Abstract Background Emerging evidence indicates increased coronary atherosclerosis in amateur athletes. However, previous studies were limited by its cross-sectional design and limited sample size, preventing the exploration of sport specific associations with coronary atherosclerosis. Purpose We aimed to compare the incidence and progression of coronary artery calcification (CAC) between runners, cyclists and other types of athletes using a prospective cohort study with repetitive measurements. Methods Asymptomatic middle-aged men, who previously underwent a sports medical evaluation without abnormalities, were recruited in the Measuring Athlete's Risk of Cardiovascular events (MARC) study (n=318) and were asked to participate in this follow-up study. CT imaging was performed to assess CAC scores. Data was collected between 2012–2014 (i.e. baseline) and 2019–2020 (i.e. follow-up). We categorized participants as runners, cyclists or “other” sports (e.g. water polo, tennis, hockey, etc.) based on their dominant sport performance at baseline. Results We included 260 men in this interim analysis, with an average follow-up time of 6.3±0.5 years. Age (61.4±6.4 years), systolic blood pressure (143±20 mmHg), BMI (25.2±2.8 kg/m2), LDL-cholesterol (3.2±0.9 mmol/L), smoking (0.3 [0–8] pack years) and family history of coronary heart disease (28%) did not differ between runners (n=64), cyclists (n=75) and other athletes (n=121, all p>0.05). CAC was present in 137 (53%) men at baseline, which increased to 181 (70%) at follow-up. CAC scores increased from 1 [0–33] to 33 [0–129]. Cyclists had a lower CAC prevalence and CAC scores compared to individuals performing other sports at follow-up (Figure 1). Of those without CAC at baseline (n=123, 47%), cyclists less often developed CAC during follow-up compared with runners (adjusted OR=0.36 [0.17–0.79], p=0.01). In the entire cohort, CAC progression (ln delta CAC+1) was less prominent in cyclists than runners (adjusted B=−0.75 [−1.39 to −0.11], p=0.02), whereas progression of CAC in participants performing other sports did not differ from the runners. In participants with CAC at baseline, cyclists also had less CAC progression than runners (B=−0.49 [−0.95 to −0.02], p=0.04). Conclusion Cyclists have a lower incidence and less progression of CAC during 6 years of follow-up compared with runners and individuals performing other sports. Figure 1. Sport specific CAC prevalence and scores Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Hartstichting