Does city life cause breast cancer?

Women living in the city have denser breast tissue which can increase cancer risk, reports Sanjay Tanday.

What is the story?
Women living and working in the city have a higher risk of developing breast cancer than women in suburban and rural areas, media reports claim.

UK researchers discovered that women from urban settings were twice as likely to have dense breast tissue, which increases their risk of developing tumours.

Previous research showed that women with more glandular tissue in their breasts are up to four times more likely to develop breast cancer than women with breasts consisting mainly of fat.

What is the research?
The reports are based on research presented last month at the annual conference of the Radiological Society of North America in Chicago.

For the study, the researchers analysed digital mammograms of 617 women, aged 29 to 87, who underwent mammography at the London Breast Institute.

Of these women, 225 lived in the countryside, 135 in suburban areas and 257 in urban areas.

Association between breast tissue density and area of residence was assessed using logistic regression analysis to calculate age-adjusted relative risk.

This showed all women living in urban areas had a 32 per cent increased risk of breast cancer, compared with women from rural areas.

The risk was doubled among those aged 45 to 54.

These women were also twice as likely to have at least 25 per cent of their breasts made of dense tissue as those from the countryside.

Overall, 26 per cent of mammograms were classed as entirely fatty, 30 per cent as having scattered fibroglandular densities, 22 per cent as dense and the remaining 22 per cent classed as extremely dense

Breast density decreased in line with distance from the urban centre, becoming progressively less pronounced in suburban and rural areas.

What do researchers say?
Professor Kefah Mokbel, consultant surgeon at the London Breast Institute, who was involved in the study, said: 'We propose that the modest increase in breast cancer risk seen in women from cities may be down to the higher levels of traffic and air pollution found in urban areas.

'Traffic emissions contain polycyclic aromatic hydrocarbons which mimic the effects of oestrogen and disrupt the make up of the breasts.'

Dr Nicholas Perry, director of The London Breast Institute in London, said that the study findings showed that regular access to breast screening for women living in cities should be made a priority.

'Currently, women who live in urban areas are known to have lower attendance for breast screening programmes than women in outlying areas,' he explained.

All women should maintain a recommended breast-screening regimen, and women with dense breasts be screened using digital mammography, which is more effective at detecting cancer in dense breast tissue, Dr Perry added.

What other researchers say?
Dr Alexis Willett, policy manager at the charity Breakthrough Breast Cancer, said: 'Although breast density is known to affect breast cancer risk, more research is needed to understand how.

'Breast cancer is a complex disease and its causes are unknown for the majority of the 44,000 women diagnosed each year in the UK.

We do know that for most women age is the biggest risk factor for breast cancer, which is why we encourage all women over 50 to attend NHS breast screening, added Dr Willett.

Annual conference of the Radiological Society of North America 2007.

Informing patients

  • Women living in cities have a higher risk of developing breast cancer than women from the suburbs.
  • Women from urban areas were twice as likely as those in rural areas to have dense breast tissue.
  • Further research is required to identify the exact cause of the link.
  • GPs should advise women living in urban areas to go for regular breast-screening.
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