A systematic review of behavioural therapies for improving swallow and cough function in Parkinson’s disease

Figures & data

Table I. Selection criteria of the studies included in this review.

Selection criteria	Inclusion criteria	Exclusion criteria
Participants	Adults with idiopathic PD All stages and levels of PD severity All severity levels of swallowing difficulties or without swallowing problems	Other Parkinsonian syndromes and neurological disorders
Study design	Randomised controlled trials, quasi-randomised controlled trials, case-control studies, prospective cohort studies, and comparative observational studies	Single case report, single-session study, repeated published studies, secondary data (reviews)
Study setting	Any setting (hospital, rehabilitation unit, and residence)
Intervention	Any behavioural therapy trials that report a swallow or respiratory/cough outcome in individuals with PD	Pharmacological and surgical treatments Compensatory strategies and single-session treatment design
Comparator	None or sham/placebo treatment, drug/surgical treatment, or other swallow rehabilitation
Outcomes	Quantitative or qualitative Outcomes in objective and/or subjective measures of swallow, respiration, and cough function	Studies without pre- and post-intervention data
Publication details	Peer-reviewed articles Articles in English	Book chapters, thesis publications, editorials, commentaries

Figure 1. Adapted PRISMA flow diagram, presenting different phases of study selection for the systematic review.

Table II. Types of interventions and outcomes.

Intervention	Objective/ instrumental swallow measures	Objective cough/respiratory measures	Change in quality of life	Functional swallow outcome (or change in events of aspiration, secretion, residue severity)	Adverse effects (%)
Swallow-related therapies
Effortful swallow + tongue exercises (Wang et al., 2018)	√
Tongue isometric pressure exercises + traditional tongue training therapy (Plaza & Ruviaro Busanello-Stella, 2022)	√		√
Motor swallow exercise (vocal exercises + tongue hold + supraglottic swallow + swallow muscle range of movements; Argolo et al., 2013)	√		√	√
Video assisted swallow training (Manor et al., 2013)	√		√	√
Biofeedback in strength and skill training (Athukorala et al., 2014)	√^d		√^d
Electrical/magnetic stimulation therapies
rTMS (Khedr et al., 2019)	√		√		4
SES + logopaedic dysphagia therapy (Baijens et al., 2013)	√			√	0
NMES + logopaedic dysphagia therapy (Park et al., 2018)			√^d	↔
NMES + effortful swallow + conventional dysphagia therapy (Heijnen et al., 2012)	√			√	0
Respiratory loading therapies
Aerobic + resistance training (Mavrommati et al., 2017)		√
Upper and lower limb muscle strength training (Alves et al., 2019)		√^d	√^d		0
Treadmill training (Pelosin et al., 2009)		√	√
Pursed lip + diaphragmatic pulmonary exercise (Güngen et al., 2017)		√	√
Breath-stacking or incentive spirometry (Ribeiro et al., 2018)		√
Pulmonary rehabilitation + upper extremity exercises (Köseoğlu et al., 1997)		√
Aerobic + qigong^a (Burini et al., 2006)		√	↔		4
Inspiratory muscle training (Inzelberg et al., 2005)		√	↔
EMST (n = 8^b studies)	√	√^d	√	√^d	0
Respiratory muscle training (inspiratory muscle training or EMST; Huang et al., 2020; Reyes et al., 2018)		√	√
EMST + swallow postural techniques (Byeon, 2016)	√
EMST^c + air stacking (Reyes et al., 2020)		√
Voice loading therapies
Voice and choral singing treatment^e (Di Benedetto et al., 2009)	↔	√			20^#
Therapeutic singing^f (Stegemöller, Hibbing, et al., 2017; Stegemöller, Radig, et al., 2017)	√	√	√
ParkinSong^g (Tamplin et al, 2019; Tamplin et al., 2020)		√
Lee-Silverman voice treatment^h (Miles et al., 2017; El Sharkawi et al., 2002)	√	√	√	√

Note. rTMS = repetitive transcranial magnetic stimulation; SES = surface electrical stimulation; NMES = neuromuscular electrical stimulation; EMST = expiratory muscle strength training.

√ = significantly improved after intervention (p = .05); ↔ = no significant change after intervention; ^# = quality of voice worse after treatment.

^aQigong: breathing exercises with stretching and balancing.

