Compliance With Swallowing Instruction and Quality of Life in Patients With Parkinson's Disease: A Retrospective Assessment of Instructional Methods to Maintain and Improve Quality of Life

ABSTRACT

Objectives

To investigate the effects of swallowing instructional methods and content on instructional compliance among patients with Parkinson's disease (PD).

Methods

Overall, 59 of the 317 patients with PD who underwent a videofluoroscopic examination of swallowing (VF) and completed the Japanese version of the Dysphagia Handicap Index (DHI‐J) within 45 days before and after VF were analyzed. Based on records of compliance with alternative strategies from the time of instruction to 6 months, patients were classified into the compliance (CP) and noncompliance (NCP) groups.

Results

The NCP and CP groups included 31 (52.5%) and 28 (47.5%) patients, respectively. No significant differences in self‐reported severity or DHI score were identified, and quality of life (QOL) and awareness did not influence compliance. The CP group had more patients who received instruction using swallowing charts or handouts than the NCP group. More patients lived with family members. The NCP group had significantly higher DHI‐Physical (P) and DHI‐Total scores and lower QOL post‐instruction reassessment (Post) than pre‐instruction reassessment (Pre). Conversely, the CP group had significantly lower DHI‐P, DHI‐Emotional, and DHI‐Total scores and higher QOL in Post than in Pre.

Conclusions

When teaching swallowing with alternative strategies for dysphagia, using visual elements rather than verbal instructional elements alone is beneficial for improving compliance with instructional content. Compliance with swallowing instructions can maintain and improve QOL after the intervention. Patients living with family members demonstrated better compliance, likely due to meals provided by family members, along with advice and cooperation influencing compliance with the guidelines.

Summary

• Swallowing instructions using alternative strategies for managing dysphagia provided with a visual component rather than a verbal component alone is beneficial for compliance with instructional content in patients with Parkinson's disease.

• Intervention with swallowing instructions using various methods improves long‐term compliance and quality of life in patients with Parkinson's disease. Compliance was better in patients living with family members likely due to assistance in meal preparation along with advice and cooperation.

1. Introduction

Dysphagia affects quality of life (QOL) by causing difficulty in oral intake, weight loss, malnutrition, and restriction of social activities. It is a common feature of Parkinson's disease (PD). Although the reported prevalence rates vary, a recent meta‐analysis determined it to be 36.9%, and dysphagia is usually associated with severe clinical complications [1]. Medication is the first‐line treatment for PD; however, the evidence regarding its effectiveness for dysphagia is scarce [2]. The primary treatments for dysphagia in PD are categorized into functional training [3] and the use of alternative strategies [4]. Among these, alternative strategies are classified into texture‐modified diet (TMDs), thickened fluids, and postural adjustment, with reports highlighting their effectiveness in preventing aspiration pneumonia in patients [5]. However, patients with PD usually show noncompliance with alternative strategies due to a lack of awareness of their dysphagia [6].

The use of alternative strategies for managing dysphagia also affects QOL [7]. For example, while TMDs reduce the risk of aspiration and choking, the need for lifelong use of TMDs can be a burden to the patients, ultimately reducing their QOL [8]. Moreover, thickened fluids decline QOL, with thicker fluid resulting in a greater decline in QOL [9]. Because of the implications for QOL, some people may not comply with alternative strategies, even after being informed about the risks of pneumonia, complications, and death associated with dysphagia. Therefore, assessment and intervention of QOL associated with dysphagia are important in planning dysphagia management because QOL is related to continued compliance with alternative strategies for dysphagia [10].

This study aimed to implement an intervention focusing on alternative strategies for patients with PD and assess teaching methods, as well as their effectiveness, in promoting adherence to instructions from a QOL perspective.

2. Materials and Methods

2.1. Research Design

This was a retrospective cohort study that included patients with PD who were admitted to the hospital and underwent speech therapy between April 2016 and May 2021. PD was diagnosed in patients who met the Movement Disorder Society clinical diagnostic criteria [11], had a clinical diagnosis of clinically probable PD by a neurologist, and responded to anti‐parkinsonian treatment. None of the participants exhibited head magnetic resonance imaging findings suggestive of neurodegenerative diseases other than PD.

