Study sheds light on who is most at risk of skin cancer in Ireland
A study into the most common types of skin cancer has found striking risk factors associated with where people live and how rich or poor they are, according to new research in the British Journal of Dermatology.
The study, released online today, examined incidence rates in Ireland for the two commonest types of skin cancer, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), over a ten-year period.* The researchers looked specifically at two issues: the geographical locations where these cancers are most common, and the socioeconomic status of the patients.
People living in cities were found to have a far higher risk of developing BCC, the most common type of cancer, with women a massive 48 per cent and men 35 per cent more likely to develop the disease in the most urban compared to rural areas.
However for the other type of skin cancer studied, SCC, while this again affected women more in urban areas, the situation for men was very different, with risk almost 10 per cent higher in the areas with the highest, compared to the lowest, percentage of farmers (i.e. rural rather than urban areas.)
Risk by location
Looking at all non-melanoma skin cancers (BCC and SCC combined), incidence was higher than average along the coast, particularly in three spots along the west coast (Kerry in the south, Mayo in the mid-west and Donegal further north), and in and around the two main cities, Dublin and Cork. The geographical distribution was similar in men and women, although higher rates were found in rural areas in men than in women.
However, when BCC and SCC were considered separately, very different geographical patterns became apparent. While the coastal and city areas proved to have the highest incidence rates for both SCC and BCC, interestingly, BCC seemed especially prevalent in cities and SCC in coastal areas.
The highest rates of BCC were concentrated in urban areas like Dublin, Cork, Galway and Waterford and a few coastal areas in the south and west of the country. The distribution was similar in males and females. For SCC, in contrast, higher risks were seen more commonly on the coasts (on the south, mid and north-west coast) and in the north-east, and risk was raised only in parts of Dublin, rather than throughout the city.
People living in the most densely populated areas were far more likely to develop a BCC – men in the most urban areas were found to have a 35 per cent and women a 48 per cent higher risk, compared to people in rural areas.
Interestingly, while the areas of highest risk were the same for men and women for BCC, they were very different between the sexes for SCC, which affected women most in the cities and men most in rural and farming communities, especially in the south-west.
Who was most affected
BCC risk in men and women was significantly higher in more affluent people (those living in the least deprived areas). In fact, for both sexes, people living in the most deprived areas had a 14 per cent lower risk of being diagnosed with BCC than those in the least deprived areas.
The same principle was true for SCC in men (it was more likely to affect more affluent men) but interestingly not for women.
For women, geographical location seemed to be a greater risk factor than socio-economic status, with risk of both BCC and SCC higher for women in the most densely populated areas (cities).
What the findings mean
Solar radiation is the major non-melanoma skin cancer risk factor. However, in Ireland, sun exposure is highest in the south-east of the country, where the rates of skin cancer were low. Moreover, differences in sunshine across the country are rather small (only one daily hour difference between the lowest and highest levels). Therefore, levels of sun in the different geographical areas are unlikely to account for the differing risk rates. Likewise, differences in people’s skin types do not vary greatly enough across the country to account for the variations.
Exposure to UV radiation would be expected to be higher in areas with high proportion of outdoor workers (e.g. in agriculture, fishing, construction). Higher risks (particularly of SCC, for which occupational UV exposure appears to be most impactful) were found in coastal areas where workers from the fishing industry may have been more exposed to UV as may some farmers working close the sea.
Another possible explanation is that the least deprived individuals (who are shown to have increased risk) tend to move out from cities to more pleasant coastal locations later in life, therefore increasing incidence in those areas. This would especially have an impact on BCC risk, since these cancers are associated with burning and intermittent UV exposure (such as you might get from a beach holiday) rather than more long-term, cumulative exposure (such as you might get from working outdoors.)
Geographical differences in the intensity of detection of skin cancer may also explain the findings. A 2003 national report** showed large variation in distribution of dermatologists across the country. In particular, a lack of dermatologists in the Midlands and North-Western health boards was identified. This lack of dermatologists could result in cases of skin cancers going undiagnosed in these areas.