^b(Claus et al., 2021; Cocks et al., 2022; Darling-White & Huber, 2017; Kuo et al., 2017; Pitts et al., 2009; Sapienza et al., 2011; Troche et al., 2010; Troche et al., 2014).

^cEMST program adapted for 6 d a week for 8 weeks.

^dDemonstrated the improvement in function with moderate to large effects (Cohen’s d).

^eVCST: oro-facial, neck shoulder exercises, and singing with cues.

^fTherapeutic singing: vocal exercises followed by group singing.

^gParkinSong: music-based vocal exercises, singing, social interaction, and conversational practice.

^hLee-Silverman Voice Treatment (LSVT): vocal exercises, reading, and conversation with loudness cue.

Table III. Participant characteristics.

Intervention	Sample size: IG/total	Age (years)^a		Gender (M/F)	Diagnosis (years)^a	Disease severity H&Y^a (range)	Dropout % IG/CG
Swallow-related therapies
Effortful swallow + tongue exercises (Wang et al., 2018)	26/26		62	19/7	9	2 (1–3)	0/NA
Tongue isometric pressure exercises +  traditional tongue training therapy (Plaza & Ruviaro Busanello-Stella, 2022)	30/60		69	34/26	7	2.8	0/0
Motor swallow exercises (Argolo et al., 2013)	17/17		59	10/5	7	2 (1–4)	12/NA
Video assisted swallow training (Manor et al., 2013)	21/42		69	24/18	8	2	0/0
Biofeedback in strength & skill training (Athukorala et al., 2014)	10/10		67	7/3	7	3 (2–3)	0/NA
Electrical/magnetic stimulation therapies
rTMS (Khedr et al., 2019)	22/33		59	NR	6	3^b	14/0
SES + logopaedic dysphagia therapy (Baijens et al., 2013)	67/109		69	66/24	5	2^b (1–5)	16/23
NMES + logopaedic dysphagia therapy (Park et al., 2018)	9/18		59	8/10	NR	NR	0/0
NMES + effortful swallow + conventional dysphagia therapy (Heijnen et al., 2012)	60/90		68^b	65/25	NR	2^b	3/0
Respiratory loading therapies
Aerobic + resistance training (Mavrommati et al., 2017)	37/37		65	21/16	NR	UPDRS III 16 (0–43)	31/NA
Upper and lower limb muscle strength training (Alves et al., 2019)	16/32		66	16/16	5	1 (1–2), UPDRS: 74	25/0
Treadmill training (Pelosin et al., 2009)	10/10		69	4/6	8	2 (1–2.5)	0/NA
Pursed lip + diaphragmatic pulmonary exercises (Güngen et al., 2017)	34/34		68	21/13	6	1.6	24/NA
Breath-stacking or incentive spirometry (Ribeiro et al., 2018)	14/14		66	9/5	NR	2 (1–3)	6/NA
Pulmonary rehabilitation + upper extremity exercises (Köseoğlu et al., 1997)	9/9		55	4/5	6	1 (1–2)	22/NA
Aerobic + qigong^a (Burini et al., 2006)	26/26		65	9/17	11	3 (2–3)	15/15
Inspiratory muscle training (Inzelberg et al., 2005)	10/20		62	18/2	8	3 (2–3)	50/40
EMST (Torche et al., 2010)	32/65		67	47/13	NR	3 (2–4)	6/9
EMST (Sapienza et al., 2011) continuation of study by Troche et al. (2010)	32/65		67	47/13	NR	3	6/9
EMST (Claus et al., 2021)	25/50		67	37/8	7	2.5 (2–4)	4/16
EMST (Cocks et al., 2022)	16/16		75	15/1	7	NR	24/NA
EMST (Kuo et al., 2017)	9/13		(51-70)	7/6	(3-10)	(1–3)	23
EMST (Pitts et al., 2009)	10/10		73	10/0	NR	3 (2.5–3)	0/NA
EMST (Troche et al., 2014)	10/10		70	8/2	NR	3 (2–3)	0/NA
EMST (Darling-White et al., 2017)	12/12		75	9/3	8	(1–3)	0/NA
RMT (inspiratory muscle training or EMST; Reyes et al., 2018)	21/31		70	17/14	NR	1 (1–3)	19/28
RMT (inspiratory muscle training or EMST; Huang et al., 2020)	38/75		64	42/33	6	2 (1–3)	0/0
EMST + swallow postural techniques (Byeon, 2016)	18/33		64	31/2	NR	H & Y ≤ 3: 26, H & Y > 4: 7	0/0
EMST + air stacking (Reyes et al., 2020)	22/33		69	18/15	NR	1 (1–3)	0/0
Voice loading therapies
Voice + choral singing treatment (Di Benedetto et al., 2009)	20/20		66	13/17	7	2^b IQR (1.5–2.5)	0/NA
Therapeutic singing (Stegemöller, Radig, et al., 2017)	18/24		68	8/16	7	UPDRS:55	0/0
Therapeutic singing (Stegemöller, Hibbing, et al., 2017)	18/27		67	10/17	NR	UPDRS:56	0/0
ParkinSong (Tamplin et al., 2019)	47/75		74	46/29	9	2 (2–3)	6/3
ParkinSong (Tamplin et al., 2020)	47/75		74	46/29	9	2 (2–3)	6/3
Lee-Silverman voice treatment (El Sharkawi et al., 2002)	8/8		70	6/2	NR	3 (1.5–2.5)	0/NA
Lee-Silverman voice treatment (Miles et al., 2017)	20/20		68	14/6	6	UPDRS : 25 (9–48)	0/NA

