It's the demography,stupid!

Epidemiology and demography are the two quantitative pillars of public health. Both with Greek origins, epidemiology means literally ‘that which is upon or around the people’, or the human condition, in the same way that the epidermis surrounds the body; while demography relates to the description of the denominator of population. It is on these foundations, together with the social and behavioural sciences, that we are able to acquire the insights to make a difference to protecting and improving population health.

Those insights were captured by Professor Jerry Morris in his book The Uses of Epidemiology, published in 1965, and range from historical study, community diagnosis, the working of health services and understanding individual chances and risks to the identification of syndromes, completing the clinical picture and the search for causes. ¹

While the dynamic nature of public health challenges is apparent from a cursory reflection on all the new problems that have turned up in recent years, as well as those that have faded, the one area of certainty to be found lies in our demographic understanding as represented in the vital statistics of birth and death, of immigration and emigration. Yet that ‘the fish are the last ones to see the water’ is apparent from the number of times we are caught out by failing to digest the implications of a demographic situation and trends that have been with us for some time. I well remember the front page story in the Liverpool Echo some years ago at the beginning of the autumn school term that drew attention to the thousands of classroom reception places; yet, the children who had failed to turn up had not been born five years before.

As with the education system, so with health and the relationship of demography to need and response in the form of prevention, treatment and cure. One of the major phenomena of the post-World War II years around the world has been the impact of the post-war baby boom as a bulge population working its way through life. In England and Wales, the birth population of over 900,000 in 1946–1947 created huge waves as it wound its way through maternity and child health services, into the education system and onwards into adult life. The spin-off in terms of its economic impact and the discovery of the teenager as a major consumer market, together with the pop star ‘lite’ lifestyle, has defined the cohort and brought with it a legacy of morbidity associated with alcohol and drug abuse among other non-communicable and communicable disease threats. As this group enters old age, it is an open question as to whether they will continue to benefit from the golden age improvements in life expectancy and quality of life that has characterised their parents’ generation.

One aspect of the dance between demographic trends, communicable and non-communicable disease patterns, and healthy life expectancy that is perhaps not widely understood and appreciated is the impact on population wellbeing and burden of disease that results from the success of scientific medicine converting life threatening to long-term conditions. The example of type 1 diabetes, a universally fatal disease before the discovery of insulin, into a long-term one with near normal life expectancy has now been extended to other forms of diabetes, to HIV/AIDS, and increasingly to cardiovascular, malignant and other system pathologies. Low-incidence problems become high prevalence and expensive ones, through the paradox of success. It is for this important reason that there is now even more of an imperative to understand and respond to the medical issues of the day through a public health prism.

The conventional framework of public health is to consider the health of the population from the point of view of primary, secondary and tertiary prevention where these terms apply to a progressive drift downstream from action on the determinants of health and disease, through screening and early identification to disease management, sometimes cure, but increasingly frequently the long-term management of an accumulation of the multiple morbidities of long-term conditions.² These could potentially consume ever-larger proportions of a nation’s wealth merely to stand still. Only by reorientation of our whole approach to health and wellbeing and to health services is there any prospect of building the good society with an emphasis on the realisation of human potential rather than on salvage. In this noble mission, clinicians have a critical part to play not only through the emphases of their clinical practice but also through their public credibility as ambassadors for healthy living and healthy public policies in all areas of life.