A total of 317 patients who had completed the Japanese version of the Dysphagia Handicap Index (DHI‐J) within 45 days before and after the videofluoroscopic swallow (VF) were included in this study. Patients with cerebrovascular complications or other diseases that could affect swallowing were excluded. In addition, patients with a Mini‐Mental State Examination (MMSE) score of < 23 points and those who had difficulty understanding the questionnaire were excluded. Overall, 159 patients with the absence of aspiration and/or pharyngeal residue on VF were excluded. We also excluded eight patients with slight aspiration, who were judged by the physician not to require swallowing instruction and 55 with slight pharyngeal residue. Finally, 59 of the 103 (57.3%) patients whose progress could be followed up were included in the analysis (Figure 1).

Figure 1.

Flowchart of participants' selection. DHI‐J, Japanese version of the Dysphagia Handicap Index; MMSE, Mini‐Mental State Examination; PD, Parkinson's disease; VF, videofluoroscopic examination of swallowing.

This study was approved by the National Center of Neurology and Psychiatry Ethics Committee (Approval number: A2020‐105; Date of approval: December 7, 2020). Patient backgrounds and data used were retrospectively extracted from clinical records; therefore, no new informed consent was obtained. Instead, the necessary information was published on the hospital's Ethics Committee website, and participants were allowed to decline participation.

2.2. Exposure

The exposure and outcome are indicated in Figure 2.

Figure 2.

Flowchart of study process. CP, compliance; DHI‐J, Japanese version of the Dysphagia Handicap Index; FOIS, Food Oral Intake Scale; NCP, noncompliance; PA, penetration‐aspiration; SDQ‐J, Japanese version Swallowing Disturbances Questionnaire; TMD, texture‐modified diet; VF, videofluoroscopic examination of swallowing.

2.2.1. VF

VF was performed on all participants, with individuals seated in the same position as during a meal. The assessment used a two‐fold diluted 110% (w/v) barium solution and 8 g of barium‐enriched corned beef. Next, the liquid was injected into the mouth using a syringe, and participants were instructed to swallow. Solids were placed in the participant's mouth with a splitter, and the participant was instructed to start chewing. Fluoroscopy was performed from the oral cavity to the upper esophagus, and swallowing movements were recorded at 30 frames per second on an external hard disk to assess the VF findings. Image analysis was conducted using EDIUS Pro 9® (Grass Valley, Montreal, Canada). For liquid swallowing, the presence or absence of aspiration was evaluated. In addition, the presence or absence of the cough reflex was considered using the Penetration‐Aspiration Scale (PA‐Scale) [12] for evaluation. The presence or absence of pharyngeal residuals was evaluated for solid food swallowing.

2.2.2. DHI‐J

The Related‐Swallowing QOL Questionnaire is commonly used to assess QOL [13], although the DHI used here was also a self‐reported QOL questionnaire [14]. Notably, the DHI‐J has been demonstrated to be reliable and valid [15]. It was administered at each hospital admission. The DHI‐J comprised 25 QOL‐related questions and items associated with perceived dysphagia; the QOL items included physical (P), functional (F), and emotional (E) aspects. Following previous studies, each item was answered as “never,” “sometimes,” or “always” and scored 0, 1, or 2 points, respectively. Scores for each aspect and the total score (DHI‐Total) were assessed [16]. The dysphagia perception items included an assessment of the subjective level of dysphagia, using a self‐reported severity score (SRSS) on a 7‐point scale (1, normal to 7, worst), as indicated by the patient.

2.2.3. Instruction Methods

Swallowing instruction was provided through the following three methods and instructional contents.

2.2.3.1. Oral Instruction

The VF results (presence or absence of aspiration, cough, and pharyngeal residue) were explained orally, and instructions on alternative strategies were also provided orally.

2.2.3.2. Instruction Using Visual Aids (Graph)

After explaining the VF results using a swallowing model diagram, instructions on alternative strategies were provided verbally.

2.2.3.3. Instruction with Handouts (Handouts)

Instructions on alternative strategies were provided after explaining the VF results using a handout and ticking the relevant items.

2.2.4. Instruction Contents

Typically, alternative strategies for managing dysphagia can be classified as TMDs, thickened fluids, and postural adjustments [5]. Based on the results of the VF, instruction on alternative strategies was selected from the three options after consultation with a neurologist, as deemed appropriate. Instruction on alternative strategies was provided where necessary.

