When I mentioned to the editor I was thinking about writing a column on health inequity, she responded by seeking clarification: Did I mean differences in access to health care, in economic status or, perhaps, in genetic make-up?

She hit the nail on the head with each question. Health inequity means different things to different people. It is a loaded term that implies a measure of difference in health between individuals or populations and a degree of social injustice or moral disquiet about that difference.

Not all differences in health are inequitable. Take, for example, differences between men and women in the risk of getting osteoporosis or prostate cancer. These vary by gender but most people would agree these differences are not inequitable and accept the fact some differences are unavoidable. The same might apply to ill health caused by a random genetic mutation: this is unfortunate but not unjust.

On the other hand, health inequalities across social groups, such as class and race, may be considered inequitable because they could reflect an unfair distribution of the underlying social determinants of health. Access to educational opportunities, safe jobs and the social basis of self-respect are common examples.

As well, some people have little free choice about investing in personal health because of financial, social, geographic or time constraints. And early life influences, such as childhood obesity, may have a lingering impact on health as an adult.

Health inequality has long attracted keen attention in the research and policy arena. It is known that public policy can play a role in shaping a social environment that is more conducive to better health.

What distinguishes inequity  as a topic, however, is the moral component. When is an issue a concern about equality in health and when is it an indicator of general injustice in society?

These dimensions can provoke powerful responses in people, such as social indignation and political action, and need to be handled carefully and thoughtfully by the public health practitioner.

Unveiling the ethical dimensions of health inequalities depends very much on how measures of health differences are made. Frameworks have been proposed to guide public health scientists through the steps and questions needed to measure health inequalities and unveil inequities, with logic and consistency.

For example, if we see that the risk of developing diabetes across the lifespan varies in a population, at what point does the distribution of the health issue and the size of the differences become inequitable? Do we measure it by comparing the worst off with the best off? Or by comparing everyone in the population with the average risk in the population? Or by comparing everyone’s risk to a pre-established standard?

Further, what aspect of diabetes should we measure: blood glucose levels, abdominal girth or self-reported diagnoses? Over what time period? And at what level, individual or group?

These comparisons should not be drawn hastily or impulsively. As Max Erhmann advises in his famous script Desiderata, “If you compare yourself to others you may become vain and bitter, for always there will be greater and lesser persons than yourself”. As a science and a system, the vanguards of public health must also take precautions to regulate methods and comparisons in health status in order to avoid fueling ill-founded discontents.

This highlights the importance of epidemiology, the study of factors affecting the  health and  illness of populations. It is considered a cornerstone of public health science. Much like fine art, epidemiological representations require a precise eye, a skillful hand, concentrated effort and a solid frame. It’s the job and responsibility of public health scientists to produce such pictures and to show them to the gallery: for your viewing and consideration.