25 October 2012
Latitude may be linked to breast cancer risk, with women living in southern regions of Australia almost twice as likely to develop the disease as women further north, research has found.
The study, conducted by the Westmead Breast Cancer Institute, Sydney, found the risk of breast cancer was nearly double for those who lived at latitudes south of 30 degrees, a line stretching from Coffs Harbour in NSW to Geraldton in WA.
Using data from state cancer registries and adjusting for age, socioeconomic status and remoteness, it found the incidence of breast cancer was about 80 cases per 100,000 for those north of 30 degrees and 160 per 100,000 for those south of 30 degrees.
Co-author Professor John Boyages, director of breast oncology at the Macquarie University Cancer Institute, said it was thought the link between latitude and breast cancer was due to the reduced potential for vitamin D synthesis from sunlight.
The study, presented at the Sydney International Breast Cancer Congress, also looked at melanoma rates and found the risk of melanoma was 35 per cent lower for those living south of 30 degrees, supporting the hypothesis that those in the south had lower sunlight exposure - which in turn leads to a reduced potential to make vitamin D.
“Four of Australia’s major mainland cities, Sydney, Melbourne, Adelaide and Perth are all below 30 degrees, so we really need to ensure women are achieving adequate vitamin D levels,” Professor Boyages said.
Senior clinical dietitian and lead author Kellie Bilinski said 2 studies had suggested women with low vitamin D had more aggressive tumours and poorer outcomes.
Ms Biliniski’s team has recruited almost 300 women for a separate study looking at vitamin D status among those newly diagnosed with breast cancer. The aim is to recruit 580 women and follow them up over 5 to 10 years to examine their vitamin D status to assess whether vitamin D deficiency is associated with a poorer prognosis.
She emphasised they were not saying low vitamin D caused breast cancer and all women had a level of risk, regardless of where they lived. They were also not recommending women just go out and supplement, she added.
“If women are concerned about their vitamin D, particularly those who live further south, then go and have it tested and if it is low then supplement,” she said.
Last Reviewed: 25 October 2012