2.2.4.1. TMDs

Although meal forms are classified according to the Food Oral Intake Scale (FOIS) [17], TMDs are adjusted for masticatory capacity and texture according to the International Dysphagia Dietary Standards Initiative (IDDSI) framework [18]. In this study, the texture was modified according to the Japanese Dysphagia Diet 2021 (JDD 2021) of the Japanese Society for Swallowing Rehabilitation Dysphagia Diet Committee [19].

2.2.4.2. Thickened Fluids

The thickening concentration was defined according to the IDDSI framework and TMD. The consistency of the thickened liquids was graded according to the patient's swallowing ability, but in this study, regardless of whether a thickening agent was used, the patients were classified according to whether they had dysphagia. Since the study purpose was not to analyze whether the use of a thickening agent prevented aspiration, the consistency of the thickened liquids was not considered in the statistical analysis.

2.2.4.3. Postural Adjustments

The chin‐down posture can reduce the risk of pharyngeal remnants and aspiration [20]. This study instructed patients with appropriate postural adjustments to maintain a chin‐down posture.

2.3. Outcome

2.3.1. Exposure Factors to be Considered in Compliance With Swallowing Instructions

The author and/or three speech‐language pathologists reviewed records of the implemented alternative strategies within 6 months of providing swallowing instruction. Patients were classified as the “compliance group” (CP group) if they self‐reported at the subsequent outpatient visit or admission following any swallowing‐instructed strategies at home. When multiple instructions were provided, the patients were included in the CP group if they adhered to one of the instructions. If none of the swallowing instructions were complied with, the patients were classified as the “noncompliance group” (NCP group). We also compared the CP and NCP groups by instructional methods.

2.3.2. Considering the Effects of Swallowing Instructions

Patients who had received swallowing instructions and were subsequently hospitalized within 6 months of the instructions were reassessed using the DHI‐J. We compared the before and after results for the CP and NCP groups.

2.4. Statistical Analysis

2.4.1. Exposure Factors to be Considered in Compliance With Swallowing Instructions

The CP and NCP groups were compared using the Mann–Whitney U test. Significant differences (p) and statistics (U) were measured, with p < 0.05 considered statistically significant. Furthermore, the Bonferroni method accounted for statistical repetitions, with p < 0.016 considered statistically significant.

2.4.2. Considering the Effects of Swallowing Instructions

The DHI‐J items were compared between the CP and NCP groups at the pre‐instruction reassessment (Pre) and post‐instruction reassessment (Post) using the Wilcoxon signed‐rank test. Significant differences (p) and statistics (Z) were measured, with a significance level set at p < 0.05. All statistical analyses were performed using IBM SPSS Statistics for Windows, version 25 (IBM Corp., Armonk, NY, USA).

3. Results

3.1. Exposure Factors to be Considered in Compliance With Swallowing Instructions

3.1.1. Comparison of CP Group versus NCP Group

Overall, 31 (52.5%) and 28 (47.5%) patients were in the NCP and CP groups, respectively (Table 1), with no significant differences in DHI scores. QOL was unaffected by compliance. In the case of oral instruction, the instructions were not complied with significantly. However, they were complied with using graphs and handouts. Patients living with family members were also more likely to comply with the instructions than those living alone.

Table 1.

Comparison of CP group versus NCP group.

