A new study has linked the type of diabetes treatment with breast density, a strong risk factor for breast cancer. Diabetes controlled by diet or pills appears to reduce breast density, whereas using insulin might increase it.

Latest research finds diabetes treated by insulin might increase breast density

The prospective study referenced above was designed to determine whether diabetes and diabetes treatments are associated with breast density. High mammographic breast density is a strong breast cancer risk factor. The few studies that have examined the potential link between diabetes and breast density have found no or weak associations. However, none of these studies took into account the type of diabetes treatment.

The study included 5,703 Danish women over the age of 50 (average age 56), of whom 4,501 were postmenopausal. The women were enrolled in the Danish Diet, Cancer and Health cohort during the period 1993 to 1997 and subsequently underwent regular breast cancer screening mammograms. Diabetes status and treatments (diet, pills or insulin) were reported by participants upon enrollment. The authors used the baseline breast density from the first mammogram after enrollment in the analysis. Mammographic breast density was categorized as either mixed/dense or fatty (i.e., non-dense). A total of 137 (2.4%) of the women had diabetes and 3,212 (56.3%) had mixed/dense breasts.

Women with diabetes were less likely overall to have mixed/dense breasts. This inverse association held after adjusting for obesity and other relevant factors. When the treatments used by the diabetic women were considered, similar inverse associations were found for the 44 women who controlled their diabetes with diet alone and the 62 who took oral medications such as metformin (but no insulin). On the other hand, the 31 women using insulin had double the likelihood of mixed/dense breasts, however this result was no statistically significant. The authors conclude that having diabetes controlled by diet or pills decreases breast density, whereas taking insulin might increase it.

Please see our articles on type 2 diabetes and breast density for more information.