Are You Five For Five?

I have recently gotten in the habit of asking my fellow medical residents and patients what percentage of heart attacks they estimate are preventable. That is, with our current understanding of the causes of coronary heart disease, what proportion of heart attacks can be prevented. Most of my colleagues estimate that 40 to 60 percent of heart attacks can prevented. “About half,” is the most common response I get. They often cite the benefits of statins and antihypertensive medications as well as advances in cardiac catherization to explain their estimate. Those heart attacks that aren’t preventable result from limitations in our understanding of atherosclerosis or conditions we can’t change such as genetic predisposition. My patients’ estimates range from 30 to 75 percent. Patients are more likely to cite advances in technology such as CT scanners and drug eluting stents to explain our ability to prevent heart attacks. As for heart attacks that aren’t preventable, to quote one of my patients, “Sometimes bad stuff just happens, that’s all.”

The truth is that heart attacks rarely occur in the absence of established risk factors. Studies show that 90 to 95 percent of heart attacks occur in people with one or more risk factors. What’s more is that simply controlling 5 risk factors for coronary heart disease nearly eliminates your risk of heart attacks.* This suggests that heart attacks are almost completely preventable.** Yes, there are inexplicable cases of coronary heart disease, but these are rare.  Far more common are heart attacks that occur in the setting of these 5 risk factors, all of which are preventable or treatable.

So what are these 5 risk factors? What are the 5 protective factors that can nearly eliminate your risk of heart attacks?***

1. Not smoking

2. Blood pressure less than 140mmHg systolic and less than 90mmHg diastolic

3. LDL “bad” cholesterol less than 160mg/dl

4. Fasting blood glucose less than 125mg/dl

5. Body mass index (BMI) less than 30kg/m2

At this point, you are probably asking what’s the catch? I can almost hear the disbelief, “By meeting just these five criteria my risk of ever having a heart attack goes away? Impossible!” In two prior blog entries, I discussed the studies behind these statistics in greater detail (see http://beyondapples.org/2009/06/23/the-end-of-cardiovascular-disease-part-1/, http://beyondapples.org/2009/06/29/the-end-of-cardiovascular-disease-part-2/). The short version is that the concept of heart attacks being almost entirely preventable come from multiple studies that followed young adults for 30 to 40 years to see who developed heart disease and who didn’t. By comparing people who had one or more of these risk factors when they entered the study to those who had none, the studies found that the vast majority of heart attacks occurred in people who already had one or more risk factors.

But there is a catch, of sorts: most adults in this country already have one or more of these risk factors. A large national study found that less than 1 percent of men ages 35 to 74 years old had optimal control of the major risk factors.**** Nine percent of women ages 35 to 44 had optimal control of their risk factors but by age 55 to 74 this decreased to less than 1 percent.

These sobering statistics tell us that we need to get more aggressive about heart disease prevention, especially in younger people. We have to catch people while they are still “risk factor free” and then partner with them to keep them that way. For those young people who we find already have one or more risk factors, it means we have move quickly to get their risk factors under control. Today we have more ways than ever to do that, but as I recently discussed, simply having the power to optimize our risk factors doesn’t necessarily mean that we actually do it (see http://beyondapples.org/2009/09/03/getting-hypertension-under-control/).

A couple months ago I decided to see where I stood on these five risk factors. I shot an email to my primary care doctor and asked him to order blood work. I already knew that I was a never smoker (criteria #1). I had my blood pressure checked at my last clinic visit, and it was well within goal (110/71; criteria #2). And given my weight (158 lbs) and height (5’11″), my BMI was optimal (22.0; criteria #5). When the labs came back, I was happy to learn that my LDL cholesterol was 103 (criteria #4) and my fasting glucose 84 (criteria #5). All five of my risk factors were under control. When it comes to coronary heart disease prevention, I am five for five.

So the question is: do you have your 5 risk factors for coronary heart disease under control? Do you meet these five criteria for CHD prevention? Are you five for five?

- Shantanu Nundy, M.D.

* The academic literature typically lists four risk factors — smoking, blood pressure, cholesterol, and blood sugar. Obesity was added because in young adults poor risk factor control is largely a result of weight gain.

** To put this statistic into perspective consider that only about 75 percent of lung cancers are preventable. This is because smoking causes 3 out of every 4 cases of lung cancer, and the vast majority of the remaining one-quarter have no known cause and therefore no means of prevention. Breast cancer is even less preventable. Studies show that through diet, weight control, and exercise women can lower their risk of developing breast cancer by about 30 percent.

*** Not surprisingly, for all of the above risk factors, the better your control the lower your risk of coronary heart disease. Therefore, making cutoffs for at-risk and not-at-risk is somewhat arbitrary. The cutoffs above are based on the clinical definitions of hypertension (criteria #2), dyslipidemia (criteria #3), diabetes (criteria #4), and obesity (criteria #5). One could also use more stringent cutoffs that identify “pre-disease,” or abnormal results that do not yet meet criteria for disease but are also not normal.

**** It is important to note that in this study the cutoff values were stricter than those presented above. For example, optimal LDL was defined as less than 130 mg/dl, compared to 160mg/dl suggested here.

References

Greenland P, Lloyd-Jones D. “Time to End Mixed Messages — And Often Incorrect — Messages about Prevention and Treatment of Atherosclerotic Cardiovascular Disease.” J Am Coll Cardiol, 2007; 50:2133-2135. http://content.onlinejacc.org/cgi/content/full/50/22/2133.