A Country Doctor Writes:

People are asking about the latest US Public Health Service Taskforce on Prevention (USPSTF) recommendation about the use of aspirin to prevent heart disease. It has been a long-standing recommendation for people who already have heart disease.

When I turned 50, I started taking a “baby” aspirin. That was their recommendation then. I stopped taking mine because I had several nosebleeds. “It’s not worth it for me”, I told my patients. Some time later, they changed their recommendation to men over 50 but only women over 50 with diabetes (because their risk for heart disease is four times that of non-diabetic women).

The reason their recommendation keeps changing (negative view) or evolving (positive view) is that studying what happens to large groups of people who do this, that or the other over periods of many years is difficult, expensive and fraught with technical and procedural problems.

It boils down to two numbers: the number needed to treat in order to avoid one bad event, NNT, and the number needed to harm one person. When I wrote about aspirin for heart disease prevention in 2017, the number of aspirin recommendations needed to avoid one cardiac event was about 200. I didn’t know the number needed to harm then.

The harm can be a lot worse than the nosebleeds I had. Some people get bleeding ulcers or even cerebral hemorrhages that may be partly due to their aspirin use.

So last week their recommendation was revised based on more recent data. It seems the risk is greater than the benefit for people over 60 – again, we are talking about primary prevention, people who do not yet have heart disease.

Patients often worry when we change our advice because of new scientific evidence. I understand their confusion and their calls, but I don’t worry much about this change: It doesn’t keep me up at night or on the phone with patients after hours. We need to remember the NNT. It takes 200 aspirin recommendations to prevent one heart attack. That means that roughly 0.5% of people taking aspirin will be helped by it and the rest will not – but in some subgroups the benefit is greater and in some subgroups of people there will be more harm than good.

The latest recommendation includes the patient’s ten year cardiovascular risk, so the USPSTF no longer treats all men over 50 the same. The ten year risk can be calculated from a person’s sex, age, blood pressure, smoking status, presence of diabetes and diagnosis of hypertension. The American Heart Association and the American College of Cardiology created this risk calculator/smartphone app in 2013.

Here is their latest recommendation:

The USPSTF concludes with moderate certainty that aspirin use for the primary prevention of CVD events in adults ages 40 to 59 years who have a 10% or greater 10-year CVD risk has a small net benefit.

The USPSTF concludes with moderate certainty that initiating aspirin use for the primary prevention of CVD events in adults age 60 years or older has no net benefit.

So, remember that a lot of people will still be taking aspirin for nothing. But think of it like wearing your seatbelt: as long as it doesn’t hurt you, what do you have to lose – even if you never get in an accident? But the big concern with recommendations about primary prevention is that our recommendations could end up hurting people who never had a big risk of getting the disease we are trying to prevent. Then our advice could hurt innocent people. And that is what the USPSTF is now saying about seemingly healthy 60-year olds. (More people are hurt by aspirin than by seatbelts.)