Note. IG = intervention group; CG = control group; M/F = male/female (in numbers); H&Y = Hoehn and Yahr Scale; UPDRS = Unified Parkinson's Disease Rating Scale;   NR = not reported; NA = not applicable; EMST = expiratory muscle strength training; NMES = neuromuscular electrical stimulation; RMT = respiratory muscle strength training; rTMS = repetitive transcranial magnetic stimulation; SES = surface electrical stimulation.

^amean.

^bmedian.

Table IV. Dosage and intensity of the interventions.

Intervention and description	Number of sessions	Session duration (minutes)	Intervention time period (weeks)
Swallow-related therapies
Effortful swallow + tongue exercises (Wang et al., 2018)	120 (2 × 5 × 12)	NR^a	12
Tongue isometric pressure exercises + traditional tongue training therapy (Plaza & Ruviaro Busanello-Stella, 2022)	√		√
Motor swallow exercise (vocal exercises + tongue hold + supraglottic swallow + swallow muscle range of movements; Argolo et al., 2013)	50 (2 × 5 × 5)	NR^a	5
Video assisted swallow training (Manor et al., 2013)	6	30	6
Biofeedback in strength and skill training (Athukorala et al., 2014)	10 (5 × 2)	60	2
Electromagnetic stimulation therapies
rTMS (Khedr et al., 2019)	25^b	NR^a	14
SES + logopaedic dysphagia therapy (Baijens et al., 2013)	15	30	3
NMES + logopaedic dysphagia therapy (Park et al., 2018)	13-15	30	3-5
NMES + effortful swallow + CDT (Heijnen et al., 2012)^c	20 (5 × 4)	60	4
Respiratory-loading therapies
Aerobic + resistance training (Mavrommati et al., 2017)	48 (2 × 24)	60	24
Upper and lower limb muscle strength training (Alves et al., 2019)	32 (2 × 16)	30-40	16
Treadmill training (Pelosin et al., 2009)	12 (3 × 4)	30	4
Pursed lip + diaphragmatic pulmonary exercises (Güngen et al., 2017)	NR	NR	12
Breath-stacking or incentive spirometry (Ribeiro et al., 2018)	2f	NR^a	3
Pulmonary rehabilitation + upper extremity exercises (Köseoğlu et al., 1997)	15 (3 × 5)	60	5
Aerobic + qigong (Burini et al., 2006)	40c	45-50	14
Inspiratory muscle training (Inzelberg et al., 2005)	72 (6 × 12)	30	12
EMST (Byeon et al., 2016; Claus et al., 2021; Kuo et al., 2017; Pitts et al., 2009; Sapienza et al., 2011; Troche et al., 2010; Troche et al., 2014)	20 (5 × 4)	10-20	4
EMST (Darling-White et al., 2017)	24d	30	8
Respiratory muscle training (inspiratory muscle training or EMST; Reyes et al., 2018)	48 (6 × 8)	NR^a	8
Respiratory muscle training (inspiratory muscle training or EMST; Huang et al., 2020)	20 (5 × 4)	50	4
EMST + swallow postural techniques (Byeon, 2016)	20 (5 × 4)	50	4
EMST + air stacking (Reyes et al., 2020)	48 (6 × 8)	NR^a	8
Voice loading therapies
Voice + choral singing treatment (Di Benedetto et al., 2009)	33e	180	10-13
Therapeutic singing (Stegemöller, Hibbing, et al., 2017; Stegemöller, Radig, et al., 2017)	16 (2 × 8)	60	8
ParkinSong (Tamplin et al., 2019)	12(1 × 12)	120	12
ParkinSong (Tamplin et al., 2020)	52(1 × 52)	120	52
Lee-Silverman voice treatment (El Sharkawi et al., 2002; Miles et al., 2017)	16 (4 × 4)	50-60	4