Items	NCP (n = 31)	CP (n = 28)	Z	p‐value
Background
Sex (male:female)	23:8	18:10	−0.818	0.413
Age (years)	73.0 [68.0–79.5]	72.5 [69.0–76.0]	−1.096	0.273
Duration (n = 52)	10.0 [6.5–15.0]	10.0 [7.0–14.0]	−0.275	0.783
H & Y (n = 52)	3.0 [3.0–3.6]	3.0 [2.9–4.0]	−0.039	0.969
UPDRS (n = 50)	61.5 [44.3–85.8]	50.5 [32.8–77.5]	−1.350	0.177
MMSE	27.0 [25.3–29.8]	27.0 [25.0–29.3]	−0.049	0.961
Meal
TMDs	8	6	−0.196	0.845
Thickness	4	7	−1.553	0.144
VF findings
Aspiration	15	18	−1.460	0.224
Silent aspiration	10	15	−1.125	0.224
Residue	24	25	−1.203	0.229
PA‐scale	2.0 [1.0–8.0]	8.0 [2.0–8.0]	−1.363	0.173
FOIS
Hospitalization	7.0 [4.5–7.0]	7.0 [5.0–7.0]	−0.500	0.617
Discharge	5.0 [4.0–7.0]	5.0 [4.0–7.0]	−0.922	0.357
DHI
P	4.0 [2.0–6.0]	6.0 [3.8–8.0]	−1.366	0.172
F	2.0 [0.0–5.0]	3.0 [2.0–6.3]	−0.943	0.346
E	2.0 [0.0–5.5]	4.0 [1.0–6.0]	−1.142	0.253
Total	8.0 [4.0–17.5]	12.5 [7.8–22.3]	−1.452	0.147
SRSS	2.0 [1.5–4.0]	4.0 [2.8–5.0]	306.5	0.048*
SDQ‐J	12	14	−1.268	0.205
Instruction methods
Oral	24	6	−4.259	< 0.001**
Graph	2	7	−1.962	0.050*
Handouts	5	18	−3.755	< 0.001**
Family living together	24	27	−2.112	0.035*

Abbreviations: CP, compliance; DHI, Dysphagia Handicap Index; E, emotional; F, functional; FOIS, Food Oral Intake Scale; H & Y, Hoehn & Yahr stage; MMSE, Mini‐Mental State Examination; NCP, noncompliance; P, physical; PA, penetration‐aspiration; SDQ‐J, Japanese version Swallowing Disturbances Questionnaire; SRSS, self‐reported severity score; TMD, texture‐modified diet; UPDRS, Unified Parkinson's Disease Rating Scale; VF, videofluoroscopic examination of swallowing.

^* p < 0.05

^** p < 0.01.

3.1.2. Comparison of CP and NCP Groups by Instruction Contents

3.1.2.1. TMDs

Seventeen 17 (68.0%) and 8 (32.0%) patients were in the NCP and CP groups, respectively (Table 2). No significant difference was observed in DHI scores. QOL was unaffected by compliance. Patients who were aware of their dysphagia followed instructions. Those who followed TMD instructions also followed instructions on thickened fluids and postural adjustments. Oral instructions were not significantly followed. In contrast, instructions were followed when using handouts. The use of graphs did not affect compliance with instructions.

Table 2.

Comparison of CP group versus NCP group by instruction contents (TMDs).

Items	NCP (n = 17)	CP (n = 8)	Z	p‐value
Background
Sex (Male:Female)	10:7	5:3	−0.171	0.864
Age (years)	73.0 [70.0–80.0]	73.0 [68.0–77.0]	0.000	1.000
Duration	10.5 [7.5–15.0]	12.0 [6.0–20.5]	−0.216	0.829
H & Y	3.0 [3.0–4.0]	3.5 [2.6–4.0]	−0.163	0.871
UPDRS	80.0 [45.0–90.0]	51.5 [46.3–74.8]	−0.483	0.629
MMSE	28.0 [26.0–30.0]	26.5 [25.3–27.8]	−0.666	0.505
Meal
TMDs	7	4	−0669	0.503
Thickness	3	1	−0.052	0.959
VF findings
Aspiration	6	4	−0.980	0.327
Silent aspiration	3	3	−0.477	0.655
Residue	16	6	−0.825	0.409
PA‐Scale	2.0 [1.0–6.0]	4.0 [1.8–8.0]	−0.979	0.327
FOIS
Hospitalization	7.0 [4.0–7.0]	5.5 [4.0–7.0]	−0.265	0.791
Discharge	4.0 [4.0–4.0]	4.0 [4.0–4.0]	−0.557	0.577
DHI
P	4.0 [2.0–6.0]	5.0 [2.0–8.3]	−0.294	0.769
F	3.0 [0.0–4.0]	3.5 [1.8–8.0]	−0.980	0.327
E	2.0 [0.0–4.0]	3.0 [1.8–5.8]	−0.826	0.409
Total	8.0 [3.0–14.0]	12.5 [7.0–22.3]	−0.846	0.398
SRSS	2.0 [1.0–4.0]	4.5 [3.0–5.0]	−1.797	0.072
SDQ‐J	8	5	−0.786	0.432
Instruction contents
TMDs	—	—	—	—
Thickened fluids	2/5	5/5	−2.182	0.029*
Postural adjustments	2/8	5/6	−2.082	0.037*
Instruction methods
Oral	12	1	−2.657	0.008**
Graph	3	2	−0.420	0.674
Handouts	2	5	−2.582	0.010*
Family living together	13	8	−1.467	0.142

