In this nationwide cohort study examining the impact of fluoroquinolones exposure on AA/AD incidence, our analyses revealed a 1.6-fold increased long-term risk of AA/AD among patients exposed to fluoroquinolones, with a significant association noted across nearly all subgroups that were analyzed. Using machine learning methods, we identified crucial factors contributing to AA/AD development in patients exposed to fluoroquinolones. The findings presented here are intended to assist healthcare professionals in creating systematic methods for the continuous observation and proactive prevention of AA/AD among individuals who have been treated with fluoroquinolone antibiotics to reduce the risk of potential health complications related to these antibiotics.
The mechanism underlying fluoroquinolones-induced AA/AD is not fully understood, although two hypotheses have been proposed. The first hypothesis posits that fluoroquinolones interfere with the integrity of the extracellular matrix, resulting in homeostatic dysregulation and impaired biomechanical strength in aorta, and ultimately triggering progressive aortic weakening, dissection, and rupture by upregulating the activity of matrix metalloproteinases (MMPs) and reducing the levels of tissue inhibitors of MMPs25,26. Increased MMP expression has been reported in smooth muscle cells in patients with abdominal AA27 and in cornea and tendons in animals exposed to fluoroquinolones14,28. The second hypothesis proposes that fluoroquinolones, which are DNA topoisomerase inhibitors, promote mitochondrial dysfunction, suppress cell proliferation, and induce apoptosis29,30, ultimately leading to aortic damage.
In addition to fluoroquinolones, risk factors of AA/AD include older age, male sex, lifestyle habits such as cigarette smoking and stimulant abuse, and clinical conditions such as COPD, prolonged hypertension, obesity, atherosclerosis, chronic kidney disease, trauma, vasculitis, bacterial infection, and congenital connective tissue disorders 31–33. Indeed, we also found that these previously reported factors were associated with AA/AD risk in Table 2. Further, we found that certain antihypertensive medications (ACEI/ARB, CCB, and beta-blockers) were associated with increased AA/AD risk. This finding contradicts previous studies linking the renin-angiotensin system to AA and suggesting that antihypertensive medications are beneficial for patient outcomes after the development of AA/AD34,35. One possible explanation for this discrepancy is that hypertension is a known risk factor for AA/AD36 and that individuals with hypertension are often prescribed these antihypertensive medications. Therefore, in the present study, the association of antihypertensive medications with increased AA/AD risk might reflect the presence of high blood pressure, a known AA/AD risk factor, in these patients.
Based on our machine learning analysis, the top ten important factors for the development of AA/AD in patients with fluoroquinolones exposure were age, comorbidities such as DM, hyperlipidemia, and COPD, and medications including intravenous steroids, insulin, CCB, beta-blockers, and ACEI/ARB. Of these, intravenous steroid use was the top-scoring predictor of AA/AD. Of note, antihypertensive medication use might reflect preexisting high blood pressure. As indicated in Table 2, which outlines the risk determinants for AA/AD, and Fig. 4, which ranks the important risk factors, most of the top ten significant factors for AA/AD are also related to an increased risk of AA/AD. The only exceptions are diabetes mellitus (DM) and insulin use, which may play a role in reducing the risk of AA/AD in patients exposed to fluoroquinolones. Overall, the results mentioned above offer important insights for tracking patients exposed to fluoroquinolones.
Glucocorticoids are often used in combination with fluoroquinolones for inpatients. However, a case series reported that treatment with anabolic steroids increased the risk of AD in athletes, particularly in association with exercise 37. Furthermore, Sendzik et al. reported that the combined use of steroids and fluoroquinolones increased the levels of MMPs and activated caspase 3, indicating apoptosis, in tenocyte cultures38. These results are consistent with the present study finding that steroid use, either intravenous or oral, might be associated with the development of AA/AD.
DM is a well-established risk factor for coronary and cerebrovascular diseases. However, the DM prevalence is surprisingly lower in individuals with abdominal AA than in those without abdominal AA (6–14% vs. 17–36%)39. In fact, a 3-year follow-up study found that DM was independently associated with reduced abdominal AA growth40. Similarly, Prakash et al. reported an inverse association between DM and the rate of hospitalization for thoracic AD41. In a meta-analysis including 14 studies and 15 794 patients, Li et al. found that the DM prevalence was lower in patients with AD than in those without AD (odds ratio 0.51, 95%CI 0.33–0.81)42. However, the mechanism underlying the beneficial effects of hyperglycemia in thoracic AD is not fully understood. In the present study, insulin had a beneficial effect and prevented the development of AA/AD. Insulin use may play an important role in the negative association observed between DM and the development of AA/AD.
Recent studies have increasingly shown the role of inflammation and macrophage infiltration in the development of AD43,44. In a murine model, Tomida et al. found that the use of indomethacin, an NSAID, prevented death due to abdominal AD and reduced the incidence of AD by up to 40%45. This effect might be attributed to the inhibition of monocyte transendothelial migration and blockade of the accumulation of monocytes/macrophages in the aortic wall. This is compatible with our findings, indicating the potential use of NSAIDs to prevent the development of AD.
The present study boasts several key strengths. Firstly, utilization of a nationwide database supports the generalizability of the study results. Secondly, the sample size and follow-up duration ensured a robust collection of AA/AD events. Thirdly, we employed machine learning methods were used to pinpoint important factors for the development of AA/AD in individuals exposed to fluoroquinolones. Lastly, the cohort study design minimized the risk of sampling bias, a common issue in case-control studies 46, that most previous research has used. Despite its strengths, the current study has a few potential weaknesses. Firstly, although the NHIRD database offered a large sample size, it did not include clinical information like imaging results, biochemical and microbiological data, blood pressure readings, and physical characteristics. Secondly, the study wasn't a randomized controlled trial, which meant that there were notable differences in the baseline characteristics of the two groups. However, to reduce these biases as much as possible, we used propensity score matching and multivariable adjustment. Finally, we were unable to confirm whether participants used fluoroquinolones before 2002 or after 2010 because of the limitations in our data availability and study design. Assuming the missing data was random in both groups, we could likely overlook the bias.