Association between breast cancer incidence and latitude in mainland Australian women

Kellie Bilinski, John Boyages, Karen Byth

    Research output: Contribution to journalMeeting abstract

    Abstract

    Aim: Higher rates of breast cancer at latitudes further from the equator in comparison to latitudes close to the equator have been shown in several international ecologic studies. Our aim was to investigate the association between breast cancer and latitude in Australia.

    Methods: Female breast cancer incidence by five-year age group between 2002 and 2006 were obtained for all mainland Australian Local Government Areas (LGA). Latitude, Accessibility/Remoteness Index of Australia (ARIA) and Index of Relative Socioeconomic Disadvantage (IRSD) were assigned to each LGA. Data were aggregated into five latitude bands (≤27; >27–30; >30–33; >33–36; >36°S). We estimated the Odds of breast cancer by fitting univariate, bivariable and multivariable logistic regression models with breast cancer as the response variable adjusting for latitude, age-group, IRSD and ARIA. The analysis was replicated with melanoma as the response variable to support the hypothesis that increasing latitude is associated with decreasing sun exposure.

    Results: In women aged 20–89 years, the Odds of breast cancer at latitude south of 27°S was 2.1 to 2.4 times higher than at latitude ≤27°S (univariate model, p < 0.001). In bivariable analysis, age adjusted Odds of breast cancer also increased with increasing latitude for each category of IRSD and remoteness (OR 1.1–2.9, p ≤ 0.001). In multivariable analysis, the Odds of breast cancer was 1.22 (1.17–1.26) at latitudes >27–30 and 2.12 (2.04–2.2) to 2.37 (2.28–2.47) at latitudes >30 (all p < 0.001). Conversely, in the same population, after adjusting for age-group, IRSD and ARIA the Odds of melanoma was 0.62 (0.58–0.63, p < 0.001) at latitudes >36°S compared to latitude ≤27°S (p < 0.001).

    Conclusions: We report a significant relationship between latitude and breast cancer incidence in Australian women which supports international findings showing an ecological gradient for breast cancer. Although we are cannot infer causality, these findings support suggestions that higher vitamin D concentrations associated with increased sunlight exposure is associated with reduced risk of breast cancer.
    Original languageEnglish
    Article number757
    Pages (from-to)318
    Number of pages1
    JournalAsia-Pacific Journal of Clinical Oncology
    Volume8
    Issue numberSupplement 3
    DOIs
    Publication statusPublished - Nov 2012
    EventJoint Meeting of the COSA 39 Annual Scientific Meeting and IPOS 14 World Congress of Psycho–Oncology - Brisbane, Australia
    Duration: 13 Nov 201215 Nov 2012

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