Lower cardiorespiratory fitness is associated with coronary artery atherosclerosis in individuals with a zero CAC score – cross-sectional results from SCAPIS

BACKGROUND AND AIMS: Despite a coronary artery calcification (CAC) score of zero, 5-6 % of middle-aged individuals still exhibit underlying atherosclerosis. This cross-sectional study aimed first to investigate the association between estimated cardiorespiratory fitness (CRF) and atherosclerosis in individuals with zero CAC, second to assess whether adding CRF to the Systematic Coronary Risk Evaluation (SCORE) model improves the explained variance in atherosclerosis, and third to characterise the association across CRF levels. METHODS: ) using submaximal cycle testing, CAC was assessed by non-contrast computed tomography, and atherosclerosis by coronary computed tomography angiography. Logistic regression and Chi-squared tests analysed associations and compared prevalences across CRF groups. RESULTS: higher CRF was associated with 4.5 % lower odds of atherosclerosis (p < 0.01), while one percentage point higher SCORE corresponded to 47.4 % higher odds (p < 0.01). The combined CRF-SCORE model explained significantly more variance in atherosclerosis than SCORE alone (p < 0.01). When categorised as "low" and "high", atherosclerosis prevalence was 104 % higher in low-CRF men (p < 0.01) and 127 % higher in low-CRF women (p < 0.001) compared to high-CRF counterparts. CONCLUSIONS: In individuals with zero CAC, low CRF was associated with more than double the prevalence of atherosclerosis compared to high CRF. Adding CRF to SCORE explained a greater proportion of variance in atherosclerosis. These findings suggest that CRF could help identify individuals at elevated risk, beyond traditional assessments.