A person born in North America or Europe in 1900 could expect to live an age of 50.
By 2000, that individual would expect to live an additional 30 years - more than a generation. Most of this gain is attributable to the rise of public health measures and their effectiveness.
Public (also called population) health focusses its strategies on very large groups and populations. Examples of public health strategies include immunizations, smoking cessation, clean water, widespread use of seatbelts and more that have collectively saved millions of lives. Indeed, immunization is credited with saving the lives of 2.5 million children per year globally.
There are many models used to describe the role of public measures.
The traditional depiction of the potential impact of health care interventions is a four-tier pyramid, with the bottom level representing population-wide interventions that have the greatest impact and ascending levels with decreasing impact that represent primary, secondary and tertiary care - each level becoming more individual and less global.
An alternative model, also based on a pyramid, introduced by Thomas R. Frieden, improves on the original by focussing on the impact of each level of intervention. Called the 'health impact pyramid', this model uses five tiers to describe the health impact of different types of public health intervention and provides a framework to improve health. Moving up from the base reflects an increase of individual effort (more individual); moving down from the top shows increasing population impact (more global).
Frieden's tier one, the base of the pyramid, is defined as efforts to address socioeconomic factors, usually called determinants of health, which have the greatest potential to improve health. Among these are socioeconomic status, education, income, living conditions and more.
Tier two is called 'changing the context so that default decisions are the healthy ones. That means introducing conditions where the healthiest choice is also the simplest, the default. Examples include fluoridation: an individual would have to make significant efforts to not benefit if the public water supply is fluoridated. Iodizing salt is another example, as is lowering sodium levels in packaged and restaurant foods with the result of reducing hypertension and heart disease.
Tier three, 'long-lasting protective interventions' described one-time or infrequent interventions that do not require ongoing clinical care. For example, immunizations fit this category.
Tier four represents ongoing clinical interventions which raise the level of commitment needed from individuals yet can have immense health benefits. Unfortunately, poor adherence and imperfect effectiveness reduce overall benefit.
Often perceived as the essence of public health, the top of the pyramid represents health education and counselling. This level usually offers the least effective type of intervention because it demands individual action and healthy choices are not necessarily the simplest, nor the default.
The health impact pyramid effectively describes the various levels of intervention faced by public health systems. Moving up the pyramid reflects decreasing effectiveness, but the higher up the pyramid, the lower the political commitment required. As we move down the pyramid interventions become more significant but harder to implement.
Editor's note: Dr. Paul Martiquet is the medical health officer for rural Vancouver Coastal Health including Powell River, the Sunshine Coast, Sea-to-Sky, Bella Bella and Bella Coola.