For example, one protein found in blood – C-reactive protein (CRP) – is associated with an increased risk of cardiovascular disease, so some researchers have suggested that drug companies should search for drugs to reduce CRP levels. But epidemiologists in Bristol have questioned whether such treatments would be beneficial. Because CRP is influenced by lifestyle factors such as smoking, diet and exercise, it is impossible to tell whether CRP causes cardiovascular disease, or whether these other risk factors are the real culprits. If CRP is not a cause of cardiovascular disease, then treat-ments to lower it will not be beneficial.

Bristol’s epidemiologists have developed a novel approach to sorting out the wood from the trees. Because CRP is a protein, it is encoded by genes. The fact that genes are fixed before birth and randomly allocated can therefore be exploited.

Some people have genes that cause naturally high levels of CRP, while others have low or medium levels, but the proportion of people who smoke, take no exercise or have a bad diet will be similar in each of these genetic groups. Using this technique, researchers have shown that CRP is not causally related to high blood pressure. These important results thus allow the search for the real culprit to continue.

The Bristol Heart Institute