Kabat and colleagues analysed data on 5,450 women enrolled in the Women's Health Initiative, a large multi-centre study investigating the influence of a number of factors on women's health.

Most of the women had participated in the clinical trial part of the study and provided fasting blood samples at its start (baseline) and then at years one, three and six.

The remaining women, who were enrolled in a separate 'observational' component of the study, provided fasting blood samples at baseline and at year three of the study. Among all these women, 190 cases of breast cancer were identified over eight years of follow-up.

The analysis revealed a strong association between elevated insulin levels and increased risk for breast cancer, said an Einstein release.

These findings were published in online in the International Journal of Cancer.