Stroke is the second leading cause of death and disability worldwide. The incidence and recurrence of stroke are strongly associated with the management of modifiable vascular risk factors, including hypertension (HT), diabetes mellitus (DM), dyslipidemia, and atrial fibrillation (AF) [1,2]. Although modifiable risk factors are important to reduce the risk of stroke, awareness of risk factors and the control rate of risk factors in many patients with stroke remain low, especially in young adults [1,2]. Given that there is little information on the clinical factors related to uncontrolled risk factors for stroke, we aimed to investigate the proportion of new diagnoses of major risk factors for ischemic stroke and identify the factors associated with the poor control rate using a linked dataset of stroke in Korea.

The study was approved by the Institutional Review Board (IRB) of Seoul National University Hospital (IRB No. H-1608-078-785), those of other 34 participating hospitals, and the Health Insurance Review and Assessment Service (HIRA). The need for informed consent was waived by the IRBs.

We included data for 42,879 patients with acute ischemic stroke within 7 days after symptom onset from the linked Clinical Research Center for Stroke Registry and the HIRA between January 2008 and December 2014. We evaluated the proportion of patients with newly identified conventional risk factors (HT, DM, and AF) after index ischemic stroke and assessed factors related to poor control of risk factors. Detailed methodological descriptions and statistical analyses are provided in Supplementary methods. Among the total patients included (n=42,879; 59.5%, male [n=25,529]; mean±standard deviation age, 65.7±12.5 years), 78.0% (n=33,462) were hypertensive, 33.2% (n=14,242) were diabetic, and 9.5% (n=4,069) had AF with cardioembolic stroke. Among patients with HT, 8.8% (2,956/33,462) were newly diagnosed with HT. Similarly, 5.0% of the patients (n=709) were newly diagnosed with diabetes, and 15.9% of the patients (n=648) were newly diagnosed with AF after stroke (Supplementary Tables 1-3). The detailed baseline characteristics are discussed in the Supplementary Results. Young-age patients (≤45 years) were more likely to have newly identified vascular risk factors after index stroke (Table 1). After adjusting for confounding variables, younger age (≤45 years) was independently associated with a higher proportion of newly identified risk factors (odds ratio [OR], 1.865; 95% confidence interval [CI], 1.579 to 2.203; P<0.0001 in HT, OR, 1.726; 95% CI, 1.163 to 2.562; P=0.0067 in DM, and OR, 2.503; 95% CI, 1.507 to 4.155; P=0.0004 in AF) (Table 2). Furthermore, factors related to newly diagnosed HT were smoking (OR, 1.336; 95% CI, 1.191 to 1.497; P<0.0001) and other comorbidities were negatively associated with newly diagnosed HT. Among patients with DM, only the presence of HT was negatively associated with newly diagnosed DM, while other factors were not significant. In addition, no factors other than young age were identified for newly diagnosed AF (Table 2).

Using the linked dataset, we found that age ≤45 years was an independent factor associated with newly diagnosed major stroke risk factors after index stroke. Furthermore, patients with other comorbidities were less likely to have a new diagnosis of risk factors after index stroke. Traditional vascular risk factors account for up to 90% of the attributable risk of stroke development. Therefore, the most effective way to reduce the incidence of stroke is to control modifiable risk factors [3,4]. However, <50% of the public possesses knowledge of stroke, its risk factors, and warning signs [2,3]. According to public surveys, lower socioeconomic status, lower education, and younger age are associated with a lack of knowledge of stroke risk factors [1,3]. Consistent with previous reports, our findings revealed that age ≤45 years was an independent risk factor for newly identified major stroke in patients with index ischemic stroke [1,2]. Young people do not usually seek medical attention to identify vascular risk factors. Otherwise, they become aware of having risk factors during medical examinations for other purposes [2,3]. This partly explains why patients with comorbidities have a lower probability of a new diagnosis of vascular risk factors. Based on these results, regular check-ups during clinic visits could be an important and effective strategy for stroke prevention by identifying and controlling vascular risk factors.

Our study has several limitations. First, there could be a certain degree of unmeasured bias due to the retrospective design using a linked dataset. Second, the linked dataset did not contain data related to knowledge of risk factors in laboratory information and lifestyle aspects of patients, such as healthcare check-up results and socioeconomic status information. Third, we did not investigate risk factor awareness using a questionnaire during hospitalization. However, the status of risk factor management prior to index stroke was evaluated using the linked data. Fourth, we excluded 8.8% of the patients (n=4,578) with inaccurate information due to censored claims data after index stroke. Therefore, these factors may have affected our results.

In conclusion, this study showed that the proportion of patients with uncontrolled risk factors before index ischemic stroke was higher in younger patients (≤45 years). Public education about regular check-ups may contribute to an improvement in the control rate of risk factors to reduce stroke risk. Further large-scale studies are needed to confirm the relationship between clinical factors and control of risk factors among patients with ischemic stroke.