Table 7.

Summary of study results, listed by technology, with levels of evidence rated according to the scheme of the National Health and Medical Research Council of Australia [66]

Author	Sample Size	Technology	Finding	Level of evidence
Lee, Sejdic, Steele, & Chau [32]	17	Accelerometry	Accelerometry signals exhibited a more prominent, well-defined pattern as bolus viscosity increased. Nectar-thick and honey-thick apple juices were associated with longer swallow durations on average than water and thin barium.	IV
Steele & Van Lieshout [28]	8	Articulography	Greater variation in tongue movement for honey-thick items and least for thin items.	IV
Steele & Van Lieshout [29]	8	Articulography	Longer tongue movement durations and higher variability seen with honey-thick liquids compared to the nectar and thin.	IV
Taniwaki, Gao, Nishinari, & Kohyama [27]	6	Auscultation/Acoustics	Sounds associated with swallowing water were of longer duration and of higher intensity for water than for yogurt and konjac jelly.	IV
Anderson, Throckmorton, Buschang & Hayasaki [39]	26	Camera recordings of chewing behavior	Greater muscular effort when chewing harder gum produces a greater excursive range and velocities of mandibular movement except during the occlusal phases of chewing when the harder gum slows the mandible.	IV
Gisel [18]	143	Camera recordings of chewing behavior	Texture determined very strongly how long a bite of food was chewed, with solids taking longest, followed by gelatin and puree, respectively. As children became older they became more efficient at chewing a comparable bite of food, i.e. chewing time decreased for each texture.	III-2
Barata, de Carvalho, Carrara-de Angelis, de Faria, & Kowalski [48]	23	Naso-endoscopy	Thicker consistencies and solid foods were more likely to lead to residue. Thicker consistencies and solid foods were less likely to elicit laryngeal penetration/aspiration and nasal regurgitation.	IV
Butler, Postma, & Fischer [33]	22	sEMG	Viscosity (honey-thick vs. thin] did not alter swallow apnea duration in healthy adults.	IV
Igarashi, Kawasaki, Nomura, Sakai, Ueno, Ashida, & Miyaoka [30]	12	sEMG	Overall trend for longer durations of sEMG and laryngeal movement with increasing thickness.	IV
Inagaki, Miyaoka, Ashida, & Yamada [36]	9	sEMG	Tougher and more adhesive foods prolonged the duration of anterior tongue, but not suprahyoid muscle activity during swallowing in normal subjects.	IV
Inagaki, Miyaoka, Ashida, & Yamada [37]	9	sEMG	Foods of thicker consistency elicited a trend towards higher integrated suprahyoid sEMG amplitude and longer sEMG durations.	IV
Inagaki, Miyaoka, Ashida, & Yamada [38]	9	sEMG	The swallowing of harder and more adhesive foods was associated with stronger integrated and cumulated anterior tongue and suprahyoid EMGs. EMG activity increased in a stepwise fashion as the concentration of the thickening agent rose from low to high.	IV
Karkazis [46]	6	sEMG	Findings agree with those reported in dentate subjects and complete denture wearers: harder foods require higher chewing rates, higher EMG activity and higher relative contraction times, accompanied by shorter cycle durations.	IV
Karkazis & Kossioni [41]	22	sEMG	The mean values for integrated EMG, duration of chewing cycle, the chewing rate and the relative contraction time during swallowing were significantly higher for the carrots compared to the gum. A strong inverse correlation was found between chewing rate and cycle duration. Adjustments to food consistency are made by altering chewing rate, the duration of the chewing cycle and integrated EMG activity.	IV
Karkazis & Kossioni [47]	9	sEMG	In experienced denture wearers, harder foods (i.e. carrots) showed higher rates of chewing, higher masseter EMG measures of muscle force and shorter cycles than softer foods (apple).	IV
Reimers-Neils, Logemann, & Larson [26]	5	sEMG	Thick paste stimuli elicited significantly longer “swallow duration” (from sEMG) compared to liquids and thin pastes. Multi-peaked sEMG patterns (rather than single peaked patterns) were more common with the thick pastes. Peak amplitudes for both submental and infrahyoid EMG were higher for the thick paste consistency compared to both liquids and thin pastes.	IV
Ruark, McCullough, Peters, & Moore [19]	30	sEMG	Submental and strap muscle activity were longer for cheese spread compared to water. Strap muscle activity was longer for pudding and cheese spread vs. water. Amplitude was also higher for cheese spread than the other stimuli.	III-2
Nagatomi, Yoshimine, Miura, Tanaka & Arai [40]	12	Texture profile analysis after oral processing	Changes in the mechanical properties of the bolus due to oral processing are dependent on the texture of the food. All foods appear maintain a constant level of cohesiveness across oral processing (0.5). Immediately before swallowing, all three test foods had similar factor structures based on 5 mechanical properties studied using principal component analysis.	IV
Hoebler, Karinthi, Devaux, Guillon, Gallant, Bouchet, Melegari & Barry [42]	12	Texture profile analysis after oral processing.	The dry matter content of the food bolus influences the chewing time but is not the only variable to take into account. The size reduction of food, its de-structuring and the rate of starch hydrolysis depends on the chewing time as well as the physical characteristics of ingested food.	IV
Youmans, Youmans, & Stierwalt [35]	96	Tongue Pressure Measurement	Comparisons within volume show clear trends for increasing maximum swallowing pressure and percent maximum swallowing pressure from thin to nectar to honey to puree.	III-2
