What counts as a premature family history of coronary artery disease?

Atherosclerotic cardiovascular disease in a first-degree relative at a young age: a father or brother before age 55, or a mother or sister before 65. Second-degree relatives such as uncles or grandparents do not meet the definition. ASCVD here includes coronary disease (MI, angina or coronary stenosis), stroke or TIA, peripheral artery disease and aortic atherosclerotic disease.

Is diabetes still considered a CAD risk equivalent?

The phrase comes from ATP III (2001), which treated diabetes like established coronary disease when setting LDL goals. The 2026 ACC/AHA dyslipidemia guideline takes a different route: it recommends starting lipid-lowering therapy in adults 40 and older with type 1 or type 2 diabetes and uses the PREVENT equations to estimate risk in most other adults without ASCVD. Questions may still use the older phrase, so know both.

What are risk-enhancing factors in the 2026 ACC/AHA guideline?

Risk enhancers personalize a calculated risk estimate and help decide on lipid-lowering therapy. The guideline highlights a family history of premature ASCVD, chronic inflammatory disease such as lupus or rheumatoid arthritis, cardiometabolic conditions such as obesity, diabetes and chronic kidney disease, higher-risk ancestry such as South Asian or Filipino, and reproductive markers such as preeclampsia, gestational diabetes and early menopause, plus high Lp(a), apoB, hsCRP or triglycerides.

Why is lipoprotein(a) measured only once?

Lipoprotein(a) is an LDL-like particle whose apolipoprotein(a) is linked to apoB-100. Its level is largely genetically determined, stays fairly stable through life and barely responds to lifestyle change, so the 2026 guideline recommends measuring it at least once in adulthood without routine repeats. A level of 125 nmol/L (50 mg/dL) or higher carries about 1.4 times the long-term risk of heart attack or stroke.

Is male sex a risk factor for coronary artery disease?

Yes. Male sex is a non-modifiable risk factor for earlier and more severe atherosclerotic disease, and men's risk starts rising significantly around age 45. Women have lower risk before menopause, but theirs rises faster from around age 55, and by their seventies the incidence of MI in women exceeds that in men. Premature menopause raises a woman's risk further.

CAD Risk Factors Mnemonic: Modifiable vs Non-Modifiable

Remember the classic coronary artery disease (CAD) risk factors as CAD HITS: Cigarette smoking, Age, Diabetes, Hypertension, Increased LDL, Triglycerides high or HDL low, and Strong family history of premature disease. The non-modifiable risk factors are age, male sex, family history and ancestry (for example, South Asian); the modifiable ones are smoking, high blood pressure, dyslipidemia, diabetes, obesity, physical inactivity, unhealthy diet and excess alcohol, along with conditions such as chronic kidney disease and chronic inflammatory disease. For Step 2 CK, the 2026 ACC/AHA dyslipidemia guideline layers risk enhancers (inflammatory disease, adverse pregnancy outcomes, higher-risk ancestry, lipoprotein(a)) on top of a PREVENT risk score.

CAD HITS, letter by letter

Letter	Risk factor	Can it change?	How it drives plaque
C	Cigarette smoking, including secondhand smoke	Yes	Toxic to the endothelium; raises platelet reactivity and fibrinogen, raises LDL, lowers HDL and causes vasoconstriction
A	Age (ATP III counts men ≥45 and women ≥55)	No	CAD, peripheral artery disease and aortic aneurysm all rise steeply with age
D	Diabetes, type 1 or 2	Yes, by control	Advanced glycation end products and oxidative stress injure the endothelium
H	Hypertension	Yes	Shear stress activates the endothelium; risk climbs from pressures as low as 115/75 mm Hg
I	Increased LDL (and other apoB particles)	Yes	LDL enters the intima, is oxidized and is eaten by macrophages that become foam cells; risk tracks cumulative LDL exposure
T	Triglycerides high or HDL low	Yes	Triglyceride-rich lipoproteins add risk even on a statin; ATP III counts HDL <40 mg/dL, and HDL ≥60 mg/dL subtracts one risk factor
S	Strong family history of premature disease	No	Father or brother affected before 55, mother or sister before 65; includes inherited disorders such as familial hypercholesterolemia