Abbreviations: CP, compliance; DHI, Dysphagia Handicap Index; E, emotional; F, functional; FOIS, Food Oral Intake Scale; H & Y, Hoehn & Yahr stage; MMSE, Mini‐Mental State Examination; NCP, noncompliance; P, physical; PA, penetration‐aspiration; SDQ‐J, Japanese version Swallowing Disturbances Questionnaire; SRSS, self‐reported severity score; TMD, texture‐modified diet; UPDRS, Unified Parkinson's Disease Rating Scale; VF, videofluoroscopic examination of swallowing.

^* p < 0.05

^** p < 0.01, — no data.

3.1.2.2. Thickened Fluids

The number of patients in the NCP and CP groups was 12 (46.2%) and 14 (53.8%), respectively (Table 3). No significant difference was observed in DHI scores, and QOL did not affect compliance with instructions. Patients who complied with thickened fluids instructions also complied with TMD instructions. Significant compliance was observed with instructions using handouts.

Table 3.

Comparison of CP group versus NCP group by instruction contents (thickened fluids).

Items	NCP (n = 12)	CP (n = 14)	Z	p‐value
Background
Sex (Male:Female)	6:6	8:6	−0.772	0.440
Age (years)	74.0 [71.3–78.0]	75.0 [70.5–77.0]	−0.592	0.554
Duration	11.0 [8.0–12.0]	9.0 [7.0–15.5]	−0.216	0.829
H & Y	3.0 [2.5–3.0]	3.5 [2.8–4.0]	−1.055	0.291
UPDRS	46.0 [37.0–76.0]	53.0 [47.5–85.0]	−1.018	0.308
MMSE	26.0 [24.0–27.5]	28.0 [26.0–29.0]	−1.392	0.164
Meal
TMDs	2	4	−0.704	0.481
Thickness	7	2	−1.746	0.081
VF findings
Aspiration	1	12	0.000	1.000
Silent aspiration	7	10	−1.950	0.051
Residue	9	14	−1.491	0.136
PA scale	8.0 [6.0–8.0]	8.0 [8.0–8.0]	−0.885	0.376
FOIS
Hospitalization	7.0 [6.5–7.0]	5.0 [4.3–7.0]	−1.447	0.148
Discharge	5.0 [4.0–5.0]	5.0 [4.0–5.0]	−0.125	0.901
DHI
P	4.5 [2.8–8.0]	6.5 [5.3–8.8]	−1.526	0.127
F	3.0 [2.0–6.3]	4.5 [3.3–7.8]	−1.087	0.277
E	2.5 [0.0–5.3]	5.0 [2.3–7.5]	−1.451	0.147
Total	9.5 [7.0–17.3]	16.6 [12.3–22.8]	−1.519	0.129
SRSS	2.5 [2.0–4.0]	4.0 [3.0–5.0]	−1.380	0.168
SDQ‐J	5	6	−0.603	0.546
Instruction contents
TMDs	0/4	5/7	−2.182	0.029*
Thickened fluids	—	—	—	—
Postural adjustments	2/7	6/9	−1.464	0.143
Instruction methods
Oral	4	8	−1.905	0.057
Graph	2	4	−0.704	0.481
Handouts	2	8	−2.074	0.038*
Family living together	11	14	−1.080	0.280

Abbreviations: CP, compliance; DHI, Dysphagia Handicap Index; E, emotional; F, functional; FOIS, Food Oral Intake Scale; H & Y, Hoehn & Yahr stage; MMSE, Mini‐Mental State Examination; NCP, noncompliance; P, physical; PA, penetration‐aspiration; SDQ‐J, Japanese version Swallowing Disturbances Questionnaire; SRSS, self‐reported severity score; TMD, texture‐modified diet; UPDRS, Unified Parkinson's Disease Rating Scale; VF, videofluoroscopic examination of swallowing.

