Breast cancer in Maori and non-Maori women

Background Breast cancer is more common in Maori than in non-Maori women un der the age of 40 years and is equally common in older women, despite Maori being generally of lower socioeconomic status and having had a higher fert ility rate than non-Maori. Methods Data from a nationwide population-based case-control study of breas t cancer in New Zealand women aged 25-54 years were used to compare the age -adjusted distribution of reproductive and other risk factors for breast ca ncer in self-identified Maori and non-Maori women from the control group. S eparate analyses also were carried out for women aged 25-39 years and for t hose aged 40-54 years. The risk of breast cancer according to the proportio n of Maori ancestry was estimated using multiple logistic regression simult aneously adjusting for several risk factors. Results Significant differences were found between self-identified Maori an d non-Maori women in the age-adjusted frequencies for education level, soci oeconomic status, age at first full-term pregnancy, parity, and duration of breastfeeding; the profile in all instances suggesting a lower risk of bre ast cancer for Maori than for non-Maori. There were no significant differen ces with respect to age at menarche, surgery for benign breast disease or a family history of breast cancer. Significantly more Maori than non-Maori w ere in the highest quartile of recent body mass index. Women self-identifie d as Maori has an approximately twofold higher risk of breast cancer than n on-Maori women. Conclusions Maori have high rates of breast cancer despite having a more fa vourable profile than non-Maori for most identified risk factors.