Haddon Matrix: Getting The Message Across

The Haddon Matrix is a tried and trusted tool for thinking about managing risk, particularly in public health. The basic matrix contains 3 key elements: the host, the agent (or vehicle) and the environment (subdivided into physical and social). These form the columns of the matrix. The rows refer to pre-event, the event and post-event activities.

	HOST	AGENT	ENVIRONMENT
PRE-EVENT
EVENT
POST-EVENT

In a previous post I illustrated this with a road traffic accident example as below.

This is useful but does it get across two important aspect when trying to manage risk: which of the cells in the matrix is the most significant AND which of the cells is it most effective to try to influence?

Not all the cells and their contents affect the risks of a hazard equally. From public health take the example of smoking - it could be argued that the social and cultural norms that an individual grows up in have a huge impact on their propensity to smoke. The host or individual smokes but what chance did they have given their environment. In other words the environment cells, particularly pre-event (the event being the cancer caused by smoking) has a massive impact on the risk. Likewise, survival of the event depends greatly on the level of health care available including catching the cancer early on, so both the event and post-event are greatly influenced by the environment. Visually the Haddon Matrix might look as below.

	HOST	AGENT	ENVIRONMENT
PRE-EVENT
EVENT
POST-EVENT

This alteration of cell size to match the perceived level of influence of host, agent and environment can help to get across the message as to which of the three is most important.

A second aspect, however, is which of the different elements to try to influence. It could be argued that changing a social or cultural environment is a long-term and difficult process but the one that has the greatest imapct on smoking levels. Effectiveness cna be defined in many ways and it maybe that in the short term targeting the host to change their behaviour is much easier (and cheaper) to produce and places responsibility firmly in the lap of the person smoking. As well as being cheap for health authorities and potentially politically more palatable as it highlights individual responsibility (depending on your political persuasion) altering cells sizes to reflect this, as below, does highlight to the individual that they do have potential control over their fate (whether this is an illusion or not is another question).

	HOST	AGENT	ENVIRONMENT
PRE-EVENT
EVENT
POST-EVENT

So for risk analysis and management maybe it is worthwhile changing the sizes of the cells when discussing both degree of influence and effectiveness of potential actions however this is defined. This may help in targeting resources effectively for the ends in mind.