After investigating 14 years of study data on over 1 million people, researchers found that women diagnosed with high cholesterol had a lower odds of developing breast cancer, compared with women without high cholesterol.
Speculating on the finding, they suggest that it shows that taking statins may protect against breast cancer and call for further research to confirm it.
The researchers, from Aston University in the United Kingdom, recently presented their findings at the European Society of Cardiology ESC Congress 2017 in Barcelona, Spain, and report in the European Heart Journal.
Breast cancer is cancer that begins when cells grow abnormally in breast tissue. Although men can also develop breast cancer, it is much more common in women.
Among women around the globe, breast cancer is the most common cancer and the fifth most common cause of cancer death. In 2012, nearly 1.7 million new cases - a quarter of all new cancer cases in women - were diagnosed worldwide.
High cholesterol and disease
The blood transports cholesterol around the body inside lipoproteins - droplets of fat covered with protein.
The researchers behind the new study also note that some studies have suggested that high blood cholesterol could be a risk for cancer.
"We previously found an association between having high cholesterol and developing breast cancer so we designed this study to follow up patients longitudinally and address the relationship more robustly," says Dr. Rahul Potluri, senior author of the study.
He and his colleagues used data from the Algorithm for Comorbidities, Associations, Length of stay and Mortality (ACALM) study. Dr. Potluri founded the ACALM Study Unit at Aston Medical School.
Lower odds of breast cancer
The study collected information from over 1 million patients attending several hospitals in the North West of England between 2000 and 2013.
The researchers pulled records from female participants aged 40 and over who were and were not diagnosed with high cholesterol at baseline (the start of the study period) and did not have breast cancer at that point.
For their analysis, the team included 16,043 women who were diagnosed with high cholesterol and an age-matched group of the same number of women without high cholesterol for comparison. The average age of the women was 66 years.
After comparing the 14 years of follow-up data on the two groups, the researchers found a lower proportion of the high-cholesterol group developed breast cancer, compared with the group that did not receive such a diagnosis at baseline (0.5 percent compared with 0.8 percent).
Further analysis revealed significantly lower odds of breast cancer in the high-cholesterol patients (odds ratio of 0.67), compared with the patients who had not received such a diagnosis.
The group that had been diagnosed with high cholesterol at baseline also had lower rates of death compared with the group that had not (13.8 percent compared with 23.7 percent).
After taking into account age, ethnicity, and other factors known to influence premature death, the researchers found that the high-cholesterol group had significantly lower odds of death (odds ratio 0.60).
The team concludes that their large, longitudinal, retrospective study shows that diagnosis of high cholesterol "has a highly protective effect on the subsequent development of breast cancer."
While they did not investigate the underlying reasons for the results, the researchers suggest that "treatment with statins or a healthier lifestyle may contribute."
They call for further studies to investigate the potential benefit of giving cancer patients medication to lower cholesterol.
"If a diagnosis of high cholesterol leads to lower breast cancer rates this must either relate to something inherent in the condition or affected patients, or more likely, to treatment with widely used cholesterol lowering interventions such as statins."
Dr. Rahul Potluri