^* p < 0.05

^** p < 0.01, — no data.

3.1.2.3. Postural Adjustments

The number of patients in the NCP and CP groups was 22 (52.3%) and 20 (47.7%), respectively (Table 4). No significant difference was observed in DHI scores, and QOL did not affect compliance with instruction. Patients who were compliant with postural adjustment instructions were also compliant with TMD instructions. Instruction was significantly more compliant when using handouts but not compliant with oral instruction alone.

Table 4.

Comparison of CP group versus NCP group by instruction contents (postural adjustments).

Items	NCP (n = 22)	CP (n = 20)	Z	p‐value
Background
Sex (Male:Female)	18:4	13:7	−1.123	0.221
Age (years)	73.0 [69.3–76.0]	71.5 [68.5–73.8]	−1.086	0.277
Duration	9.0 [6.5–16.0]	11.0 [7.5–14.0]	−0.512	0.609
H & Y	3.0 [3.0–4.0]	3.0 [2.6–3.8]	−0.660	0.509
UPDRS	62.5 [44.5–93.3]	34.0 [31.5–78.5]	−1.763	0.078
MMSE	26.0 [25.0–29.0]	27.0 [25.0–29.5]	−0.416	0.677
Meal
TMDs	5	2	−0.543	0.587
Thickness	3	4	−0.744	0.457
VF findings
Aspiration	12	12	−0.352	0.724
Silent aspiration	10	9	0.000	1.000
Residue	17	18	−1.092	0.275
PA scale	6.0 [1.0–8.0]	6.0 [2.0–8.0]	−0.375	0.708
FOIS
Hospitalization	7.0 [5.5–7.0]	7.0 [5.0–7.0]	−0.095	0.924
Discharge	5.0 [4.0–7.0]	5.0 [4.0–7.0]	−0.229	0.819
DHI
P	4.0 [2.0–5.8]	6.0 [3.5–8.3]	−1.356	0.175
F	3.0 [1.3–5.0]	3.0 [1.0–5.8]	−0.165	0.889
E	2.0 [0.3–5.0]	4.0 [0.8–6.5]	−0.969	0.319
Total	8.5 [7.0–17.3]	13.0 [4.8–23.0]	−0.997	0.319
SRSS	2.0 [2.0–3.8]	4.0 [2.5–5.0]	−1.884	0.060
SDQ‐J	7	11	−1.646	0.100
Instruction contents
TMDs	1/6	5/7	−2.082	0.037*
Thickened fluids	3/8	6/8	−1.464	0.143
Postural adjustments	—	—	—	—
Instruction methods
Oral	16	2	−4.054	< 0.001**
Graph	0	5	−1.869	0.062
Handouts	6	13	−2.442	0.015*
Family living together	18	19	−1.302	0.193

Abbreviations: CP, compliance; DHI, Dysphagia Handicap Index; E, emotional; F, functional; FOIS, Food Oral Intake Scale; H & Y, Hoehn & Yahr stage; MMSE, Mini‐Mental State Examination; NCP, noncompliance; P, physical; PA, penetration‐aspiration; SDQ‐J, Japanese version Swallowing Disturbances Questionnaire; SRSS, self‐reported severity score; TMD, texture‐modified diet; UPDRS, Unified Parkinson's Disease Rating Scale; VF, videofluoroscopic examination of swallowing.

^* p < 0.05

^** p < 0.01, — no data.

3.2. Consideration of the Effects of Swallowing Instructions

As shown in Figure 3, 20 (33.9%) patients could perform the DHI‐J again after receiving swallowing instructions. Nine (45.0%) and 11 (55.0%) patients were in the NCP and CP groups, respectively. No significant difference was found between the CP and NCP groups for Pre or Post across all items. Comparing Pre and Post, no significant difference in SRSS was found between the CP and NCP groups. The NCP group had significantly higher DHI‐P (p = 0.042, Z = −2.035) and DHI‐Total (p = 0.050, Z = −1.960) scores and lower QOL Post than Pre. Nevertheless, the CP group had significantly lower DHI‐P (p = 0.032, Z = −2.140), DHI‐E (p = 0.011, Z = −2.536), and DHI‐Total (p = 0.011, Z = −2.556) scores and higher QOL Post than Pre.