Linda Sharp of the National Cancer Registry and one of the study’s authors said: “BCC in both sexes and SCC in females were more common in residents of more densely populated areas. Since BCC is mostly non-fatal, these differences may partly reflect variations in awareness and use of cancer services. In Ireland, rural residents have the lowest access to GP services. In addition, studies show that individuals with the lowest incomes are significantly less likely to be referred to a specialist. It is possible that people living in urban or less-deprived areas may be more aware of the risks of UV exposure and therefore more likely to report potential skin lesions to their GP.”
Another possibility is that more affluent people may be more likely to take foreign holidays, while those in urban areas are likely to have better access to airports for holidays abroad and businesses offering tanning facilities. In Ireland, census data shows that Dublin residents are much more likely to travel abroad than those from elsewhere. Moreover, the percentage who had used sunbeds in 2007 was higher in urban than rural areas (9% vs 4%) and in those of higher social class. In addition, the likelihood of people protecting themselves from skin cancer may differ in urban and rural areas and by socioeconomic status.
Nina Goad of the British Association of Dermatologists said: “This study provides a fascinating insight into who is most likely to be diagnosed with skin cancer, our most common cancer. One very interesting hypothesis for the variations we are seeing in different areas and different levels of wealth, relates to diagnosis of skin cancers. If the striking variations in risk factors that this study reveals are in some part down to the fact that people in rural locations and people in more deprived areas are less likely to see their GP with a possible skin cancer, or are less likely to have their lesion diagnosed by a dermatologist, then this shows that we have a lot of work to do to address these issues and to try to raise the profile of self-check messages among these groups.”
Collectively, BCC and SCC are called non-melanoma skin cancer and are the UK’s most common cancer, with over 70,000 new cases diagnosed across the UK annually, 5,000 of which are in Ireland. However, as data collection for these cancers is poor, the actual figure is thought to be much higher, with an estimated actual figure of 100,000 new cases every year across the UK.
Ultraviolet (UV) exposure from the sun or sunbeds is thought to be responsible for the vast majority of skin cancers, but UV plays a different role on BCC and SCC.
SCC is largely associated with occupational sun exposure, for example people who work outdoors and have cumulative sun damage, while BCC is more strongly associated with intermittent sun exposure and sunburn, such as from beach holidays, and especially early in life. Both types are more common in paler skinned people.
Previous studies into melanoma, the most deadly but least common type of skin cancer, have found that it is more common in more affluent people, and this has been attributed in part to increased foreign travel in these groups. However, this is the first UK study to look at the more common non-melanoma skin cancers.
Ireland is an ideal location for such a study as non-melanoma incidence rates are high by international standards, and data collection is more uniform in one location as opposed to a country-to-country comparison. Additionally, skin types and UV levels are similar across the country, meaning these risk factors are constant and will not lead to significant inconsistencies of results in different geographical locations (i.e. where one area has been shown to have higher rates of BCC, it is unlikely to be because people in this area are paler skinned or that it is sunnier than elsewhere in Ireland.)
*47,347 cases diagnosed 1994-2003. 14,236 had SCC and 32,226 had BCC.
** Comhairle na nOspidéal. Report of the Committee on Dermatology Services –
November 2003. Available at www.comh-n-osp.ie
Notes to editors:
1. If using this information, please ensure you mention that the study is being released in the British Journal of Dermatology, the official publication of the British Association of Dermatologists
2. For more information please contact: Nina Goad, British Association of Dermatologists, Phone: 0207 391 6355, Email: email@example.com, Website: www.bad.org.uk
3. Articles in the BJD can be viewed online: www.brjdermatol.org
British Journal of Dermatology: Geographical, urban/rural and socio-economic variations in nonmelanoma skin cancer incidence: a population-based study in Ireland. A.E. Carsin,*†‡ L. Sharp* and H. Comber*
*National Cancer Registry Ireland, Kinsale Road, Cork, Ireland
†Centre for Research in Environmental Epidemiology (CREAL), C. Dr Aiguader, 88, 08003 Barcelona, Spain
‡Municipal Institute of Medical Research (IMIM-Hospital del Mar), Barcelona, Spain
Accepted for publication, 22 November 2010.
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