Trial reportEnvironmental health and preventive medicine2026
Inhaled hinoki cypress essential oil improves saliva secretion and swallowing function in older adults with dysphagia: a randomized crossover study.
Trial report in Environmental health and preventive medicine, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.
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1 citing paper in PubMed.
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Authors and funding
6 authors.
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No grant is acknowledged in the PubMed record.
Abstract
backgroundOlfactory stimulation with hinoki cypress essential oil reportedly reduces stress hormones and enhances parasympathetic activity, which may in turn increase salivary secretion and facilitate swallowing. However, its effects on swallowing in older adults with dysphagia remain unclear.
methodsIn this placebo-controlled, single-blind, randomized crossover study, older adults with dysphagia (Food Intake Level Scale ≤9) underwent 5-minute olfactory stimulation with hinoki cypress essential oil or rice oil (placebo) in two sessions one week apart. Repetitive saliva swallowing test (RSST), 3 mL modified water swallowing test (MWST), 30 mL water swallowing test (WST), saliva secretion for 5 minutes, blood pressure, and heart rate were measured before and after each stimulation. Changes from pre- to post-stimulation were compared within each condition and between conditions using Wilcoxon's signed-rank test.
resultsThirty-four participants (47% women; 80 ± 10 years) were included. Hinoki cypress essential oil significantly improved RSST (median difference 0.5, 95% CI 0.0-1.0; p = 0.004), MWST (0.5, 95% CI 0.0-1.0; p = 0.003), and saliva secretion (1.0 mL, 95% CI 0.5-2.0; p = 0.002), whereas placebo produced no significant change (all p > 0.05). Improvements in swallowing function were greater with hinoki than with placebo. The increase in saliva secretion following hinoki stimulation was not associated with changes in RSST or MWST scores.
conclusionsBrief olfactory stimulation with hinoki cypress essential oil improved swallowing function and increased saliva secretion in older adults with dysphagia compared with placebo in a randomized crossover design. Hinoki cypress essential oil inhalation may represent a simple, noninvasive adjunctive strategy for dysphagia management, warranting confirmation in larger and longer trials.
trial registrationThis study was registered in the UMIN Clinical Trials Registry (UMIN-CTR) under registration number UMIN000053271.
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