Abstract
BACKGROUND: Semi-solid foods are widely consumed by older adults, yet the influence of their physical properties on swallowing remains unclear. OBJECTIVES: To examine how variations in shape retention and spreadability affect swallowing in adults aged ≥75 years. DESIGN: An open-label randomized crossover trial with two food tests. SETTING: Controlled experimental setting. PARTICIPANTS AND NUMBERS ANALYZED: Test 1 enrolled 21 adults and Test 2 enrolled 28; after exclusions, 14 and 16 were analyzed (mean ages 81.6 and 78.6 years). INTERVENTIONS: Participants ingested three semi-solid foods (P, Q, S) differing in physical properties. OUTCOMES: Primary outcomes were oral processing time (OPT) and swallowing duration (SD), measured by a neck-worn electronic stethoscope and synchronized video. Secondary outcomes were subjective ratings of swallowing ease and food properties. Medians of five bites were analyzed, and first-fifth bite differences assessed. RESULTS: Subjective ratings differed only in collectability in Test 2. In Test 1, OPT was longer for P than Q (median difference 1.04 s, 95 % CI 0.15-2.04; p = 0.030). In Test 2, OPT was longer for S than P (median difference -1.88 s, -2.81 to -0.74; p = 0.001). SD did not differ significantly. With repeated swallows, OPT variance increased and SD variance decreased for P and Q, while both increased for S. HARMS: None observed. CONCLUSIONS: Semi-solid food properties affect swallowing in older adults. Shape retention contributes to distinct swallowing patterns, supporting individualized food selection to promote safe intake. TRIAL REGISTRATION: UMIN000053442, UMIN000056840.