Some previous studies have suggested that oral care prevents pneumonia in older patients, with a relative risk of pneumonia of 19% and 11% in older patients with poor and good oral health, respectively. In addition, previous studies have reported that older patients with poor oral health have a 1.7-fold higher relative risk of pneumonia compared to those with good oral health [1]. Past reports also suggest that the cough reflex threshold was significantly reduced after 1 month of meticulous oral care in a nursing home for older adults, compared to that before the start of care [2]. Furthermore, individuals receiving oral care from a dental hygienist twice a week for 24 months in nursing homes had a significantly lower likelihood of fever and deaths from aspiration pneumonia compared to individuals who did not receive oral care [3]. Therefore, oral care is recommended as part of the treatment of dysphagia, especially in older residents of nursing homes.
Although the oral environment significantly affects the risk of pneumonia, few studies have evaluated its relationship with swallowing. There is no doubt that there is a significant link between the oral environment and the development of pneumonia; however, there are few reports comparing VE and VF as indicators to determine the actual availability of oral intake and the choice of food form.
Nakayama et al. [9] studied patients admitted to a convalescent hospital and found that the Functional Oral Intake Scale (FOIS) score was significantly associated with saliva and denture scores. However, after excluding patients on non-oral nutrition, no significant association between FOIS and OHAT scores was observed. Importantly, the FOIS score reflects oral intake status rather than swallowing function.
VE is a comparable procedure to VF[10], recent studies using the Hyodo scoring system have shown that VE is simple to perform and effective for predicting aspiration, with a score of ≥ 6 corresponding to the highest risk of aspiration [11]. The Hyodo score significantly correlates with handgrip strength and peak expiratory flow rate, making it useful for examining the effects of strength training on dysphagia [12].
VF is the most reliable swallowing assessment method because it can evaluate the oral, pharyngeal, and esophageal phases [13]. In addition, VF is extremely useful when making policy decisions, and whiteout due to pharyngeal contraction does not occur. At our institution, VF is also used to determine the timing of a return to oral intake after prolonged fasting and the optimal treatment for swallowing rehabilitation or surgery to improve swallowing.
In the present study, we did not identify any correlations between the OHAT score for oral assessment and VE and VF scores for swallowing. In addition, the OHAT score did not differ between the no- or single-pneumonia episode and multiple-pneumonia episode groups, while the rates of swallowing endoscopy and angiography differed significantly between the groups. In our previous study [9], we identified significant differences in the oral and pharyngeal phases on VE between older patients with pneumonia and those without a history of pneumonia; notably, we observed a significant group difference in the elicitation of the gag reflex. These findings suggest that for patients with fever, difficulty in oral intake, or with other findings suggestive of dysphagia, VE or VF for the evaluation of swallowing, in addition to oral assessment, is necessary. This suggests that pneumonia in older adults is more likely when both poor oral health and poor pharyngeal swallowing function are present; however, we speculate that poor pharyngeal swallowing function is the dominant factor.
The present study is limited, as it is not a simple comparison of patients with and without a history of aspiration pneumonia. Additionally, there were no cases with extremely poor oral health, as the study participants were inpatients and some nursing care was provided. Thus, the number of cases was small, and the underlying disease background was varied.
Age-related swallowing dysfunction is multifactorial, with 63% of older patients (mean age: 83 years) having oral abnormalities, such as difficulty ingesting, controlling, or delivering a bolus to initiate swallowing; this prevalence rate was higher compared to young patients without dysphagia. In addition, 25% of older patients have pharyngeal dysfunction, such as bolus retention and tongue propulsion or pharyngeal muscle paralysis, and 36% have esophageal abnormalities due to cricopharyngeal muscle dysfunction [14]. Age-related swallowing dysfunctions in older adults without organic diseases, such as stroke, cancer, or dementia, include a prolonged oral transit time and aspiration [15].
In the present study, the multiple-pneumonia episodes group had higher VE and VF scores for all items, compared with the no- or single-pneumonia episode group. Thus, the group with repeated pneumonia, despite having a good oral environment, was likely to be experiencing several issues, including those associated with clearing of the pharynx and delayed induction of the swallowing reflex, as indicated by VE and VF results.