Note. NR = not reported; rTMS = repetitive transcranial magnetic stimulation; SES = surface electrical stimulation; NMES = neuromuscular electrical stimulation; CDT = conventional dysphagia therapy; EMST = expiratory muscle strength training.

^aQuantified the exercises and repetition but not mentioned the exact duration of a session.

^b2 weeks (5 days/week for 10 days) and five booster sessions every month for 3 months.

^cAerobic training for 7 weeks (45 min for each session), 8 weeks no treatment, and qigong for 7 weeks (50 min for each session; 22 weeks in total).

^d4 Pre-training sessions (1.5 hr, once a week for 4 weeks) and four training sessions (30 min, once a week for 4 weeks only; for two participants it took 5 weeks).

^e20 hr of collective speech therapy (two sessions of 1 hr every week over 10 weeks for 20 sessions in total), plus 26 hr of choral singing (13 sessions of 2 hr every week for 13 weeks).

^fCross-over trial each technique was conducted once with an interval of 7 days between each of the intervention.

Table V. Studies with cross-system effects.

Intervention (Author, year)	Study design	Immediate effects and maintenance effects	Risk of bias rating and level of evidence
Electrical/magnetic stimulation therapies
IG: rTMS CG: Sham rTMS (Khedr et al., 2019)	Randomised controlled trial	Swallow: VFSS (5 ml fluid, semisolid, solid): Solid swallows. ↓ Duration of hyoid movement*, ↓ pharyngeal transit time*, ↔ residue score. Fluid swallows. ↔ Duration of hyoid movement*, ↔ pharyngeal transit time*. ↔ PAS score. QOL: ↓ A-DHI^a, ↓ UPDRS III Follow-up: 3 months: quality of life measure improvements maintained at follow-up (no VFSS done at follow-up).	High I b
Respiratory loading therapies
IG: EMST CG: Sham EMST (Troche et al., 2010)	Randomised controlled trial	Swallow: VFSS (ten 5 ml trials of thin liquid and a trail of 3 oz sequential cup drinking): ↓ Duration of hyoid elevation, ↑ onset of bolus transit, ↑ UES opening*, ↑ UES maximum opening*, ↑ UES closure*, ↑ laryngeal closure, ↑ maximum laryngeal closure, ↑ laryngeal opening. QOL: ↑ SWAL-QOL. Functional swallow outcome: VFSS. ↔PAS score*, moderate effect (d = 0.55).	Low I b
IG: EMST CG: Sham EMST (Claus et al., 2021)	Randomised controlled trial	Swallow: FEES (3 × 8 ml puree-IDDSI 4; 3 × 5 ml liquid-IDDSI 0; 3 × 3 × 0.5 cm^3 white bread-IDDSI 7): ↓ Total score*, ↓ residue score*, ↔ premature spillage, ↔ PAS score (baseline measure indicating no evidence of penetration-aspiration). Magnetencephalography: ↔ cortical activation (localised activation in bilateral pericentral cortex). QOL: ↓SDQ*, ↔ SWAL-QOL. Follow-up at 3 months: Improved measures were maintained at follow-up.	Low I b
IG: EMST + swallow postural techniques CG: EMST only (Byeon, 2016)	Randomised controlled trial	Functional swallow: VFSS: ↓ Videofluoroscopy Studies Scale Score.^a^,^b	Low I b
IG: EMST (Pitts et al., 2009)	Non-controlled trial (Before and after trial)	Cough/ respiratory: Pressure manometer: ↑ Maximum expiratory pressure*. Pneumotachograph & spirometer: Voluntary cough measures. ↔ Inspiratory phase duration, ↓ compression phase duration*, ↓ expiratory phase rise time*, ↑ cough volume acceleration*, ↔ inspiratory phase peak flow, ↔ expiratory phase peak flow, ↔ inspiratory phase duration, expiratory phase rise time. Functional swallow: VFSS (30 ml thin sequential swallow task): ↓ PAS score*.	Moderate III
