Abstract Body (Do not enter title and authors here): Background
Coronary artery calcium (CAC) is commonly measured using the Agatston score. Prior work has shown that inclusion of measures of CAC distribution, such as the number of coronary vessels with involved CAC and the relative distribution of CAC burden across different vessels, may improve cardiovascular risk prediction. However, the long-term predictors of CAC distribution at older age have not yet been explored.

Aims
We aimed to characterize the patterns of distribution of CAC in adults ≥ 75 years and identify risk factors associated with a more diffuse CAC distribution.

Methods
Time-weighted average exposure to traditional cardiovascular risk factors (e.g., blood pressure, LDL-C, HDL-C, BMI) was calculated over a 30-year period, using ARIC data from Visit 1 (1987-1989) to Visit 7 (2018-2019). ARIC conducted cardiac CT at Visit 7, and the CAC “diffusivity index” was calculated as 1 - (CAC in most affected vessel/total CAC). Participants with a diffusivity index >75^th percentile were classified as having a diffuse CAC phenotype. Multivariable logistic regression was used to quantify the associations between time-averaged risk factors and diffuse CAC phenotype. Ordinal logistic regression was used to identify predictors of the number of coronary vessels with any CAC (0-4 [including left main]).

Results
Of 2,143 participants (62% female, mean age 49 at Visit 1 and 80 at Visit 7), the mean diffusivity index was 0.28 (SD 0.23). In adjusted models, SBP ≥140 mmHg and HDL <35 mg/dL were associated with diffuse plaque phenotype. Other predictors included ever smoking (OR 1.52, 1.22-1.91), male sex (OR 2.12, 1.67-2.70), and limited education (OR 1.49, 1.03-2.14) (Table 1). SBP ≥140 mmHg (ordinal OR 2.06, 1.44-2.96), LDL ≥160 mg/dL (OR 2.28, 1.35-3.90), HDL <35 mg/dL (OR 2.78, 1.96-3.95), BMI ≥30 kg/m² (OR 1.54, 1.02-2.32), ever smoking (1.47, 1.24-1.73), and limited education (OR 1.35, 1.00-1.80) were associated with increasing number of vessels with CAC.

Conclusion
Traditional risk factors such as hypertension or low HDL-C are strong graded risk factors of a more diffuse CAC phenotype in older adults age >75. Men, individuals with a smoking history, and those with limited education also had more diffuse CAC.