Figure 3.

Effects of swallowing instructions in patients with Parkinson's disease. CP, compliance; DHI, Dysphagia Handicap Index; DHI‐E, Dysphagia Handicap Index‐Emotional; DHI‐F, Dysphagia Handicap Index‐Functional; DHI‐P, Dysphagia Handicap Index‐Physical; Pre, pre‐instruction reassessment; Post, post‐instruction reassessment; n.s., not significant; NCP, noncompliance; SRSS, self‐reported severity score. *p < 0.05.

4. Discussion

4.1. Instruction Contents

4.1.1. TMDs

TMDs are suitable for training to maintain and improve swallowing ability and effectively prevent recurrent pneumonia, as they promote safe food intake and allow active direct swallowing training [21]. In this study, 14 out of 25 patients (56.0%) who required TMD were consuming regular food, which is consistent with findings of previous reports indicating that TMD may not be provided to patients with dysphagia that is appropriate for their swallowing ability [22]. Regarding solid foods, chewed food is delivered to the oropharynx before the swallowing reflex is initiated by active transport from the tongue (Phase II transport). Solid foods are more sensitive to sensory feedback from chewing and the oropharynx. In this study, patients who were aware of dysphagia were better at following instructions and were more likely to follow TMD instructions. Therefore, the participants were less likely to follow TMD instructions if they were unaware of dysphagia. In addition, the consumption of regular foods may have been influenced by the fact that TMDs are more expensive than regular meals, as they require extensive cooking processes, thickening agents, and special cooking equipment [19].

4.1.2. Thickened Fluids

Thickened fluids reduce the risks of laryngeal penetration and aspiration [23]. However, two‐thirds of patients do not comply with expert recommendations [24]. In this study, the compliance rate was 53.8%, higher than that previously reported, whereas almost half of the patients did not comply. Several psychological factors are considered to contribute to noncompliance with the instructions [25]. Patients were not significantly aware of aspiration, which was also considered a contributing factor to noncompliance. PD symptoms may affect the cortical swallowing network [26], which could be related to the perception of dysphagia, as it is affected by the regulation of bite size and the control of intake rate [27]. Other contributing factors include difficulty adapting to alternative strategies for thickening liquids [28] and a lack of knowledge about dysphagia treatment [29].

In this study, dysphagia awareness was not significantly related to compliance with instructions on thickened fluids. Based on the above findings, the lack of awareness about the need to adjust the liquid viscosity and the difficulty in adapting to the adjusted liquid viscosity could have contributed to the observed compliance.

4.1.3. Postural Adjustments

The chin‐down posture alters the volume and shape of the pharynx, facilitating laryngeal vestibular closure during swallowing [30] and reducing the risk of aspiration [31]. The chin‐down posture was reported to successfully eliminate aspiration in one out of three patients with PD [32]. Here, despite the highest number of participants receiving swallowing instructions on this posture, the compliance rate was 47.6%, similar to that of the other swallowing instructions. Awareness of aspiration influenced postural adjustment, as well as other instructions. Stiffening of the cervical muscles in patients with PD also makes it challenging for them to adopt a chin‐down posture [33], and they may encounter difficulty performing the posture correctly even after receiving instructions.

4.2. Instruction Methods

Feeding and swallowing rehabilitation was conducted according to the principles of motor learning [34], and accurate feedback is essential for successful motor learning [35]. Feedback can be categorized as internal, external, or mixed. Verbal feedback encompasses verbal cues or instructions, whereas visual feedback refers to external visual sources of information. Swallowing movements occur in the closed space of the oropharynx, limiting internal feedback [36]. Therefore, external feedback facilitates the motor learning of swallowing movements [37].

The results showed that the groups receiving visual feedback with the graph and receiving combined feedback with handouts were more compliant with the swallowing instructions than the group receiving verbal feedback with oral instruction, and their QOL was maintained at the time of reassessment.

