, and indoor smoke from burning wood, dung and other substances for cooking was fourth.
Surprisingly, blood pressure, tobacco and cholesterol were the last three on the top 10 risk factors for those poorest nations -- demonstrating that "they are truly global risks," Murray said.
Those three ranked higher in developing countries with low mortality -- a list that includes most of Latin America, the Middle East, Indonesia, Thailand and Oceania. In that group, undernourishment was fourth and being overweight was fifth, showing that those populations are in the middle of "risk transition" toward what is seen in industrialized countries, which includes North America, Europe and Japan.
In those countries, tobacco, blood pressure, alcohol, cholesterol, being overweight, low fruit and vegetable intake, and physical inactivity are the seven leading risk factors -- each arising, at least in part, from modifiable lifestyle.
© 2002 The Washington Post Company