This study is the largest stroke registration study to date in Xi’an, China. The results of the present study showed that a small number of patients with MIS experienced stroke recurrence, disability, and death during the 1-year follow-up period. Nevertheless, these results are not optimistic. Hence, the risk factors associated with poor clinical outcomes at 1 year after MIS need to be further investigated. The results suggested that the risk factors associated with poor outcomes at 1 year after MIS stroke (i.e., recurrence, disability, and death) were not entirely consistent in Xi’an, China. Therefore, clinicians should apply early prevention strategies on an individual basis.
The results further showed that the prevalence of stroke recurrence at 1 year after MIS in the Xi’an region of China was 3.4%, which was lower than the prevalence of 13.2% at 1 year and that of 9.8% at 3 months reported by the China National Stroke Registry (CNSR) study[6, 15]; lower than the stroke recurrence prevalence of 7.6% in the Clopidogrel in high-risk patients with the Acute Non-disabling Cerebrovascular Events (CHANCE) study; also lower than the stroke recurrence prevalence of 6.1% by analysis of the Korean Multicenter Stroke Registry; but close to the stroke recurrence prevalence of 3.7% recently reported by the TIAregistry.org project. Besides, our data also revealed lower mortality (3.3% vs. 6.3%) and disability (9.3% vs. 17%) at 1 year as compared with the CNSR study , but with a comparable mortality (3.3% vs. 4.1%) to the Korean Multicenter Stroke Registry study at 1 year after MIS. These results suggested that the clinical outcomes of patients with MIS may differ among countries and regions. In addition to the differences in study designs, the prevalence of clinical outcomes may also be related to geographical environments, daily habits, economic status, and disease prevention measures, indicating the importance of studies of regional stroke registries.
There are several potential reasons for the lower prevalence of stroke recurrence, disability, and all-cause mortality at 1 year in the present study. First, there were notable differences in the clinical characteristics between our study and previous studies. As compared to the CNSR study, patients included in the present study had lower prevalence of hypertension (68.5% vs. 73.6%), DM (21.6% vs. 27.3%), dyslipidemia (6.9% vs. 11.8%), atrial fibrillation (4.8% vs. 5.8%), and previous stroke (26.5% vs. 31.1%), as well as lower NIHSS scores on admission (median, 1 vs. 2). Hence, the prevalence of risk factors for clinical outcomes of stroke in this region was relatively lower, which may be related to the better preventive measures and lifestyles in the Xi’an region, as compared with other regions. Second, differences in study designs and regions may have led to the differences in results. The CNSR study was a nationwide survey[6, 15] and, thus, did not represent the status quo. The datas assessed in the present study were collected from four tertiary grade A hospitals in the Xi’an region, which corresponding to the lower valley of the Wei River in the Guanzhong Plain in northern China. The relatively lower prevalence of poor outcomes may be due to more standardized regimens for the diagnosis, treatment, and prevention of secondary stroke than those in the CNSR study, which included primary, secondary, and tertiary hospitals. Other potential reasons for the lower prevalence of poor outcomes in the present study might be that most of the patients resided in urban areas of the Xi’an region and more than 90% had medical insurance.
Risk factors affecting the 1-year outcomes (i.e., stroke recurrence, disability, and all-cause mortality) after MIS in the Xi’an region of China were investigated. In the present and previous studies, age was identified as an independent risk factor for stroke recurrence, disability, and all-cause mortality at 1 year after MIS [19, 20]. Hence, older patients should be closely monitored for various indicators and early detection and treatment.
In addition, pneumonia was identified as an independent risk factor for stroke recurrence, disability, and all-cause mortality at 1 year after MIS in the Xi’an region, similar with the findings of previous studies[21, 22]. Pneumonia is closely related to dysphagia caused by stroke, suggesting that treatment for swallow difficulties after stroke must be improved in the Xi’an region. So, clinicians should promptly evaluate patients with dysphagia and initiate swallow rehabilitation, dietary guidance, and education of dysphagia in order to reduce the prevalence of pneumonia after MIS and improve treatment outcomes.
Similar to previous studies[23-25], current smoking was found to be an independent risk factor associated with 1-year stroke recurrence after MIS. After stroke, persistent smoking increases the risk of stroke recurrence. There exists a dose-response relationship between smoking quantity and the risk of stroke recurrence[24, 25] because smoking increases the short-term risk of stroke by promoting thrombosis and reducing cerebral blood ﬂow via arterial vasoconstriction [26, 27]. Therefore, it is important to control smoking among MIS patients.
In this study, an elevation in ALP levels was an independent risk factor for all-cause mortality, in accordance with the findings of previous studies[28-30]. Elevated ALP was related with an increased risk of all-cause mortality in patients with end-stage renal disease [28, 29] and as an independent predictor of poor outcomes of patients with preserved kidney function in the CNSR study. As a possible explanation, serum ALP has been implicated in the pathogenesis of vascular calciﬁcation and subclinical atherosclerosis[31, 32]. Vascular calciﬁcation plays a signiﬁcant role in the process of atherosclerosis and also leads to increase vascular stiffness and reduce vascular compliance. So, clinicians should pay more attention to ALP levels in patients with MIS, as early detection and intervention may reduce the risk of death within 1 year after stroke.
In the present study, the NIHSS score and leukocyte count on admission were identified as risk factors for stroke disability at 1 year after MIS, which was consistent with the findings of previous results[33-36]. A higher NIHSS score indicates severe neurological impairment. Because there is no specific treatment for cerebral function injury caused by stroke, the outcomes of the majority of patients with severe neurological impairment were generally poor. Previous studies have reported that a high leukocyte count in the early stage of stroke was closely related to the severity of stroke and co-infection, which led to aggravation of stroke and subsequent disability[37, 38]. However, an elevated leukocyte count in the early stage of stroke may not necessarily be caused by infection, thus the clinician should assess the presence of co-infections. For non-infectious stroke, the patient’s family members should be informed of a potentially poor outcome as early as possible. Early prevention and treatment of digestive tract ulcers and acute brain-heart syndrome may be hampered by a state of stress.
In addition, multivariate analysis showed that alcohol seemed to be a protective factor. The possible explanation is that we only recorded whether the alcohol used or not, but did not record the amount of alcohol consumed. However, based on the clinical characteristics, the mean age was higher in the patients with MIS who had adverse outcomes (include stroke recurrence, disability, all-cause mortality) at 1-year follow up. This may be due to the fact that most of the patients were in good health before the onset, more patients may have previously drunk alcohol. This phenomenon may lead to the tendency of alcohol consumption to be a protective factor in our multivariate analysis, but the result was not statistically significant.
There were some limitations to this study that should be addressed. First, the four hospitals participating in this study were not selected at random, thus there was potential for selection bias when evaluated the real burden of the disease in the Xi’an region of China. In addition, all the participating hospitals were level 3 first-class hospitals that may not necessarily represent the status quo of MIS treatment in community hospitals. Second, the focus of this study was the influence of risk factors on admission and during hospitalization on 1-year outcomes, so potential factors after discharge were not analyzed. Third, the data obtained from cerebrovascular and neurological imaging in this study were incomplete, so there were a lack of image-related risk factors, such as infarct volume and infarct location. Forth, in this study, 131 (10.5%) patients were lost to follow-up at 1 year after MIS. However, the sensitivity analysis showed that the patients lost to follow-up in this study were nearly random, which did not affect the results.