Statins could help reduce women's risk of breast cancer.

Analysing a mammogram. High levels of cholesterol have been linked to an increased risk of breast cancer. Photograph: Rui Vieira/PA

Lowering cholesterol with statin drugs could help prevent breast cancer, research suggests.

A study of more than 600,000 British women found that the risk of breast cancer was almost doubled in those with abnormally high levels of blood fats.

The research is still at an early stage and the findings do not prove that cholesterol helps trigger breast cancer.

But if future work demonstrates a causal link it opens up the possibility of using cheap cholesterol-lowering statins to reduce women's risk of the disease.

Cardiologist Rahul Potluri, from the University of Aston, said: "We found that women with high cholesterol had a significantly greater chance of developing breast cancer.

"This was an observational study so we can't conclude that high cholesterol causes breast cancer, but the strength of this association warrants further investigation.

"A prospective study that monitors the risk of breast cancer in women with and without high cholesterol is needed to confirm what we observed. If the connection between high cholesterol and breast cancer is validated, the next step would be to see if lowering cholesterol with statins can reduce the risk of developing cancer."

A total of 664,159 women from across the UK whose health records were stored on a large database took part in the study.

Almost 23,000 (3.4%) had hyperlipidaemia, meaning their blood contained abnormally high levels of lipid fats – cholesterol and triglycerides.

Some 530 women with the condition were among the 9,312 who developed breast cancer.

Statistical analysis showed they were 1.64 times more likely to have the disease than women without hyperlipidaemia.

Previous research has shown a clear association between obesity and breast cancer in post-menopausal women.

A US study last year found that a cholesterol product called 27HC fuelled human breast tumours in genetically engineered laboratory mice.

Scientists also discovered higher levels of 27HC in both healthy breast tissue and tumour cells in women with breast cancer.

"We have a general principle that obesity is linked to breast cancer and a study in mice suggested that this may be because of cholesterol," said Dr Potluri, who presented his findings at a European Society of Cardiology meeting in Barcelona.

"We decided to investigate whether there was any association between hyperlipidaemia, which is high cholesterol essentially, and breast cancer."

He added: "While our study was preliminary, our results are promising. We found a significant association between having high cholesterol and developing breast cancer that needs to be explored in more depth.

"Caution is needed when interpreting our results because while we had a large study population, our analysis was retrospective and observational with inherent limitations. That said, the findings are exciting and further research in this field may have a big impact on patients several years down the line.

"Statins are cheap, widely available and relatively safe. We are potentially heading towards a clinical trial in 10 to 15 years to test the effect of statins on the incidence of breast cancer. If such a trial is successful, statins may have a role in the prevention of breast cancer, especially in high risk groups, such as women with high cholesterol."

Baroness Delyth Morgan, chief executive of the Breast Cancer Campaign charity, said: "These are interesting results that report a link between increased fat in the blood and an increased risk of breast cancer.

"However, this is just the first step in understanding more about how cholesterol relates to the risk of breast cancer, and more research is needed to determine whether statins could help prevent breast cancer.

"We do know that being overweight, particularly after menopause, can increase a woman's risk of developing breast cancer. We would encourage women to maintain a healthy weight and to discuss any concerns, such as their breast cancer risk, weight or cholesterol levels with their GP."