Under the earlier guideline statins were indicated for primary and secondary prevention based largely on LDL cholesterol levels. The new guideline, announced last year, places much less emphasis on LDL and instead places a much greater emphasis on the future risk of individuals for heart disease and stroke. The most important change is in primary prevention. Even if they have LDL cholesterol levels as low as 70 mg dl, people without established cardiovascular disease are now eligible for statin therapy if they have either diabetes or a 10-year estimated risk of CV disease of 7.5%.
There have been many attempts to quantify just how many more people are now eligible for statin therapy under the new guideline. Now in the new paper in NEJM, Michael Pencina and colleagues estimate that the new guideline results in a net increase of 12.8 million people who are now eligible for statins. Most of the newly eligible people are older adults without cardiovascular disease.
The researchers extrapolated from data from a representative sample of the US population (the National Health and Nutrition Examination Surveys, or NHANES) and calculated the number of adults 40-75 years of age who would be eligible for statin therapy under the old guideline and the new guideline:
- Under the old guideline 43.2 million adults, or 37.5% of the population, were eligible for statins.
- Under the new guideline this increases to 56 million (48.6%). Three out of 5 of the newly eligible patients would be men and their median age would be 63.4 years.
- The net increase in 12.8 million comes mostly from primary prevention– 10.4 million.
- Most of the increase occurs in older adults, between 60 and 75 years. Just under half (47.8%) of this population was eligible for statins in the earlier guideline. Now more than three-quarters (77.3%) of this age group are eligible.
- Lowering the treatment threshold to a 10-year risk starting at 5%, which the guidelines deem “reasonable,” would increase eligibility to 38.4% of adults between 40 and 60 and 87.4% of adults 60-75.
- By increasing the number of people eligible for treatment, the new guideline has increased sensitivity– that is, it will result in more people being treated who would otherwise have gone on to have a cardiovascular event– but also decreased specificity– more people will receive treatment who would not have had an event.
- The authors estimated that the increased number of people taking statins would result in 475,000 fewer events– nearly all (90%) coming from the group of older adults.
In an email interview, Allan Sniderman, one of the senior authors of the paper, said that the increase in the population eligible for treatment “has major consequences for cost and medicalization.” He agreed with other observers that the 7.5% threshold cutoff “is arbitrary.” “The way out is to better define risk. That is where we need to move forward,” he said.
An alternative to the “risk-based approach” of the new guideline, Sniderman said, is “a cause-based approach in which we identify and treat the causes in order to prevent the intramural atherosclerotic disease that will produce the clinical events.” But this approach, he acknowledged, will require more research before being adopted by future guidelines.
The NEJM paper fails to take into account the more subjective side of the new guideline, said Harlan Krumholz in an email. “The guideline recommendation is intended to be just that – a recommendation about a threshold that might make sense to use in a treatment decision. The guidelines are clear that the patient’s preference is what matters most. So it is really impossible to know if more people will be taking statins.”