The Poor Design of Online Heart Risk Calculators

A few days ago the Washington Post published an article criticizing the reliability of online heart risk calculators. But the article failed to discuss the main reasons why such calculators are poorly designed. Let's look at some of the reasons why the average heart risk calculator is likely to do a poor job of alerting you if you have a relatively high risk of a heart attack over the next ten years.

Reason #1: The calculators ask for inputs on current cholesterol levels rather than asking about your lifetime eating habits.

All of about 8 or 9 online heart risk calculators I've looked at ask for your current total cholesterol level and the level of your HDL or “good” cholesterol. There are some big problems with doing that. The first is that a large fraction of all people don't remember what their latest HDL reading was. If you are like most people over 50, you probably remember whether your latest cholesterol reading was above 200, but don't remember what your HDL reading was. In such a case you will be unable to proceed when you come to a calculator such as the calculator here.

Another problem is that your latest cholesterol reading may not be a very good indicator of your current eating habits. Many people alter their eating habits in the weeks before taking a scheduled blood test, in hopes of getting a better cholesterol reading.

A third reason is that your heart attack risk depends relatively little on your current cholesterol level, and more on your lifetime eating habits. A heart attack can occur when plaque builds up in your arteries. The likelihood of that happening depends on your eating habits over the past few decades. Let's imagine two people, Ed and Sam, both age 60. Ed has been eating tons of red meat for four decades, but in the past year has reformed his eating habits, and brought his total cholesterol down to 200. Sam for the past 40 years has been eating little food high in bad cholesterol, and lots of food high in good cholesterol. But in the past year he's slipped a little, and his total cholesterol is now 220. Which has a higher chance of heart attack? It's Ed, not Sam, despite Ed's current lower cholesterol – because your lifetime eating habits determines how much plaque is in your arteries.

It would seem that rather than asking about your latest cholesterol reading (requiring an HDL number you probably don't know), our heart risk calculators should instead be asking about your lifetime eating habits.

Reason #2: None of the calculators has an input for resting heart rate.

There have been many scientific studies indicating that a person's resting heart rate has a large effect on a person's chance of having a heart attack or suffering sudden cardiac death. In the large Framingham heart study, the average resting heart rate for a male was 64 beats per minute. A much larger FitBit data set (derived from millions of users of FitBit devices) suggests that the average heart rate for male 60-year-olds in the US was about 62 beats per minute. But what if your resting heart rate is 70 beats per minutes or 80 beats per minute or 87 beats per minutes? According to numerous studies such as this one, your risk of heart failure or sudden cardiac death is much higher – perhaps as much as 300% higher for someone with a heart rate greater than 85 beats per minute.

Given the significance of heart rate, and the ease in which anyone can get their own resting heart rate by holding their wrist and using a clock, there would seem to be no excuse for not having a heart rate input slot on every online heart risk calculator. But how many such calculators have such a thing? None of them do.

Reason #3: Most of the calculators don't allow you to specify whether you have a family history of heart disease.

Most of the online risk calculators use what is called the ASCVD algorithm, and such calculators do not ask you whether you have any family history of heart disease. For example, the first calculator I get when I do a Google search for “heart risk calculator” is a calculator that does not ask me for whether anyone in my family had a heart attack.

But there is one online heart risk calculator that uses the “Reynolds risk” formula for computing heart risk, and that calculator does ask me “Did your mother or father have a heart attack before age 60?” When I choose “Yes,” my calculated 10-year heart attack or stroke risk jumps from 8% to 13%. So evidently whether your father or mother had a heart attack before 60 is a big factor that can affect your heart risk by as much as 40%. So why do the vast majority of online heart risk calculators not allow you to specify whether your mother or father had a heart attack before the age of 60?

Reason #4: None of the calculators allow you to specify whether you have a diagonal earlobe crease.

A diagonal earlobe crease is a line that some people have going across their earlobes. It looks like this:

Quite a few scientific studies have shown that if you have a diagonal earlobe crease on both ears (called a “bilateral” earlobe crease), the chance of you having cardiovascular disease is much higher. For example, this 1982 study was based on exact measurements of the artery health of 340 people, using coronary arteriography. The study found that having a diagonal earlobe crease has a positive predictive value of 91% for coronary artery disease, meaning if you have the diagonal earlobe crease you are 91% likely to have coronary artery disease. A similar 2004 study of 415 people (also using exact artery measurements though angiography) found that having the diagonal earlobe crease had a positive predictive value of 89% for coronary artery disease.

Clearly all of our heart attack risk calculators should have an input allowing you to specify whether you have an earlobe crease. But none of these calculators has such an input.

Reason #5: None of the calculators has an input asking about your exercise levels.

How much a person exercises can affect his risk of having a heart attack. It will come as little surprise that not exercising at all will increase your risk of a heart attack. But what is surprising is that a major study found that those who exercise very heavily may have a much higher risk of heart attack. Such is the finding of the very large CARDIA study. The Science Daily site reports this finding with the headline, “Physically active white men at high risk for plaque buildup in arteries.” The site states, “White men who exercise at high levels are 86 percent more likely than people who exercise at low levels to experience a buildup of plaque in the heart arteries by middle age, a new study suggests.”

Clearly, a decent heart attack risk calculator should have an input for how much you exercise. But none of the online calculators has such a thing.

Reason #6: None of the calculators has an input asking about how much time you spend sitting. 

It is sometimes said, "Sitting is the new smoking," because too much sitting can cause an increased chance of heart attack.  A 2015 meta-analysis on the association between heart risk and sitting found an association, but a pretty modest one, with a hazard ratio of 1.143, meaning lots of sitting might cause a 14% higher chance of a heart attack.   But a 2012 meta-analysis found a much larger risk, finding that those who sit the most can have "a 147% increase in the RR [relative risk] of cardiovascular events." Clearly a question on how long you spend sitting each day should be included in a heart risk calculator. None of them currently has such a thing. 

Reason #7: None of the calculators has an input asking about how much time you spend standing at work. 

Given the information just discussed, you will be surprised to read the following quotes from a scientist who summarizes a large study done by he and his colleagues:

We found that people who primarily stand on the job are twice as likely to develop heart disease as people who primarily sit....In fact, the incidence of heart disease among those respondents who stood a lot at work (6.6 per cent) was similar to the incidence of heart disease among workers who smoked on a daily basis (5.8 per cent) or those who were obese (6.9 per cent). 

What a decent heart attack risk calculator would look like

Based on all these considerations, I can show what a good heart attack risk calculator would look like. It would look like the page below, a page looking very different from all existing heart attack risk calculators. Unfortunately I can give you no URL for a page that implements such a design. I hope someone with expertise in this field will one day implement such a calculator.