IG: EMST (50% peak pressure threshold for each week; Cocks et al., 2022)	Non-controlled trial (Before and after trial)	Swallow: ↑ MASA scores*. Other: ↓ Sialorrhea* (SCS-PD), ↑ lip strength* (IOPI). Cough/respiratory: Spirometer. ↑ Voluntary peak cough flow*. QOL: ↑ SWAL-QOL*.	Serious III
Voice loading therapies
IG 1: Therapeutic singing high dosage IG2: Therapeutic singing low dosage (once a week session for 8 weeks; Stegemöller et al., 2017)	Non-randomised controlled trial (Cohort study)	Electromyography (3 × 10 ml thin condition and 3 × 10 ml pudding thick condition): LM = laryngeal muscles; SM = submental muscles; AUC = area under curve; EMG = electromyography. Thin liquid: Amplitude: ↔ LM peak amplitude, ↔ LM AUC, ↔ SM peak amplitude, ↔ SM AUC. Timing: ↔ LM rise time*, ↔ LM fall time*, ↔ LM EMG duration*, ↔ SM rise time, ↔ SM fall time*, ↔ SM EMG duration*. Thick liquid: Amplitude: ↔ LM AUC, ↑ SM peak amplitude*, ↔ SM AUC*, ↔ LM peak amplitude, ↔ LM AUC. Timing: ↑ SM fall time*, ↔ SM EMG duration*, ↔ SM rise time, ↔ LM rise time*, ↔ LM fall time*, ↔ LM EMG duration*. Group and condition interaction effects: Thick-SM AUC*, Thin-SM fall time*, ↔ all other measures. QOL: ↔ SWAL-QOL, ↓ UPDRS total score*.	Serious II a
IG 1: Therapeutic singing high dosage IG2: Therapeutic singing low dosage (once a week session for 8 weeks; Stegemöller et al., 2017)	Non-randomised controlled trial (before and after trial)	Cough/respiratory: Pressure metre: ↔ maximum expiratory pressure^b, ↔ maximum inspiratory pressure^b Other measures: Voice and speech (decibel metre, chromatic tuner on iPad): ↔ phonation duration^b, ↔ phonation range, ↔ vocal intensity. QOL: ↔ voice related quality of life*.	Serious II a
IG1: ParkinSong (weekly for 12 weeks) IG2: ParkinSong (monthly for 3 months) CG1: Support group (weekly for 12 weeks) CG2: Support group (monthly for 3 months; Tamplin et al., 2019)	Non-randomised controlled trial (4-arms study)	Cough/respiratory: Group comparison: IG1 vs other groups Pressure metre: ↑ maximum expiratory pressure^a, ↔ maximum inspiratory pressure, ↔ sniff nasal inspiratory pressureOther measures: Group comparison: IG1 vs other groups Voice and speech: (PRAAT software for speech analysis and sound level metre): ↑ vocal intensity monologue^a, ↑ vocal intensity loud sentence task^a, ↑ intelligibility (speech intelligibility test), ↑ intelligibility (perceptual), ↔ maximum phonation length. ↓ Voice-related QOL*.	Serious II a
IG1: ParkinSong (weekly for 52 weeks) IG2: ParkinSong (monthly for 12 months) CG1: Support group (weekly for 52 weeks) CG2: Support group (monthly for 12 months; Tamplin et al., 2020)	Non-randomised controlled trial (continuation of Tamplin et al., 2019)	Cough/ respiratory: Group comparison: IG1 vs other groups Pressure metre: ↔ maximum expiratory pressure, ↔ maximum inspiratory pressure, ↔ sniff nasal inspiratory pressure. Other measures: Group comparison: IG1 vs other groups Voice and speech: (PRAAT software for speech analysis and sound level metre): ↑ vocal intensity (monologue^a),↑ intelligibility (perceptual), ↔ vocal intensity loud sentence task, ↔ intelligibility (SIT), ↔ maximum phonation time. ↓ Voice-related QOL^a	Serious II a
