Public vs Private Health Decision Making
Our current CREATE V grant (www.create-center.org) has a project aimed at using technology to support health care decision making for older adults both without and with mild cognitive impairment. That project focused my attention on individual health decision making as opposed to the usual public health perspective I normally consider. That difference underlines how the same study findings could lead to vastly different “rational” choices when considering relative and absolute risk reduction.
Relative risk looks at how critical incidents (stroke, heart attack, cancer, general mortality) differ between two groups. Let’s look at statins, a drug that lowers cholesterol, a risk factor for cardiovascular disease. Say a statin clinical trial, that randomly assigns people to the drug or a placebo, follows people for 5 years and finds 100 cardiovascular events in the placebo group and 75 in the statin group, the relative risk reduction is 25% for cardiovascular events. Would you take a drug that reduces relative risk by 25%? Many clinicians leading intervention clinical trials are pleased when they find even a 5-10% reduction in relative risk.
However, as an average individual, in an individualistic society, I’m going to be less concerned with how preventing heart disease and stroke will affect y’all, and mostly with how it affects me. Here I am interested in not the relative risk reduction, but the absolute risk reduction. So, now I’ll give you a fictional example and flesh out the statistics. The size of the group in the prior relative risk example was 1000 people each in statin and control conditions. In absolute terms, your individual risk of having a negative outcome in the 5 years was 100/1000, 10%, in the placebo group, and 75/1000, 7.5 % in the statin group. Put a bit differently, you avoided a negative outcome 90% of the time with the placebo, and 92.5% of the time with the statin drug. Your absolute risk reduction was 2.5%. So, would you suffer the inconvenience and cost of taking a pill every morning for a 2.5% reduction? At least some people would say no. They might think: I’m pretty happy that I’m not going to get a negative outcome in the next 5 years (90% chance) and moving from 90% to 92.5% seems pretty small so isn’t worth the trouble. In a recent recommendation for more vigorous prescription of statins by the US Preventive Services Task force (https://www.ncbi.nlm.nih.gov/books/NBK583661/), the absolute risk reduction estimated in the review was much smaller, about 0.35% for all cause mortality, 0.39% for stroke, 0.85% for myocardial infarction (heart attack), and 1.28% for composite cardiovascular outcomes. Another statistic used to evaluate risk reduction is number needed to treat (NNT), an estimate of the number of people to whom you would need to prescribe the drug or treatment before you would find a single case of benefit: prevented one cardiovascular event such as a heart attack. The corresponding NNT estimates for the above cases were 286, 256, 118, and 78. Are you going to be the one person in a sample of 78 people to avoid the negative cardiovascular event? Or are you going to be one of the 77 people taking the drug with no benefit? Are you feeling lucky?
Now, a 1.3% absolute reduction in people suffering heart attacks and strokes would save our public and private health systems a lot of money and the cost of the prescriptions is typically low enough that there would be a net benefit to the US healthcare system. So, the public case for putting most people with elevated LDL cholesterol on statins is reasonably strong (considering the cost of the drug, side effects like increased likelihood of muscle problems and diabetes vs the cost of heart disease). The private/personal case may not be particularly strong depending on your tolerance for risk. And if we ever tried to mandate statin use, we would cause a political uproar. That is, an individualistic society appears doomed to bear higher societal health costs than a collectivist one, by putting personal freedom above collective good. So, the next time you bemoan your health care costs, which are the highest per capita in the world by a huge margin (https://www.healthsystemtracker.org/chart-collection/health-spending-u-s-compare-countries/#GDP%20per%20capita%20and%20health%20consumption%20spending%20per%20capita,%202021%20(U.S.%20dollars,%20PPP%20adjusted)), just chalk it up in part as the cost for the freedom that you and others have to offload personal health care expenditure risk on society as a whole.