Burden of subclinical coronary atherosclerosis among asymptomatic adults: the REACH-Rural India Study.

Background: Coronary artery calcification (CAC) serves as a robust marker of subclinical atherosclerosis and an independent predictor of cardiovascular disease (CVD). Despite its clinical significance, population-based evidence on CAC prevalence and its determinants in rural India remains limited. This study aimed to estimate the prevalence of CAC and evaluate its association with cardiometabolic risk factors among adults aged 35-65 years in a rural Indian population. Methods: A total of 3006 individuals aged 35-65 years were selected and invited to participate in the REACH (Risk Evaluation of Subclinical Coronary Health)-Rural India Study. From 2022 to 2024, the study enrolled asymptomatic adults with no history of cardiovascular events from rural communities in the Coimbatore and Tirupur districts of Tamil Nadu, India. Data collection included sociodemographic and clinical profiling, laboratory testing, and carotid intima-media thickness (cIMT). CAC was quantified using the Agatston scoring method from dual-source CT scans. Findings: In total 2961 participants included in the final analysis (mean age 49.8 ± 8.3 years; 52.8% women), the overall prevalence of coronary artery calcification (CAC) was 25.6%. Prevalence was significantly higher in men (33.5%) than in women (18.5%) (p < 0.001). The prevalence of severe CAC (Agatston score >400) was threefold higher in men and most common in those aged 56-65 years. However, no detectable CAC was observed among women aged 35-45 years. The distribution of CAC scores was as follows: 7.0% had minimal CAC (1-10), 11.4% mild (11-100), 5.2% moderate (101-400), and 1.9% severe (>400). Multivariable logistic regression showed that diabetes, hypertension, overweight/obesity, and abnormal CIMT were independently associated with CAC. Among men, current smoking was also significantly associated (OR = 1.51; 95% CI: 1.18-1.93). In total, 83.5% of individuals with CAC had one or more cardiovascular risk factors. No significant associations were observed between CAC and elevated creatinine, reduced eGFR and peripheral artery disease (PAD) after full adjustment. Interpretation: This study reveals a substantial burden of CAC in a rural Indian population, with prevalence patterns comparable to urban cohorts in Western countries. The findings underscore the need to incorporate CAC screening in individuals with metabolic risk factors, especially in underserved populations, to identify early subclinical atherosclerosis and reduce CVD risk. Funding: Indian Council of Medical Research (ICMR), (REF No. 5/4/1-9/2020-NCD-1).