The treatment paradoxBMJ 2008; 336 doi: https://doi.org/10.1136/bmj.39454.622824.94 (Published 10 January 2008) Cite this as: BMJ 2008;336:100
- Des Spence, general practitioner, Glasgow
In my shabby and stained white coat, I twirled my thick gelled fringe. He sat in a crisp, double breasted, pin striped suit, nursing a leather FiloFax and flipping through the glossy charts showing pension growth. I nodded confidently to cover my bewilderment at his sales pitch. Twenty minutes later he crushed my hand and left, with my signature on a monthly investment. Five years later I scratched my now shaven head in bewilderment at the evaluation quote of £67. I complained about mis-selling to the financial ombudsman and vowed never to be fooled or confused by an “expert” or by numbers again.
Whether it’s worth treating high cholesterol is a common enough question. No one who sees the charts and listens to the sales pitch would doubt it—but numbers are open to being spun. Let’s consider the trial known as WOSCOPS—the west of Scotland coronary prevention study (New England Journal of Medicine 1995;333:1301-8). It wasn’t by chance that the west of Scotland was chosen. The participants were men aged between 45 and 64 in the most socially deprived area in western Europe. More than three quarters (78%) were current or former smokers, and their average cholesterol concentration was 7 mmol/l. If lowering of cholesterol concentration was going to work anywhere it was going to work here. The study ran for five years, and the researchers reported a 32% reduction in cardiovascular mortality in the group of men who took statins. (Similar reductions were seen in all vascular events, but death is the irrefutable end point whose delay is most of interest to patients.) Other studies have replicated similar results, and so the pandemic of “cholesterol” swept the world.
But the numbers can be presented in another way. Converting the 32% relative risk reduction into an absolute reduction gives a derisory 0.7% reduction in cardiovascular mortality and a number needed to treat of 143 over the study period. Although it may be cheating, this figure can be annualised to give 715 to prevent one vascular death. So, putting it crudely, some 714 patients a year gain no benefit from treatment, even in the highest risk population in the world. With persistent disease creeping into younger and lower risk groups, along with a background decline in the prevalence of ischaemic heart disease, these numbers are likely to be higher.
This is the “treatment paradox”: that an individual patient, despite many years of investment in taking statins, gets virtually nil health benefit. Any relative benefit is seen only at the population level, even for composite cardiovascular end points. The treatment paradox is true of all treatable risk factors such as hypertension and osteoporosis. Patients might rightly scratch their heads and complain about mis-selling if the numbers were presented in this way. But trust me, I am no expert.