MEDIx and MEDClass

In a project funded by the NERC-led Environment and Human Health programme, we succeeded in creating two evidence-based measures capturing the health-related physical environmental characteristics of all small areas in the UK. This has never been done before, and represents a very significant contribution to the fields of environmental science, epidemiology and public health.

We took our inspiration from the ways in which multiple socio-economic deprivation is measured in the UK; via area-level multivariate indices. Such measures identify small area populations with relatively higher or lower socio-economic ‘burdens’ by combining information on residents’ characteristics such as employment status, housing status, material possessions or access to services. These multivariate measures have been successfully used in health research because i) multiple adverse socio-economic characteristics tend to be additive in their effects on health and ii) populations with similar socio-economic circumstances tend to cluster spatially. However, until recently, similar summary measures for physical environmental deprivation have not been available for the UK.

To fill this gap we first systematically identified aspects of the physical environment with good evidence of either pathogenic or salutogenic impacts for the UK population. We then sought datasets offering contemporary and complete coverage of the identified characteristics; air pollutants (PM10, NO2, SO2, CO), climate, proximity to waste management or metal production/processing sites, drinking water quality, noise levels, exposure to UVB radiation and quantity of green space in the neighbourhood. Data on noise and drinking water quality were not available for the whole UK and these characteristics were excluded.

We combined the data sets into two different indicators: the Multiple Environmental Deprivation Index (MEDIx) is an ordered measure which represents the balance of pathogenic and salutogenic characteristics in a ward; the Multiple Environmental Deprivation Classification (MEDClass) classifies areas into one of 7 types, based on the combination of environmental characteristics present. Both indicators are at CAS ward level.

Why did we do this? Higher levels of socio-economic deprivation are associated with worse health in almost all societies. In the UK, socio-economic inequalities in mortality persist and continue to widen, despite considerable policy attention. There are several competing explanations for the mechanisms by which socio-economic inequalities in health occur. One theory is that socio-economic deprivation raises the risk of exposure to adverse physical environments which may be pathogenic, or reduces exposure to physical environments which may be salutogenic. There are numerous aetiological pathways via which low socio-economic position, and behaviours associated with it, might damage health. Similarly, there are many pathways via which an adverse physical environment might damage health. The sometimes close association between socio-economic and environmental deprivation thus means that it can be hard to separate out their relative contributions to health inequality; are those exposed to an adverse physical environment at greater risk of poor health because of their environmental circumstances? Or is the greater risk simply a function of their relative socio-economic deprivation, which also happens to place or keep them in less pleasant environmental circumstances?

In our research, we have used these indicators to demonstrate that exposure to multiple physical environmental deprivation is related to socioeconomic deprivation, that multiple physical environmental deprivation is independently related to risk of all-cause and cause-specific mortality and morbidity, and that unequal exposure to physical environmental deprivation explains a significant portion of socio-economic inequalities in health in the UK.

You can read more about this work in the following publications:

Pearce J, Richardson EA, Mitchell R, Shortt NK. (2010) Environmental justice and health: the implications of the socio-spatial distribution of multiple environmental deprivation for health inequalities in the United Kingdom. Transactions of the Institute of British Geographers.

Richardson EA, Mitchell R, Shortt N, Pearce J, Dawson T (2009) Evidence-based selection of environmental factors and datasets for measuring multiple environmental deprivation in epidemiological research. Environmental Health; 8 (Suppl1): S18.

Richardson EA, Mitchell R, Shortt NK, Pearce J, Dawson TP (2010) Developing summary measures of health-related multiple physical environmental deprivation for epidemiological research. Environment and Planning A.

Shortt NK, Richardson EA, Mitchell R, Pearce J. (2010) Re-engaging with the physical environment: a health-related environmental classification of the UK. Area.

You can download MEDIx and MEDClass from here

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