How to use it: the A and the S are fixed; C, D, H, I and T are what prevention targets. Almost half of US adults have at least one of the three key risk factors: high blood pressure, high cholesterol or smoking. Metabolic syndrome (any three of central obesity, high triglycerides, low HDL, high blood pressure and high fasting glucose, in the ATP III definition) bundles several letters at once. Inherited lipid disorders are sorted in the familial dyslipidemias mnemonic.

Modifiable vs non-modifiable at a glance

Non-modifiable	Modifiable
Older age	Smoking and secondhand smoke
Male sex (women's risk climbs after menopause)	High blood pressure
Family history of premature ASCVD; inherited lipid disorders	High LDL, non-HDL cholesterol and apoB; high triglycerides; low HDL
Ancestry (for example, South Asian)	Diabetes and insulin resistance; obesity, especially central
Premature menopause	Chronic kidney disease
	Physical inactivity; diet high in saturated fat and refined carbohydrates; excess alcohol
	Chronic stress, depression and poor sleep
	Chronic inflammatory disease (rheumatoid arthritis, lupus, psoriasis) and HIV

Lipoprotein(a) sits in between: it is a lipid abnormality, but its level is largely genetic and lifestyle barely changes it, so it is measured once in adulthood.

Why these factors cause plaque (Step 1 mechanism)

Atherosclerosis is an inflammatory response to injury, such as shear stress from hypertension or oxidative injury from tobacco smoke:

ApoB-containing lipoproteins, mainly LDL, collect in the intima and are oxidized.
Activated endothelium expresses adhesion molecules (VCAM-1) that recruit monocytes.
Monocytes become macrophages, take up modified lipoprotein through scavenger receptors and turn into foam cells, the hallmark of the early plaque.
Smooth muscle cells migrate from the media and lay down collagen, building a fibrous cap over a necrotic lipid core.
Macrophage matrix metalloproteinases thin the cap; rupture exposes the thrombogenic core and triggers thrombosis. Plaque erosion is the second most common mechanism of acute coronary syndromes.

Draw the sequence yourself with the atherosclerosis pathogenesis walkthrough.

Step 2 CK: the classic list vs the 2026 ACC/AHA guideline

	ATP III (2001): the classic board list	2026 ACC/AHA dyslipidemia guideline
Risk estimate	Count risk factors; Framingham 10-year CHD risk if 2 or more	PREVENT-ASCVD equations: 10- and 30-year risk, ages 30–79
Risk categories	<10%, 10–20%, >20% (a CHD risk equivalent)	Low <3%, borderline 3% to <5%, intermediate 5% to <10%, high ≥10%
Diabetes	A CHD risk equivalent	Start lipid-lowering therapy at age 40 or older
Family history	One of the counted major risk factors	A risk enhancer used to personalize the estimate
LDL-C goals, primary prevention	<100, <130 or <160 mg/dL by risk group	<100 mg/dL if borderline or intermediate risk; <70 mg/dL if high risk
Extra tools	Optional in selected persons: emerging risk factors such as Lp(a) or subclinical atherosclerosis, to guide the intensity of therapy	Lp(a) once in adulthood; apoB; selective coronary artery calcium (CAC) scoring

The guideline's own shorthand is CPR: Calculate the PREVENT risk, Personalize it with risk enhancers, and Reclassify with a CAC score when the decision is uncertain. To remember the main enhancers, think risk enhancers light a FIRE:

Family history of premature ASCVD.
Inflammatory disease, such as lupus or rheumatoid arthritis.
Reproductive history: preeclampsia, gestational hypertension, gestational diabetes, preterm delivery, premature (<40) or early (<45) menopause, or polycystic ovary syndrome.
Ethnic ancestry with higher risk, such as South Asian or Filipino.
Plus the labs: lipoprotein(a) (≥125 nmol/L or ≥50 mg/dL carries about 1.4 times the risk), apoB, high-sensitivity CRP and triglycerides.