Combined feedback is more effective than verbal feedback alone because it can optimize motor learning in the presence of cognitive impairment by deliberately directing attention outward in addition to verbal feedback [38]. Functional training with visual feedback has also been reported to improve QOL [39]. The results of this study are comparable with those of previous studies, suggesting that complex feedback is effective not only in functional training but also in teaching swallowing using alternative strategies. However, how the different types of feedback affect motor learning [40] and the difference between the effects of verbal and visual feedback remains unclear [41]. In this study, no significant difference in compliance with swallowing instructions was observed even when graph‐based visual feedback was provided for instruction on thickened fluids and postural adjustments, suggesting the need for further investigation into more effective instruction methods.

4.3. Considering the Effects of Swallowing Instructions

Dysphagia affects QOL by causing difficulties in oral intake, weight loss, malnutrition, and limitations in social activities [42]. In this study, there was no significant difference in DHI scores between the CP and NCP groups, and it is possible that QOL was not related to compliance with swallowing instructions.

The discrepancy in QOL according to the VF results may be attributed to the fact that 14 (23.7%) patients in this study had already implemented TMDs, 11 (18.6%) had already implemented thickened fluids before receiving swallowing instruction, and their QOL may have already been reduced regardless of their compliance with the instruction. The QOL questionnaire also indicated that awareness of dysphagia had an impact [13], and a lack of awareness of dysphagia was believed to influence QOL. In contrast, QOL was better maintained and improved when patients could follow swallowing instructions.

This study shows that teaching alternative strategies for managing dysphagia can maintain long‐term QOL. Since no significant difference in the SRSS was observed between assessment and reassessment, the effect was possibly due to the instruction alone and not subjective compliance symptoms. A reduction in the incidence of pneumonia and mortality, as well as the length of hospital stay, was observed when swallowing instructions were provided [43]. The CP group complied with the postural adjustments taught, which probably influenced the maintenance and improvement of the physical and emotional aspects of QOL, as the frequency of aspiration and associated pneumonia was reduced.

4.4. Limitations

This study has some limitations. First, the participants were individuals with MMSE scores of ≥ 24. Dementia prevalence is 30% in patients with PD, which is six times higher than in healthy participants [44]. Attention and other factors associated with cognitive impairment also influence feedback [45]. Therefore, future studies should consider comprehension and attention to swallowing instructions.

Second, all study participants consumed food orally; however, the selection criteria did not include whether TMDs or thickened liquids had been adjusted before swallowing instruction. Although masticatory disorders affect swallowing and nutritional status [5], dental status was not assessed in this study. In addition, dysphagia severity and the reasons for implementing alternative strategies may have differed. Therefore, re‐examining QOL by adjusting for dysphagia severity using the FOIS is necessary in the future.

Third, swallowing instruction in this study was only provided immediately before discharge, and whether swallowing skills training was given during hospitalization or instruction status after discharge with third‐party follow‐up was not considered. Compliance after instruction was also assessed at the time of confirmation within 6 months, and the range of periods was large. Varying the timing and frequency of feedback can influence motor learning [46]. Because this study was retrospective, standardizing the implementation of these conditions was difficult. Therefore, future prospective studies should consider the timing of instruction, compliance checks, and the methods of instruction.

5. Conclusions

This study indicates that providing instructions using alternative strategies for managing dysphagia with a visual component rather than a verbal component alone is useful for compliance with instructional content. Compliance with swallowing instructions can maintain and improve QOL after the intervention. This finding suggests that interventions improve long‐term compliance with instructional content using various methods.

Author Contributions

Keigo Nakayama: conceptualization, methodology, investigation, writing–original draft preparation, funding acquisition, resources. Toshiyuki Yamamoto: writing–review and editing, resources. Takatoshi Hara: writing – review and editing. Yuji Takahashi: writing–review and editing. Takeshi Murakami: writing – review and editing. Hajime Sano: writing–review and editing, funding acquisition. Daisuke Nishida: writing–review and editing, supervision.

Ethics Statement

This study was approved by the National Center of Neurology and Psychiatry Ethics Committee (approval number: A2020‐105, date of approval: December 7, 2020).

Consent

Patient background information and data used in this study were retrospectively extracted from clinical records; hence, no new informed consent was obtained. Instead, the necessary information was published on the hospital's ethics committee website, and participants were allowed to decline participation.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available owing to restrictions, e.g., they contain information that could compromise the privacy of research participants.