I brought this picture of a triangle to Thanksgiving this year. It helped me explain what public health is to distant relatives who don’t understand what I’m going to school for. I struggle to articulate it every year, so this time I relied on the aid of a diagram developed by a seasoned professional: Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention.
The triangle is actually a pyramid. It's called The Health Impact Pyramid. The pyramid is hierarchical and has five tiers. The most impactful types of public health interventions are at the bottom, the least impactful are at the top. Accompany me on a descent down the pyramid, similar to what I served to relatives on Thanksgiving.
At the tip of the pyramid are educational interventions. These are generally the most common, but least effective, types of public health interventions. Examples of note include: D.A.R.E., graphic cigarette warning labels (if they were allowed), calorie counts on menus, and the other, more famous, three dimensional triangle in public health—the food pyramid. Educational interventions are based on the idea that people will do healthy things if they know what’s good for them and what’s not. While these interventions work for some people, they don’t for most in the absence of supporting environmental changes. Even if little Johnny learns that exercise is good for him, he’s unlikely to run and play if the park is ridden with broken glass and scary people selling drugs. Video games will probably remain a safer, but more sedentary, activity.
Clinical interventions reside at the next level of the pyramid. These usually require a visit to a doctor’s office and include things such as screening and treatment for osteoporosis to prevent bone fractures, HIV treatment to reduce viral load and the chances of transmitting the virus, and electronic medical records that improve the coordination of medical care. Although they have preventive benefits, interventions in this category fall short because they reach individuals one at a time – not a population all at once. They also aren’t always effective and don’t benefit people without access to a regular source of health care, such as those who are under or uninsured.
In the middle of the pyramid are long-lasting protective interventions. Immunizations, which prevent 2.5 million children's deaths a year, are the archetype example here. While these interventions also reaching people only an individual basis, they are extremely effective and confer long-lasting benefits.
The focus shifts from the individual to the population as we move down to interventions at the widest two levels of the pyramid—the magnitude of their impact increasing as a result. First are interventions that change contexts to make healthy decisions the default. Here, people need to go out of their way to avoid the benefits, regardless of their income, level of education, or health insurance status. Examples are numerous: clean air, fluoridated water, cars with airbags, foods without artificial trans-fat, paint without lead, iodized salt, smoke-free workplaces, and built sidewalks, to name a few. Law and public policy decisions, such those that regulate private sector behavior and invest in infrastructure, are the public health tools that make these interventions possible.
At the base of the pyramid are interventions that address socioeconomic factors. Research has long told us that poverty, education, housing, and income inequality are the most powerful determinants of health. In the year 2000 alone, researchers estimate, 245,000 deaths in the U.S. were attributable to low education, 130,000 to level poverty, and 119,000 to income inequality. While these issues are often viewed as intractable social problems, and beyond the purview of public health, interventions such increasing the minimum wage, enforcing the international human right to a basic standard of adequate living, and publicly funded early childhood education can have profound effects on human health.
While public health impact increases with each descending level of the pyramid, so does complexity. Handing out pamphlets about healthy diet is not politically contentious; upheaving institutionalized arrangements of power and property to reduce social inequality, is. Even less extreme interventions, such as environmental regulation and smoke free policies, often encounter political resistance and legal roadblocks. It also becomes more challenging to quantify an intervention’s effects at the lower levels of the pyramid. Randomized controlled trials make it easy to evaluate the precise impact of an educational or clinical intervention. It’s more difficult to isolate the impacts of laws and policies from other factors that could have produced a change.
The construction of a pyramid is a fitting analogy for public health. Like ancient Egyptians who quarried stone, public health practitioners conduct science to create the building blocks for something that benefits society. Neither stones nor scientific knowledge have much value in and of themselves—they need to be strategically pieced together. Like a 10-ton block of limestone, science can be hard to move forward. Sometimes public health practitioners advance only as far as a pamphlet. But we’re always working to build structures within society that promote health across a population and withstand the test of time.
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