Cholesterol medication, pictured, aims to lower bad cholesterol levels and raise good cholesterol. However, high levels of "good cholesterol" do not protect against heart attack, according to a new study.

A 14-year study involving more than one million women has found that those with high cholesterol have strikingly lower rates of breast cancer and improved mortality, a phenomenon the researchers have linked to the use of statins. Many people take the drug to lower their cholesterol.

"Showing that patients with high cholesterol have a lower risk of developing breast cancer and subsequent mortality in a longitudinal study like this provides the strongest evidence for a protective effect, which is likely related to statins", said Dr Rahul Potluri, a senior author of the study which took place at Aston Medical School, Birmingham, UK.

The link between high cholesterol and breast cancer has been "fascinating researchers for the last few years", he added.

Dr. Paul Carter, lead author of the study, added: "Our research confirms that women with a diagnosis of high cholesterol have strikingly lower rates of breast cancer with improved death rates and survival.

"The results of this study provide the strongest justification to date for a clinical trial evaluating the protective effect of statins in patients with breast cancer, and this is what we intend to do.

"I don't think at the moment we can give statins to prevent or reduce mortality from breast cancer per se. But a positive result in a clinical trial could change this and it is an exciting and rapidly progressing field."

The study examined 1,220,024 women over the age of 40 between the years 2000 and 2013. They looked at patients who had been diagnosed with high cholesterol and those with lower levels to gauge the occurrence of breast cancer in the two groups as well as the resulting mortality rates.

After adjusting for factors which may affect mortality – such as, sex, age and ethnicity - the team found that the women with high cholesterol were 45% likely to develop breast cancer than those without. Furthermore, those with high cholesterol that did develop the disease were 40% less likely to die than those with lower levels of cholesterol.

Dr Potluri added: "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."