Cardiovascular disease is the leading cause of death in the US and throughout the world. In some parts of the world both incidence and mortality from coronary heart disease and stroke continue to rise, particularly in developing countries. In many Western countries, however, after a steady increase through much of the 20th century, mortality rates began to decline in the 1970s, in part due to advances in medical care. But defibrillators, surgery, and drugs are only partly responsible. Preventive measures, including public health interventions that collectively re-shape system conditions influencing the health of entire populations, have also played a major role.
One well-documented project was undertaken in Eastern Finland, where cardiovascular mortality was an urgent concern. Residents and government officials in North Karelia designed what turned out to be successful, pioneering, integrated interventions that can teach important lessons about how to reduce not only cardiovascular disease but also other complex disorders in entire populations.
In 1947, Vaino Kannisto, a Finnish graduate student, showed in his doctoral thesis that heart disease mortality had been far higher in Eastern Finland than in western regions for decades. In fact, Eastern Finland had the highest heart disease mortality in the world. At about the same time that Kannisto published his thesis, several longitudinal studies, including the famous Framingham Heart Study, began to identify risk factors that seemed to make cardiovascular disease more likely. Leading most lists were increased levels of serum cholesterol, high blood pressure, and smoking. Each of these independently correlated with increased risk—which increased even more as they were added together.
Meanwhile, investigators documented differences in diet, serum cholesterol, smoking, and blood pressure among men in the two regions in Finland. Based on what they knew at the time, the Finnish Heart Association, along with many partners, launched the North Karelia Project, a region-wide effort to change behaviors with the aim of reducing these risk factors and mortality from heart disease in Eastern Finland.
Planners quickly recognized that lifestyles are not just features of individuals but are imbedded in cultural, social, and physical aspects of communities. As a result, the North Karelia Project designed multi-level interventions with the ultimate goal of reducing smoking, elevated serum cholesterol, and elevated blood pressure in the entire population—not just in people at highest risk. Major emphases were on general lifestyle changes, especially smoking and dietary habits, for everyone.
Public health practitioners have long recognized the benefits—or risks—associated with small shifts in determinants of health within populations. In 1985, epidemiologist Geoffrey Rose observed that a large number of people at a small risk will give rise to more cases of a disease than a small number of people at a large risk. “The causes of cases of a disease in individuals”, he said, “differ from the causes of incidence of that disease in a population. Why some individuals have hypertension is a different question from why some populations have much hypertension, while in others it is rare.”
Rose was interested in strategies for disease prevention. He recognized that small downward population-wide shifts in blood pressure where hypertension was common could have large public health benefits. Community-level interventions could also reach more people and added to what individuals could do to accomplish the same goal.
The North Karelia Project put these ideas to work. Population-wide efforts to reduce smoking, cholesterol, and blood pressure involved not only individual education and treatment but also extensive work with the media, schools, supermarkets, the dairy industry, agriculture, and civic organizations.
The results were dramatic. In 35 years the annual age-adjusted coronary heart disease mortality rate among 35-64 year-old men declined 85 percent. Cancer-related mortality was also reduced, and all-cause mortality reduced for men and women.
One early commentary on the North Karelia Project derisively called it “shot-gun prevention.” But, it worked. It showed the value of multi-level interventions in an entire population—shifting system conditions for everyone—rather than focusing on individuals at highest risk. Data from five different surveys showed that an estimated 20 percent of the coronary heart disease mortality could be prevented by reducing cholesterol levels in the entire population by 10 percent, while a 25 percent cholesterol reduction in only those with the highest levels would reduce morality by only five percent. Lifestyle changes, they concluded, are not just responsibilities of individuals but also of communities.
The North Karelia Project shows that strategically-designed community- and societal-level interventions can have population-wide benefits that far exceed those gained by focusing only on individuals at risk. They shift societal norms so that more people encounter healthier environments in which to live their entire lives.
In the US, community-based and national tobacco control programs, bans on hazardous products like leaded gasoline, and clean air, safe drinking water, and zoning laws are other examples showing similar benefits. But, efforts to enlist social, political, and economic forces to improve public health usually generate clashes of values, interests, and ideologies. It’s messy but the health of this and future generations undeniably depend on how these conflicts are resolved.
Puska P. The North Karelia Project: From N Karelia to National Action. Available at http://www.julkari.fi/bitstream/handle/10024/80109/731beafd-b544-42b2-b853-baa87db6a046.pdf?sequence=1
Rose G. Sick individuals and sick populations. Int J Epidemiol. 1985; 14(1):32-38.
Editorial: Shot-gun prevention? Int J Epidemiol. 1973; 2(3):219-220.