Millions now take statins to protect their heart
Slow blood flow in areas of the body's arteries may reduce the protective effect of statins, research suggests.
The study suggests sluggish blood flow tends to hinder statins' ability to trigger production of beneficial antioxidant molecules.
The body's own protective mechanisms also tend to fail in the same areas - leaving them vulnerable to damage.
The Imperial College London study is featured in the Journal of Biological Chemistry.
It raises hopes of new ways to improve general artery health.
Statins are estimated to save nearly 10,000 lives a year in England alone by cutting the risk of cardiovascular disease.
Their primary action is to lower levels of harmful LDL cholesterol which can clog up the arteries.
However, they are also thought to stimulate production of beneficial antioxidants in the cells of the arteries by boosting levels of a key enzyme, called heme oxygenase (HO-1).
The Imperial team investigated the antioxidant potency of statins in different parts of the circulation by measuring the amount of HO-1 in the endothelial cells that line the arteries.
They found the increase in HO-1 induced by the statin was significantly higher in cells exposed to fast and regular blood flow than in cells where blood flow was sluggish or disrupted.
Previous research has shown endothelial cells produce protective biological signals in parts of the artery where blood flow is fast to counter the build up of fatty cholesterol deposits.
But the cells do not react in the same way in areas where blood flow is sluggish.
The latest study reveals that statins fail to work well in exactly the same areas where the body's natural defences are weak.
Researcher Dr Justin Mason said: "Arteries don't clog up in a uniform way.
"Bends and branches of blood vessels - where blood flow is disrupted and can be sluggish - are much more prone to fatty plaques building-up and blocking the artery.
"What we have shown is that those regions of the arteries most likely to become diseased are the same regions that may not be benefiting maximally from statin treatment - a double whammy."
The research team hopes to find other ways to get the most out of statins, or to find other ways to switch on protective mechanisms in vulnerable areas of arteries.
Dr Faisal Ali, who also worked on the study, said: "We wanted to model blood flow because cells lining our veins and arteries are constantly exposed to the flow of blood.
"This alters their behaviour, how they respond, both to natural signals and to the drugs that we will take at one time or another."
Professor Peter Weissberg, medical director of the British Heart Foundation, which funded the study, said: "This research demonstrates how the physical forces inside blood vessels may influence the local action of drugs such as statins.
"The findings open avenues of investigation that could lead to greater health benefits of statins' being realised."