In middle-aged individuals, the yearly conversion rate from zero CAC to non-zero CAC score is approximately what percent?

• A. 1%
• B. 5%
• C. 3%
• D. 7%

Answer: (B)

The key idea is the rate at which subclinical coronary atherosclerosis can begin to show up as detectable calcium in someone who starts with zero calcium. In middle-aged adults, longitudinal imaging studies show that about 5% per year convert from zero CAC to a non-zero CAC score. This reflects the ongoing development of atherosclerotic plaque even in people who initially have no detectable calcium, and it helps explain why baseline zero does not guarantee zero future risk. The exact rate can vary with age, sex, ethnicity, and risk factors like smoking, hypertension, high LDL, and diabetes, but around 5% per year is the commonly cited estimate. Rates as low as 1%–3% or as high as 7% are less consistent with typical midlife data.