IG: VCST (Di Benedetto et al., 2009)	Non-controlled trial (pilot test-retest non-controlled study)	Swallow: Videostroboscopy: Vocal folds (VF) ↔ VF movement symmetry, ↔ VF movement amplitude, ↔ glottic closure configuration, ↔ VF rest tremor, ↔ VF tremor during phonation. Cough/respiratory: Spirometry: ↓ functional residual capacity*, ↔ forced vital capacity percentage, ↔ forced expiratory volume in one second percentage. Pressure metre: ↑ maximum expiratory*, ↑ maximum inspiratory pressure*. Other measures: Speech and voice (CSL- MDVP): ↑ maximum phonation time*, ↔ frequency measures, ↔ perturbation measures, ↔ frequency and amplitude tremor index. Quality of voice analysis: ↑ prosodia reading visual analogue scale*, ↔ prosodia monologue visual analogue scale, ↓ fatigue during reading*, ↔ fatigue during monologue.	Serious III
IG: LSVT (Miles et al., 2017)	Non-controlled trial (Prospective non-randomised single-blinded cohort intervention study)	Swallow: VFSS (20 ml thin liquid, 100 ml thin liquid sequential swallow, 5 ml paste): Timing measures: ↑ PES opening duration*, ↔ bolus transit time, ↔ airway closure time during swallow, ↔ duration of hyoid maximally displaced during swallow. Displacement measures: ↑ PES maximum opening*, ↔ maximum hyoid displacement, ↔ maximum hyolaryngeal displacement, ↔ pharyngeal constriction ratio. Anatomical measure: ↓ pharyngeal area at rest*. ↓ paste residue*. Straw drinking (100 ml): ↔ duration, ↔ number of swallows, ↔ number of breaths. Cough/respiratory: Spirometry reflexive cough: ↔ compression phase duration, ↑ peak expiratory flow rate*, ↑ peak expiratory flow rise time*, ↔ cough volume acceleration. Other measures: Voice and speech (sound level metre): ↑ maximum phonation time*, ↑ sound pressure level reading*, ↑ sound pressure level conversation*. QOL/disease severity: ↓ Parkinson’s Disease Questionnaire-8*, ↓ Eating Assessment Tool-10*. Follow-up (6 months): improvements were maintained at follow-up.	Low III
IG: LSVT (El Sharkawi et al., 2002)	Non-controlled trial (before and after trial)	Swallow: VFSS (Two trials of 1 ml, 3 ml, 5 ml, and 10 ml cup drinking, 2 ml pudding paste, ¼ cookie): Swallow motility pre-post treatment comparison: Improved: tongue lateralisation, tongue coordination, antero-posterior tongue movement (100% cup drinking), antero-lateral tongue stabilisation, tongue strength, pharyngeal swallow trigger (25% liquids, 66% cookie). Reduced: rock-like tongue motion, oral residue (50% liquids, 12.5% paste, 25% cookie), tongue base and valleculae residue (50% in total for all bolus sizes and consistency). Not improved: tongue lateralisation on cookie bolus, delayed laryngeal vestibule closure. Penetration and aspiration: not evident before or after intervention. Temporal measure: ↓ oral transit time for paste*, ↓ oral residue percentage for 3 ml and 5 ml*, ↑ oropharyngeal efficiency scorefor cup drinking*. (↔ for other volume and consistencies trialled) Other measures: Voice and speech (sound level metre and CSpeech): ↑ sound pressure level for vowel phonation, reading, happy day conversation*, ↔ fundamental frequency (reading and happy day), ↔ clarity of speech, ↔ voice handicap index.	Moderate III

