Population attributable risks for modifiable lifestyle factors and breast cancer in New Zealand women

Abstract

Breast cancer is the most commonly diagnosed invasive cancer in New Zealand women and modifiable lifestyle risk factors may contribute to this. To estimate population attributable risks for modifiable lifestyle factors and breast cancer in New Zealand. Estimates of the magnitude of the impact of modifiable lifestyle risk factors for breast cancer (relative risks and odds ratios obtained from published epidemiological studies) and the prevalence of exposure in New Zealand were used to calculate the population attributable risk percent (PAR%) for each risk factor. The PAR% show the relative importance of these considered risk factors and give an indication of the potential impact of reducing the prevalence of these lifestyle risk factors on the incidence of breast cancer in New Zealand. Six modifiable lifestyle factors were identified for breast cancer. These were obesity, lack of physical activity, high alcohol intake, oral contraceptive use, hormone replacement therapy (HRT) and delayed first birth. The PAR% for these risk factors ranged from 1% for delayed first birth to 10% for obesity (16% for Maori women and 17% for Pacific women). The most important primary preventive strategies to reduce the risk of breast cancer in New Zealand are lifestyle changes to reduce obesity, promoting regular physical activity (which may in turn reduce the prevalence of obesity), reducing HRT use and avoiding high alcohol intake. Strategies that encourage regular physical activity and reduce obesity could also have other benefits, such as reduced risks of cardiovascular disease and diabetes.