The thing with maps…
By Professor Tony Arthur
What is it with maps? There is nothing as powerful as a map to demonstrate at a glance how social, demographic, health, and political factors are distributed within and between different regions of the country. In Britain, the effect is perhaps even more striking, an island allowing us to compare not only differences between north and south, urban and rural, but coastal and inland too. In the immediate aftermath of a general election we scan over maps to see how those concentrated clusters of red in cities and the north have shrunk or expanded against a broader sea of blue to discover where historical allegiances survived and political arguments resonated. And our eyes usually flit to ‘home’ or places important to us to see how we compare with the broader picture (for me that’s right at the bottom, the Isle of Wight where I grew up, just discernible as a land apart).
Most diseases or health needs are strongly associated with demographic factors. This means that there are often great geographical differences in how the health of the nation is experienced. Ideally, the provision of health services should reflect these differences but how services evolve and develop is not determined by need alone. The Inverse Care Law, first proposed in 1971 by Julian Tudor Hart and underpinning arguments for greater equity in service provision ever since, goes much further suggesting that the greater the population need for healthcare the worse the provision. The National Institute of Clinical Excellence was created nearly 20 years ago to address the problem known as ‘postcode prescribing’ whereby an individual’s access to certain treatments was dependent on the locality within which he or she lived. But if you like maps then head over to the NHS Atlas of Variation where you can see not only how cancer mortality, circulatory disease, and childhood obesity vary across the country but also how services like critical care and mental health provision are distributed.
As part of the remit of the DEMCOM study, an evaluation of dementia friendly communities, we are attempting to map the provision of these community initiatives and see how this relates (or doesn’t) to epidemiology-based need. In doing so, several questions must be considered relating to both the ‘need’ and ‘provision’ side of the equation. Estimates of the prevalence of dementia are drawn from the second Cognitive Function and Ageing Study (CFAS II) and have been applied to individual CCG populations. There are at least three ways to plot need in each CCG area: (1) known cases of dementia; (2) estimated point prevalence of dementia (percentage); and (3) estimated number of cases based on the size and make-up of the local population. Another question to be addressed is how to categorise need. Quartiles or quintiles are intuitive but give an indication of relative rather than absolute need and suggest variation even when that may be negligible. For purists, pre-determined categories may more accurately reflect variability but relative differences may be lost. Mapping provision raises other, possibly greater, challenges. A dementia friendly community is, like any ‘community’, not always likely to have an obvious centre to be pinpointed nor clearly defined boundaries. As we move to the next phase of the DEMCOM study where we are undertaking case studies of specific dementia friendly communities we will build a more in-depth understanding to complement the broad brush picture that mapping can provide.
Are health maps helpful? Yes, but they are seductive too and open to a host of interpretations. To avoid getting lost, the key to map reading is in the legend. Read the small print.
Please see here for more information on the DEMCOM project