Other key points: adults 40 and older with diabetes, stage 3 or worse CKD, or HIV should start lipid-lowering therapy; CAC scoring fits men 40 and older and women 45 and older at borderline or intermediate risk when the result would change the statin decision; any coronary calcium supports an LDL-C goal below 100 mg/dL, while a score of zero can support deferring a statin in a low- or intermediate-risk patient without other cardiovascular comorbidities; and patients with ASCVD at very high risk aim for an LDL-C below 55 mg/dL. Drug choices are in the statins overview.

Exam traps

Two different age cutoffs. Age as a risk factor (ATP III): men ≥45, women ≥55. Premature family history: male relative <55, female relative <65.
Only first-degree relatives count. An uncle or grandparent with an early MI does not meet the definition.
"CHD risk equivalent" is ATP III language. The 2026 guideline instead starts lipid-lowering therapy at 40 or older with diabetes, CKD stage 3 or worse, or HIV.
Diabetes hides ischemia: silent myocardial ischemia occurs particularly in patients with diabetes.
HDL is not a free pass: the relationship between HDL and risk is U-shaped.
Triglycerides are not in the ATP III count of major risk factors, yet hypertriglyceridemia is an independent risk factor.
Pregnancy history is cardiac history: ask about preeclampsia, gestational diabetes and early menopause; see the preeclampsia overview.
Smoking may predict MI more strongly in women than in men.

Worked example (Q-bank style)

Vignette. A 48-year-old man comes for a checkup. He smokes a pack a day, and his blood pressure is 146/92 mm Hg on two visits. Fasting lipids: LDL 150 mg/dL, HDL 38 mg/dL, triglycerides 210 mg/dL. His father had an MI at 61, his brother had a coronary stent placed at 51, his mother had an MI at 70, and a paternal uncle died of an MI at 44. Which detail meets the definition of a premature family history of ASCVD?

A. Father's MI at 61 B. Brother's coronary stent at 51 C. Mother's MI at 70 D. Paternal uncle's MI at 44 E. None of the above

Answer: B. A brother is a male first-degree relative, and 51 is under 55.

Choice	Why it is wrong
A. Father at 61	Male first-degree relatives count only before 55
C. Mother at 70	Female first-degree relatives count only before 65
D. Uncle at 44	Young, but an uncle is a second-degree relative
E. None	The brother qualifies

Follow-up: how many ATP III major risk factors besides LDL does he have? Five: age (a man 45 or older), smoking, hypertension, HDL below 40 mg/dL and premature family history. His triglycerides are high but are not one of the counted five; under the 2026 guideline they are a marker that refines risk.

Step 2 CK add-on: calculate his 10- and 30-year PREVENT risk, personalize it with the enhancer (his brother's early disease) and measure lipoprotein(a) once. If his 10-year risk is 10% or higher, the LDL-C goal is below 70 mg/dL; if borderline or intermediate, below 100 mg/dL. Smoking cessation and blood pressure control apply either way.

Key takeaways

CAD HITS: Cigarettes, Age, Diabetes, Hypertension, Increased LDL, Triglycerides or low HDL, Strong family history.
Non-modifiable: age, male sex, family history and genetics, ancestry, premature menopause.
Modifiable: smoking, blood pressure, lipids, diabetes, obesity, inactivity, diet, alcohol, CKD and chronic inflammation.
Premature family history: first-degree male relative before 55, female before 65.
2026 ACC/AHA: PREVENT risk (ages 30–79), risk enhancers (FIRE plus labs), CAC when unsure, lipoprotein(a) once, LDL-C goals of <100, <70 and <55 mg/dL by risk.