If you eat right, exercise regularly, and do all the other things health columnists advise you to do, how many years could you add to your life? How much is it worth in terms of extra years to quit smoking, cut back on your favorite cocktail, and substitute a small portion of tofu for a big, juicy steak?
Led by a Harvard researcher, an international team of experts has come up with an answer. It’s a surprisingly large one, an extra six years and eight months of healthy life in the United States or Canada. It’s less if you live in Japan, Australia, or Western Europe, and much more if you live in Africa.
The research team did the first global study of the potential increase in life expectancy if 20 well-known risk factors could be eliminated or reduced to safer levels. These factors include overnourishment and undernourishment, unsafe sex, high blood pressure, elevated cholesterol, tobacco, alcohol and other drugs, polluted water, poor sanitation, and certain on-the-job risks. The study even took into account the indoor burning of coal, wood, and dung, which is common in underdeveloped countries.
Other studies have examined specific risks, like cigarette smoking, or combinations of risks on certain groups of people. “But we wanted to give a picture of what the whole world would look like without these major causes of death and disease,” notes Majid Ezzati, an assistant professor at the Harvard School of Public Health. “Approximately half of deaths and 40 percent of the total health loss worldwide resulted from the joint effects of these risk factors in the year 2000. It was surprising to find out how large the effects of eliminating them were. The increase in healthy life expectancy ranges from 4.4 years in Japan, Australia, and New Zealand to more than 16 years in Botswana, Congo, Kenya, and other parts of sub-Saharan Africa. Think of it, excluding these factors could result in an average gain of more than nine years of perfect health for every person in the world.”
Increasing life expectancy
Ezzati and his team of collaborators from the World Health Organization and various universities throughout the world checked all existing studies on health risks and their consequences that they could locate. These included everything from blood pressure in the United States to smoking in China to malnutrition in Africa. “From this knowledge, we made inferences about what happens to broader populations,” Ezzati notes.
The reliability of information varied from risk to risk and from country to country. Developing nations in Asia, Africa, and Latin America provide good records on childhood malnutrition, unsafe water, and sanitation, but less complete information on blood pressure, alcohol, and obesity. Data on cholesterol and diet from the United States, Canada, and Western Europe are superior to that from Eastern Europe, Africa, and parts of Asia.
“This introduces varying degrees of uncertainty,” Ezzati admits. “Healthy life extension in the U.S. might be six or eight years, rather than 6.7 years. However, our methods and data have been reviewed by more than 150 experts. We believe we used the best scientific evidence and got a good picture of the role of these risks in global health.”
When you account for premature deaths and non-fatal diseases like depression, people in the United States live an equivalent 67.6 years in good health. Adding 6.7 years would bring that to more than 74 years. If other risks not included in the study, like highway injuries and mental illness, are reduced, or their consequences adequately treated, life spans can increase to the 80s or even 90s. (Living 100 years or more requires really good genes, according to another Harvard study.)
People in Western Europe can buy themselves an extra five and a half healthy years at the cost of watching what they eat and drink, exercising regularly, quitting smoking, and reducing their exposure to other risks. Those in Western Europe, Japan, Australia, and other parts of the Western Pacific gain less from risk avoidance than people in the United States and Canada because they are both healthier to start with and have lower levels of risks, Ezzati explains. Healthy life expectancy in Japan, for example, is currently 74 years, almost seven years more than in the U.S.
The researchers hope their findings will motivate national and international agencies and organizations to increase their emphasis on policies and programs that reduce health risks and their consequences. As an example, Ezzati cites raising tobacco taxes, something that is being done in the United States, but not in many developing countries where cigarettes sell for as little as 50 cents a pack. He also favors eliminating sugary snacks, cheeseburgers, french fries, and other unhealthy foods in school cafeterias. In underdeveloped countries, low-cost technologies, like better stoves, can reduce malnutrition and provide clean water and cooking fuels.
“Our study shows that the potential heath gains from reducing major known but often overlooked risks are enormous,” Ezzati says. “The findings highlight the need to address prevention rather than merely treating diseases that are the consequences of nonprevention.”