Our study revealed the following two new findings. After adjusting for confounders, multivariable logistic regression analysis showed that: 1) SAP was a strongly predictor for abnormal oral hygiene in hospitalized ischemic stroke patients, followed by the number of dental caries, age and BI; 2) Oral hygiene cleanliness was an independent risk factor for predicting SAP, while the BI was a protective factor in hospitalized SAP patients. To our knowledge, this is the first investigation and predictive model of oral hygiene and SAP in acute ischemic stroke patients, which may be helpful for guiding clinical nursing work.
Previous studies have found that HAP is closely related to oral health [22, 23]. Any inflammation or damage to the oral mucosa could promote bacterial adhesion, colonization, reproduction and infection [24, 25]. Migration of this infection through the upper respiratory tract to the lower respiratory tract is common in clinical practice . Therefore, maintaining the integrity of the oral mucosa through daily care is very important to prevent secondary nosocomial infections . However, oral care is not limited to the oral mucosa; the gums, teeth, lips and tongue, and even salivation are included in daily clinical nursing work. The BOAS is a scale containing the five above mentioned items, which should be addressed in oral care . The scale is not only used for the evaluation of nursing care but also to guide nursing intervention for critically ill patients [20, 21, 26].
Among critically ill patients, stroke patients are susceptible to HAP not only in patients at the early stage but also in the recovery period; furthermore, the incidence of this acquired pneumonia among stroke patients is significantly higher than that of the general patient population [6, 27]. In the past 10 years, SAP has been widely recognized by clinical researchers [2–4, 7, 9]. The causes of this complication may be related to the stroke-induced immunosuppression, weakening of the pharyngeal reflex, the loss of proprioception or superficial sensation of the oral mucosa, and a weakening of the ability of the lips and tongue to push food into the pharynx after brain injury [7, 8, 10, 11, 17]. Therefore, screening the risk factors for and establishing a prediction model of oral hygiene in stroke patients is helpful to prevent SAP, HAP or other types of pneumonia in clinical work .
There were no significant differences in gender, disease duration, educational background, gastrointestinal diseases, or risk factors of vascular diseases, especially in some subjective evaluation indicators of oral hygiene between the two groups in cohort 1. However, in terms of objective indicators, age, SAP, the number of dental caries, the use of indwelling gastric tubes, and the WST, NIHSS and MMSE score were anatomically or functionally closely related to abnormal oral cleanliness in ischemic stroke patients. These results indicated that 1) the risk of oral hygiene abnormalities increases with age, suggesting that we need to pay more attention to the oral cleanliness of elderly patients with acute ischemic stroke; 2) objective abnormalities of the internal anatomy or pathological structure of the oropharynx and / or respiratory tract may be an important factor of abnormal oral hygiene in ischemic stroke patients, suggesting that we should seriously consider the prevention of dental caries and the management of chest infection and / or indwelling gastric tubes; and 3) cognitive function strengthening and ADLs rehabilitation may help improve oral cleanliness in patients with acute ischemic stroke.
Moreover, we analyzed 70 SAP patients in this study independently and compared them with non-SAP patients matched by age and gender. The results showed that there were significant differences in the WST score, indwelling gastric tube, NIHSS score, and BI between SAP and non-SAP patients. Particularly, these indicators were significantly more severe in the SAP group than in the non-SAP group. Interestingly, the SAP group had significantly higher BOAS scores than the non-SAP group. Therefore, is poor oral hygiene an independent risk factor for SAP? This point has not been raised in the previous literature, and we conducted the following analysis.
Our study found that there is a strong correlation between SAP and BOAS score abnormalities. In general, abnormal oral hygiene was most closely related to personal hygiene habits. However, this situation may change in the presence of certain diseases, such as nutritional or exercise-induced immune suppression, long-term use of antibiotics, dehydration, etc [28–30]. Little has been reported regarding whether lung infections affect oral hygiene . This study found that SAP may be the leading risk factor for abnormal oral hygiene in patients with acute ischemic stroke, although the exact reason is not clear. Surprisingly, the BOAS score was an independent risk factor for SAP, suggesting that abnormal oral hygiene has a higher risk coefficient than swallowing disorders, which is different from previous studies [8, 9]. Combined with two multiple regression analyses, we determined that oral hygiene abnormalities and SAP interact with each other and that this interaction may form a vicious cycle (Fig. 3). This is an important discovery that has not been reported before.
Dental caries have been recognized as one of the three major human diseases, along with parallel with cancer and cardiovascular diseases [31, 32]. Its etiology is complex and may be related to bacteria, the oral microenvironment and the time of action . Carbohydrates are the main source of food for Chinese people. A small amount of starch is easily deposited on the tooth surface after the meal and then forms a mixture with the trace protein in the saliva. With a suitable temperature and sufficient time, bacteria and even parasites and viruses can easily reproduce, and visible plaque and unpleasant oral odors are quickly generated [32, 34]. From the perspective of pathophysiology, caries is the result of long-term adhesion of plaque to teeth and destruction of organic matter [33, 34]. Patients with dental caries are more likely to have food residues in the cavities after meals, which makes it difficult to completely remove plaque. Therefore, caries is likely the cause of poor oral health. Comparatively, this situation is even worse in stroke patients . From the results above, dental caries plays an important negative role (OR = 1.292) in the abnormal oral cleanliness of acute ischemic stroke patients (Fig. 3).
Compared with the above risk variables, BI was the only protective factor in the two regression analyses (Fig. 3). It plays an important role in oral hygiene and SAP in patients with ischemic stroke, suggesting that we need to pay more attention to the rehabilitation of the ADLs of early diagnosed patients, which will help improve oral hygiene and SAP prevention.
ROC curve analysis suggested that the combination of SAP, dental caries, age and BI has enough discriminative power to distinguish oral hygiene in acute ischemic stroke patients; this power also exists in the efficiency of the combined BOAS score and BI in predicting SAP. The sensitivity and specificity of both models were satisfactory, with accuracy of 67.1% and 70.7%, respectively, in clinical practice.
Some limitations of this study should be noted: 1) a relatively small sample size of SAP patients was included in the present study; 2) to reduce the SAP diagnosis bias, case collection time should have been extended to the 7th day of the disease course; 3) patients with severe aphasia or tracheotomy were not included; and 4) biochemical indicators, such as inflammatory factors, were not included as potential risk factors. Therefore, an increase in the sample size and observational markers included can help to further analyze the mutual roles of oral hygiene and SAP in patients with acute stroke.