Chi-Fishman & Sonies [53]	31	Ultrasound	Spoon-thick liquids elicited longer durations of hyoid shadow movement than thin and nectar.	IV
Bingjie, Tong, Xinting, Jianmin, & Guijun [24]	205	VFSS	Penetration and aspiration frequency reduce as consistency becomes thicker. Oral transit times are longer for bread than for liquid consistencies (thin and paste). Pharyngeal transit time increases from thin to paste to bread in healthy adults. Pharyngeal delay is shorter for paste and bread than for thin in healthy adults. In stroke patients who aspirate, pharyngeal delay and pharyngeal transit are longer for paste and for bread than with thin liquids. In healthy adults, there are trends towards larger hyoid and laryngeal excursion from thin to paste to bread.	III-2
Bisch, Logemann, Rademaker, Kahrilas, Lazarus [22]	28	VFSS	Pudding elicited significantly longer UES opening durations and significantly shorter duration of tongue base contact. Pharyngeal delay time was significantly shorter with pudding in the stroke patients.	III-2
Chen, Peele, Donati, Ott, Donofrio, & Gelfand [51]	41	VFSS	Frequency of aspiration in patients studied decreased as viscosity increased.	IV
dos Santos, Cassiani, & Dantas [20]	32	VFSS	No dramatic trends related to texture in either group.	III-2
Goldfield, Smith, Buonomo, Perez, & Larson [17]	10	VFSS	Nectar thick barium flows more slowly through the pharynx than barium intended to simulate breast milk in NICU babies.	IV
Ishida, Palmer, & Hiiemae [31]	12	VFSS	There were no differences in forward or upward displacement of the hyoid across the 4 solids tested.	IV
Lee, Kim, Kim, & Lee [52]	29	VFSS	Mixed consistency was less likely to be aspirated than thin and more likely to be aspirated than rice. Residue was more likely for rice and mixed than for thin. Pharyngeal delay time was longer for mix compared to rice. Penetration-aspiration was significantly worse for mix than for rice, but better than for liquid. Location of bolus at swallow onset for mixed matched that seen for liquid.	IV
Lin, Hsiao, Chang, Ting, Chen, Chen, & Wang [49]	20	VFSS	Oral transit times were longer for paste consistency than for thin barium. Pre-treatment (functional electrical stimulation), hyoid displacement durations were shorter and vallecular residue was greater for paste consistency than for thin barium.	IV
Linden, Tippett, Johnston, Siebens, & French [25]	3	VFSS	On average, the bolus head was further advanced into the pharynx (past the faucial pillars) with the paste versus the thin liquid barium, in these 3 patients. Not clear whether they used command swallow paradigm.	IV
Oommen, Kim, & McCullough [23]	72	VFSS	Thin vs. nectar-thick barium did not alter stage transition duration or laryngeal closure duration in stroke patients.	III-2
Saitoh, Shibata, Matsuo, Baba, Fujii & Palmer [45]	15	VFSS	Chewing and initial consistency altered the relationship between food transport and swallow initiation. When liquids are chewed, or when consuming mixed consistencies, a portion of the bolus reaches the hypopharynx before swallow onset. Chewing reduces the effectiveness of the posterior tongue-palate seal, allowing oral contents to spill into the pharynx.	IV
Troche, Sapienza, & Rosenbek [50]	10	VFSS	Pudding thick consistency was associated with significantly longer oral transit times, a greater number of tongue pumps per bolus and lower (better) PAS scores than thin barium. There were no significant differences in pharyngeal transit time.	IV
Funami, Ishihara, Nakauma, Kohyama and Nishinari [43]	9; 7	Multiple methods: mechanical bolus compression; sensory profiling; sEMG; acoustics	Duration of oral processing (based on suprahyoid EMG activity) for both gels was longer than for data on water, and increased with increased gel hardness. Acoustic data suggested more rapid bolus flow for the mixed gels than for the simple gels. Mixed gels were rated to have higher cohesiveness and greater ease of swallowing than simple gels. Differences in textural attributes of these gels exist even when hardness is uniform.	IV
Kim & Han [21]	20	Multiple methods: salivary measures and viscosity measures after oral processing	Foods differ in viscosity pre and post oral phase, based on holding in the mouth (no chewing other than thick rice gruel). Demonstrates that viscosity becomes lower as a function of the oral phase. Stroke patients chewed more, had longer oral phases.	III-2
Ashida, Iwamori, Kawakami, Miyaoka & Murayama [44]	18	Multiple methods: sEMG and texture profile analysis after oral processing	Chewing time and number of chewing cycles were correlated with hardness of the stimuli (longer chewing for increased hardness). Hardness and other rheological properties of agars do not affect normalized measures of cumulative masseter muscle EMG amplitude and duration, based on analysis of the first and last chewing cycles in chewing sequences.	IV

Abbreviations: sEMG = surface electromyography; VFSS = videofluoroscopic swallowing study

Levels of evidence: III-2: evidence from comparative studies with concurrent controls without randomized allocation (cohort studies), case-control studies, or interrupted time-series with a control group; III-3: evidence from comparative studies with historical control, two or more single-arm studies, or interrupted time-series without a parallel control group; IV: evidence from case series, either post-test or pre-test and post-test, or superseded reference standards; V: expert opinion, physiology, bench research or “first principles” studies.