Note. IG = intervention group; CG = control group. ↑ = significantly increased; ↔ = no significant change; ↓ = significantly decreased (improved); level of significance = p < .05; * = significant within-group change from pre- to post-intervention in the intervention group. A-DHI = Arabic Dysphagia Handicap Index; EMST = expiratory muscle strength training; FEES = fiberoptic endoscopic evaluation of swallowing; IDDSI = International Dysphagia Diet Standardisation Initiative; IOP I = Iowa Oral Performance Instrument; LSVT = Lee Silverman Voice Treatment; MASA = Mann Assessment of Swallowing Ability; PAS = Penetration-Aspiration Scale; P ES = pharyngoesophageal sphincter; QOL = quality of life; rT MS = repetitive transcranial magnetic stimulation; SCS-P D = Sialorrhea Clinical Scale for Parkinson’s Disease SDQ = Swallowing Disturbances Questionnaire SWAL-QOL = Swallowing Quality of Life questionnaire; UES = upper esophageal sphincter; UP DRS = Unified Parkinson’s Disease Rating Scale; VCST = Voice and choral singing treatment; VFSS = videofluoroscopy swallow study.

^aChange in intervention group significantly larger than change in control group.

^bSignificant within-group change from pre- to post-intervention in both intervention and control group.

Figure 2. Risk of bias for randomised (RoB2) and non-randomised (ROBINS-I) trials.

Table VI. Best evidence statement of behavioural therapies in improving swallow and respiratory/cough measures in individuals with Parkinson’s disease.

Outcome measures	Intervention	Best evidence statement (summary findings of the significant changes of the outcome measures from the studies rated low risk of bias)
Swallow	VAST (Manor et al., 2013)	Level 1b evidence: reduction in pharyngeal residue (FEES).
	Surface electrical stimulation and logopaedic dysphagia therapy (Baijens et al., 2013)	Level 1b evidence: reduction in piecemeal deglutition (VFSS), reduction in delayed initiation pharyngeal reflex (FEES; entire population pre- and post-comparison, no group difference).
	EMST (Troche et al., 2010)	Level 1b evidence: VFSS durational measures. Reduction in hyoid elevation, increase in onset of bolus transit, increase in UES opening, increase in UES maximum opening, increase in UES closure, increase in laryngeal closure, increase in maximum laryngeal closure, increase in laryngeal opening. Penetration-Aspiration Scale scores: moderate effect on swallow functional outcome (d = 0.55).
	EMST (Claus et al., 2021)	Level 1b evidence: reduction in total score, reduction in residue score (FEES).
	EMST and swallow postural techniques (Byeon, 2016)	Level 1b evidence: reduction in Videofluoroscopy Studies Scale score.
	Motor swallowing exercise (Argolo et al., 2013)	Level III evidence: significant association between treatment failure vs lingual pumping and treatment failure vs dental absence. VFSS examination: reduction in loss of bolus control, reduction in piecemeal swallow, reduction in tongue residue, reduction in pyriform residue, reduction in vallecular residue.
	LSVT (Miles et al., 2017)	Level III evidence: increase in PES opening duration, increase in PES maximum opening, reduction in pharyngeal area at rest, reduction in paste residue (VFSS).
Respiratory/ cough	EMST (Sapienza et al., 2011)	Level 1b evidence: increase in maximum expiratory pressure (pressure manometer).
	Full-body strength training (Alves et al., 2019)	Level 1b evidence: increase in maximum inspiratory pressure with moderate effect size (manovacuometer).
	Aerobic training (Burini et al., 2006)	Level 1b evidence: reduction in peak oxygen uptake, reduction in double product peak, reduction in oxygen uptake rate (spirometer), reduction in perception of breathlessness (Borg scale). Increase is six minute walking test (exercise tolerance).
	Breath-stacking and incentive spirometer (Ribeiro et al., 2018)	Level 1b evidence: increase in total tidal volume (plethysmography).
	LSVT (Miles et al., 2017)	Level III evidence: spirometry reflexive cough study. Increase in peak expiratory flow rate, increase in peak expiratory flow rise time.
QOL/disease severity	VAST (Manor et al., 2013)	Level 1b evidence: decrease in Swallowing Disturbance Questionnaire score, increase in SWAL-QOL score.
	EMST (Troche et al., 2010)	Level 1b evidence: increase in SWAL-QOL score.
	EMST (Claus et al., 2021)	Level 1b evidence: decrease in Swallowing Disturbance Questionnaire score.
	Motor swallowing exercises (Argolo et al., 2013)	Level III evidence: SWAL-QOL. Increase in symptom frequency, increase in fear domains. Swallow complaints. Decrease in difficulty in moving food when chewing.
	LSVT (Miles et al., 2017)	Level III evidence: decrease in Parkinson’s Disease Questionnaire-8, decrease in Eating Assessment Tool-10 score.

See Supplementary Appendix 3 for full definitions of levels of evidence (Level 1a = meta-analysis of RCTs and Level IV = expert option/clinical experience only).

Note. Reported measures: level of significance p ≦ .05. EMST = expiratory muscle strength training; FEES = fiberoptic endoscopic evaluation of swallowing; LSVT = Lee Silverman voice treatment; PES = pharyngoesophageal sphincter; QOL = quality of life; SWAL-QOL = Swallowing Quality of Life questionnaire; UES = upper oesophageal sphincter; VAST = video assisted swallow training; VFSS = videofluoroscopy.

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