Black women are more likely to die from breast cancer compared to white women, and one major reason is health insurance disparities, writes the American Cancer Society.

Previous research has shown that since the early 1980s, black women have been more likely to die from breast cancer than white women. Data from 2015 showed a 39% higher breast cancer death rate in black women.

To find out why these differences occur, the authors of the new study analyzed data from more than 550,000 nonelderly women with breast cancer (ages 18 to 64). They studied 5 factors and found that differences in health insurance seemed to make the most significant contribution.