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Five interesting things … from the postcode health atlas

A new environment and health atlas unveiled last week allows you to type in a postcode and see the community-level risk for developing 14 diseases, as well as the levels of common environmental agents. Here Dr Anna Hansell of Imperial College London explains five of the most interesting ― and surprising ― findings from the atlas.

Map of hours of sunshine in England and Wales

Image copyright: Imperial College London

Map of malignant melanoma risk in England and Wales

Image copyright: Imperial College London

One of the most exciting things about the atlas is the fine scale that we’ve managed to achieve by drilling down into small area-level data (around 6,000 people per area). People have mapped disease risk and environment factors before, but never at such a fine scale. While it shouldn’t be used to see what an individual’s risk is, it does allow us to see some surprising patterns, some of which are ripe for more research …

  1. Some diseases produce ‘flat maps’. Some diseases such as lung cancer, skin cancer, liver cancer, COPD and mesothelioma showed high levels of geographical variation (high levels in some areas and low in others). But common cancers such as breast cancer and prostate cancer showed very little geographical variation ― a ‘flat map’. This suggests that environmental factors that vary between areas are unlikely to play a large role in determining the risk for prostate or breast cancer.
  2. It’s not ‘grim up north’. We didn’t find that health risks were uniformly worse in northern areas. While heart disease risks tended to be higher than average in northern compared with southern areas, breast cancer risks were lower, and lung cancer risks were higher in urban centres in both north and south of England. The health risks were adjusted for deprivation, so this shouldn’t be the explanation for our findings.
  3. Skin cancer isn’t all down to hours of sunshine. The atlas shows that malignant melanoma skin cancer risk is greatest in south west England even though sunshine duration is highest in south east England. This suggests that despite a lower level of sunlight in the south west people may be more exposed, which could trigger further research into behavioural differences between the areas.
  4. Merseyside has a significantly higher risk of liver cancer. The highest liver cancer risk was seen in the Merseyside area and this was one of the most striking geographical patterns. This might be partly related to differences in coding of this type of cancer between cancer registries across England and Wales. We also know that there’s a higher prevalence of hepatitis C infections, a risk factor for liver cancer, in Merseyside, which may also partly account for the increased risk.
  5. We really are dealing with small numbers. The print version of the atlas provides information on how many cases were seen in a census ward for each of the 14 health conditions. The rarest cancers were leukaemia, brain cancer and mesothelioma (a cancer related to past asbestos exposure). Over a 25 year period, the average number of new cases in a ward was around 14 for leukaemia, nine for brain cancer and two for mesothelioma. By comparison, breast cancer, the commonest cancer we looked at, the average number of cases was approximately 84.

We hope the atlas will not only help stimulate more research, but also provide useful information about health and the environment. We produced the atlas as a resource not just for people working in public health and public health policy but also for the general public ― we spent two years working with Sense About Science (a charity promoting better understanding of science) to help us communicate to all of these audiences. We have had over 200,000 people access the website in the first three days, which has been a phenomenal response!

Anna Hansell

The atlas was produced by the UK Small Area Health Statistics Unit (SAHSU), part of the MRC-PHE Centre for Environment and Health  based at Imperial College London. The website address is www.envhealthatlas.co.uk and a companion print volume with detailed interpretive text is published by Oxford University Press.

 

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