Public health interventions shape our everyday lives. While some initiatives are highly visible, others quietly transform our wellbeing in ways most of us never notice. I think of these types of interventions in three main groups: invisible interventions, supported interventions that require individual action and education only interventions. I make the case that the best interventions in terms of effectiveness, participation, sustainability and equity are the invisible ones.

Invisible interventions

Fluoridation is a classic example. If you drink water from the mains system in most parts of Australia, you receive the recommended dose of fluoride every day. You don’t need to understand dental health, pay extra, or remember to do anything. You simply turn on the tap. The benefit is universal and equitable.

Removing lead from paint and petrol is another. Once the policy changed, exposure dropped for the whole population (except for communities where lead smelters remain part of daily life). No behaviour change was required. These interventions succeed because they reshape the environment, not the individual.

The list of these very successful public health interventions is long. Among them are:

• Safe mains water systems
• Sewerage systems
• Waste collection systems
• Cars that protect the occupants in the event of an accident
• Folic acid fortification
• Food safety systems
• Safe infant furniture
• Standard balustrade heights

These interventions require no active decision making to participate and receive the benefit, and they are universally (or near to) distributed across the environments we live in.

Supported interventions that require individual action

Other interventions are part of a well-established system, and are generally well accepted, but require active decisions for participation. Health screening interventions such as blood pressure checks and diabetes screens that occur through the local primary health care service are examples. As an intervention health screens are bolted onto the bigger system of primary health care, supported by a range of different legislation, training, infrastructure and funding systems.

Cancer screening programs go further, with dedicated systems to invite, remind, and track participation. They are accessible, low-cost, and designed for broad reach.

These types of health screen interventions require active decisions for participation. They require a person to prioritise their health when they are still well. They require knowledge about the screening program, trust in the services and to be valued by the people targeted to participate. They often require resources to participate even if they are considered to be ‘free’. This could be the need for transport to get to the service, or to sacrifice work time and associated earnings to participate. Because of this, participation and therefore benefit is uneven.

If we take for example the bowel cancer screening program, we see an overall participation rate in the latest national screening report of 42%, which in itself is a lower than hoped for participation. Aboriginal and Torres Strait Islander people have a lower participation rate of around 38%. Very remote participation was 25% and people from the most disadvantaged socioeconomic quintile had a 36% participation rate. These inequity patterns are repeated across all of these kinds of semi-supported public health interventions.

Despite the interventions being part of a supportive system the need for active participation makes them less effective and equitable interventions.

Education only interventions

Moving down the list to the least effective, is the education only interventions. These try to encourage behaviour change in the substantial absence of a supportive environment. I have written about this in detail in the blog on Educational only approaches are they effective and are they fair. Examples of these are education campaigns, or information resources such as posters or pamphlets. In summary, these kinds of unsupported interventions only work for people for whom it is easy to make the behavioural change. These people are generally highly educated, are financially secure, can prioritise their health and wellbeing, and for whom the campaign messaging directly targets. Even for those who can capitalise on the information to improve their own health, sustainable behaviour change in the absence of a supportive environment is very difficult and generally has a very low effectiveness. For those who cannot act on the messaging, there is no chance of benefit. The effect of these approaches is limited benefit alongside increased inequities in health and wellbeing outcomes.

The pattern is clear: the more an intervention relies on individual effort and resources, the less effective and equitable it becomes.

The ideal public health intervention makes the healthy choice the easy choice — or better yet, the automatic one.