The real issue is inflammation. CRP goes along with inflammation, and it is inflammation that is likely to be causing heart disease.
The new study, by Dr. Paul Elliott of Imperial College in London and 35 co-authors, made use of a recently developed technique that can get answers quickly about causality. Without it, the only method was what is seen as the gold standard in medicine — large controlled clinical trials in which people are randomly assigned to take a drug, or not, and followed for years. The new method, Mendelian randomization, “is changing the way we think about causality,” Dr. Lauer said. It is a type of study that only recently became feasible as researchers found genetic variants associated with proteins like CRP and developed tools to analyze data from what was, in this case, more than 100,000 people. Different people produce different amounts of CRP, and the amount a person produces is determined by tiny inherited changes in the CRP gene. So in a population, there are people who just happen to produce more CRP throughout their lives and others who just happen to produce less. If CRP causes heart disease, those who make more CRP would have more heart disease. That, however, is not what the study found. “There was no association” between CRP genes and heart disease rates, Dr. Elliott said. People with genes that increased CRP production throughout life had no more heart disease than those with genes resulting in less CRP. The association between CRP and heart disease must be reflecting something else. For example, if CRP levels go up when heart disease begins, because there is inflammation in the arteries, CRP levels would be higher in people with incipient heart disease.
But CRP itself would be playing no role in heart disease risk — it was just marker of inflammation in the arteries. An elevated CRP level indicates increased risk, even if the protein does not cause the risk.
Bonnie - I never consider CRP a direct risk factor. It simply indicates overall inflammation, which IS a major factor in heart disease and many other inflammatory diseases.