4.1. Generalizability from the demographic data
This study represents several factors of self-efficacy that affect the swallowing function. The prevalence of malnutrition in Europe and North America is 1–15% among non-institutionalized older adults, 25–60% among older adults in geriatric care facilities, and 35–65% among older adults in hospitals, and our sample presented the same level of prevalence (43.3%) . Additionally, Frowen et al. reported similar characteristics (male: 49%; mean age: 59 years; tumor type: 20.5% hematology, 18.4% breast, 11.3% head and neck, 10% Gynecology, 8.8% upper gastrointestinal, 8.8% colorectal, 8.4% skin/melanoma, 4.6% bone soft tissue, 3.8% lung, 5.4% other; patient setting: 21.3% inpatient, 56.1% chemotherapy, 22.6% radiotherapy) and prevalence of patient-reported dysphagia (54%) . However, most patients in the present sample had solid cancer and the most common treatment type was surgery, which may lead to a low prevalence of dysphagia as compared to that observed in the previous study. With reference to oral health status, previous studies reported that the prevalence of denture use was 15.9% (57.4% in our study), and that of dental visit(s) in the last 12 months was 52.1% (41.1% in our study) [28, 29]. The number of teeth reported in our study was lesser than that reported in other studies, which may affect OSEC and FOIS scores. Globally, we may be the first to report the FOIS score of general cancer patients; however, those with head and neck cancer tended to exhibit poor FOIS scores, which was consistent with the findings of previous studies [30, 31]. The study by Hirai et al. on self-efficacy (SEAC) in patients with advanced cancer showed similar results (ARE: 57.7–84.8, SCE: 53.6–61.2, ADE: 64.8–72.9). Thus, the generalizability of the present study was limited to patients with early-stage cancer undergoing initial treatment.
4.2. Comparison of the High and Low FOIS groups by swallowing function
The factors influencing swallowing functions were age, sex, BMI > 30, smoking status, alcohol use, cognitive factors (depression, anxiety, and psychological distress), eating habits (loss of appetite, mouth pain, complaints about the taste of the food, intake of dietary supplements, and ability to eat independently), medical factors (vision or hearing problems, constipation, heart failure, hip fracture, stroke, dementia, Parkinson’s disease, weight loss, frailty and number of medications taken in the past week, physical limitations, toxic habits, and cancer), social factors (highest level of education, income satisfaction, type of housing, number of cohabitants, and perceived satisfaction with social support) and dental status [32–37]. The factors reported in the present study have also been reported by previous studies, thus, our results on comparisons between high and low FOIS groups were not contradicted. Notably, there were significant differences between the high and low FOIS groups’ scores on the SEAC (ARE, ADE, and total score) and OSEC (OFE and total score). These may be new findings on self-efficacy-related factors that influence swallowing functions. Self-efficacy expectations are positively and significantly associated with the initiation and maintenance of healthy behaviors [38, 39]. Thus, self-efficacy may determine the ability of cancer patients to eat or select appropriate food. Moreover, these abilities may influence the probability of weight loss, appetite loss, and recurrence of cancer . The multivariate analysis conducted in the present study revealed factors associated with the FOIS category (number of co-residents, cancer type and stage, performance status, number of teeth, family dentist, and ADE and SCE scores on the SEAC). However, contrary to our expectations, OSEC scores were not associated with the swallowing function. According to Bandura, the development of self-efficacy related to an activity is based upon past successful experiences with that specific behavior . Therefore, patients who experience these swallowing disorders after the deterioration of their ability to perform activities of daily living may have difficulty in drawing from past successful experiences, thus reducing their confidence in performing the swallowing function. In other words, there may be an underlying interaction between swallowing function and OSEC scores.
4.3. Trends in FOIS scores and self-efficacy
In the sub-group analysis, all subscales of the SEAC, and the OFE and total score on the OSEC showed a stepwise increase in FOIS score. Thus, self-efficacy showed a stepwise correlation with the FOIS score. More attention should be paid to the provision of care and coaching focused on defusing negative emotional experiences in each stage of dysphagia and self-efficacy. Our previous report showed the stepwise correlation between the HRQoL and FOIS score . Therefore, such interventions may enhance the patient’s confidence in their swallowing abilities.
4.4. Intervention for cancer patients suffering from swallowing dysfunction
Oral care containing rehabilitation of dysphagia and oral function, whether self-performed or performed by dentists and dental hygienists, is fundamental to the prevention of some adverse events (postoperative pneumonia, chemoradiotherapy-induced oral mucositis, taste disturbance, infection of the oral cavity, and swallowing disorder). Dysphagia is widely recognized as a common and debilitating side-effect of head and neck cancer (HNC) and its treatment; however, minimal attention has been given to dysphagia in patients with other types of cancer . A review highlighted several methods of rehabilitation for dysphagia in head and neck cancer, and their effectiveness was evidenced by a randomized control trial . However, most of the rehabilitation efforts for head and neck cancer patients with dysphagia focus on the pathophysiology of dysphagia, including objective assessment (videoendoscopic evaluation of swallowing, videofluoroscopic examination of swallowing, dysphagia severity scale, and the FOIS) . However, a psychosocial approach should be emphasized for cancer patients with dysphagia. The food judged by the medical staff as edible is not the same as what the patients can or want to eat. In a prospective cohort study of 100 patients with either transient ischemic attack or ischemic stroke, Brouwer et al. found that baseline self-efficacy, as determined by patients’ responses on questionnaires, was the strongest predictor of his/her intention to adopt a healthy diet (95% CI, 0.23–0.75). Thus, based on the aforementioned studies, it may be beneficial for hospitals’ neurosurgery and neurology departments to coordinate long-term stroke coaching programs and assess patients’ behavioral patterns to increase patients’ adherence to healthy lifestyles. On the other hand, in patients with head and neck cancer, Roganie et al. reviewed only 15 (8 randomized) behavior change technique (BCT) reports, and they reported that BCTs used more frequently in effective interventions were: practical social support; behavioral practice; self-monitoring of behavior; and credible source, for example, a skilled clinician delivering the intervention. As a result, swallowing interventions feature multiple components that may potentially impact outcomes . These BCTs may improve the discrepancy of objective and subjective dysphagia.
This study had some limitations. First, our study design was cross-sectional; therefore we could not determine the causal relationship between dysphagia and self-efficacy. Particularly, we observed the stepwise tendency between self-efficacy and FOIS; however, it was evaluated only at a specific instance. Thus, a future study should verify the stepwise relationship between self-efficacy and FOIS using a longitudinal design. Second, the participants who visited the oral care center had good oral health-related knowledge and attitudes; therefore, it is likely that they represented a higher oral health related-self-efficacy. Therefore, selection bias might exist. Although we consider that observational studies cannot avoid such selection bias, we believe that our findings provide important suggestions for randomized controlled trials in the future, which would reveal the actual impact of self-efficacy.