In this study, we found that the prevalence of significant CAD detected by CCTA was significantly higher among asymptomatic adults with newly detected DM than asymptomatic adults without DM. Among those with coronary artery stenosis, the number of coronary vessels with significant obstruction was also higher, implying greater extent of CAD. Independent risk factors for CAD included age, gender, higher low-density lipoprotein level, and presence of diabetes mellitus, which were in line with commonly known risk factors of ASCVD24.
Type 2 DM is a multisystem disease causing vascular endothelial dysfunction, diabetic dyslipidemia, and chronic inflammation through complicated mechanism involving hyperglycemia, hyperinsulinemia, and insulin resistance, leading to the formation of atherosclerosis, and eventually, cardiovascular disease25. Due to the strong association between DM and ASCVD, DM was also considered to be a ‘CAD risk equivalent’26, although this concept was still under debate27. Delay between the onset of hyperglycemia and diagnosis of DM was common and estimated to be 4–6 years in average28. During the period of untreated hyperglycemia, complications might occur and progress prior to the clinical diagnosis of DM. In a study in Taiwan, 18.2% of newly diagnosed DM patients was found to have diabetic nephropathy, and 25.5% of patients already had retinopathy8. Similarly, we hypothesized that CAD might have developed before the detection of DM. In this study, the high prevalence of significant CAD in participant with newly detected DM supported our hypothesis.
CCTA was able to provide more detailed information about plague distribution and the degree of vascular stenosis and had been proven to improve risk stratification for CAD14, 15, even in asymptomatic patients with DM29. However, the benefits of screening CAD with CCTA in asymptomatic patients had not been confirmed30, and routine use of CCTA might increase risks of radiation and contrast medium exposure31. Studies had been done to evaluate the role of CCTA in high risk asymptomatic patients with DM, but the results remained controversial32.
In a previous study regarding detection of CAD using CCTA with 44 asymptomatic patients who had been diagnosed DM within 1 year and 44 matched controls, patients with newly diagnosed DM were more often to have coronary artery calcifications (66% vs 48%, p < 0.05). However, the prevalence of coronary obstruction (≥ 70% stenosis) did not show significant difference (9.1% vs 6.8%, p = 0.50)17. In our study, with a larger sample size, significant difference in the prevalence of significant CAD (≥ 50% stenosis) between participants with newly detected DM and participants without DM was found (40.7% vs 20.1%, p < 0.0001).
Several studies had been published regarding association between the duration of hyperglycemia and the risks of CAD. In a study conducted by Gurudevan et al., higher prevalence of obstructive CAD (≥ 60% stenosis) was found in participants with impaired fasting glucose as compared to participants with normal fast glucose (29.5% vs 13.3%, p = 0.02)33. Kim et al. investigated the results of CCTA in asymptomatic patients with different duration of DM, and found that longer duration was associated with higher risk of significant CAD (≥ 50% stenosis) (49.1%, 29.6%, and 28.3% in patients with DM duration ≥ 10 years, 5–10 years, and < 5 years, p < 0.001)34. These findings implied that the patients were already at higher risk of CAD at the diagnosis of DM, and the risk increased with time after the diagnosis.
In this study, we aimed to investigate the prevalence of significant CAD in asymptomatic community-dwelling participants at the time of DM detection. As many as 40.7% of the participants with newly detected DM was found to have significant CAD in our study. Established guidelines had suggested that thorough evaluation and management including risk factor modification, preventive pharmacotherapy, functional assessment, and, if needed, invasive coronary angiography should be carried out for patients with ≥ 50% stenosis in any of the coronary arteries found using CCTA22, 23. However, with the high prevalence of significant CAD in newly diagnosed DM patients, the importance of early CAD detection should also be highly considered in this population.
Several limitations should be noted when interpreting the results from this study. First, data was collected from clinical health examination at a single medical center. CCTA was also performed based on the participants’ decision, and this could cause selection bias. Nevertheless, the average age of newly detected DM was 58.6 ± 7.5 in our study, and was similar to the finding from a previous nationwide cohort study in Taiwan35. In addition, more male participants had newly detected DM than female, and this was also consistent with current observations35. Second, information about plaque composition and plaque burden were not provided in some of the reports of CCTA, thus making it difficult for further analysis of plaque characteristics. Nevertheless, the data on stenosis in the coronary arteries was complete without missing data, and significant findings could be derived from the results. Third, although the participants labeled as newly detected DM in our study had already met at least one of the diagnostic criteria of DM, more information would be needed to confirm this diagnosis. Finally, this was a cross-sectional study, and further follow-up data of the participants was unavailable. Further investigation would be needed to elucidate the course of CAD development in patients with DM.