Hidden Undernourishment: Sex and Disease Factors Associated with the Underrating of Swallowing Function.

Accurate assessment of swallowing function is essential to prevent aspiration pneumonia and nutritional decline. However, in hospitalized patients, discrepancies are often observed between clinical assessments and the actual oral intake. We retrospectively analyzed 5,091 patients who underwent a videofluoroscopic swallowing study or videoendoscopic evaluation of swallowing (VE) at our hospital between 2018 and 2024. The Discrepancy Index (DI), as the difference between the Food Intake LEVEL Scale and Fujishima's swallowing ability grade, was calculated. Patients with DI ≤ - 2 were classified as the "underestimated group". Logistic regression analysis was conducted to identify the associated factors. The underestimated group accounted for 22.5% of the cases. Female sex (OR = 1.45, p < 0.001), VE use (OR = 1.68, p < 0.001), pulmonary disease (OR = 1.63, p = 0.001), and disuse-related physical decline (hereafter referred to as disuse syndrome) (OR = 1.71, p = 0.001) were significantly associated with underestimation. The subgroup analyses revealed that these associations were more prominent in men with pulmonary and disuse-related conditions. Overestimation though rare (< 3%) was clinically important. Over 20% of patients were likely to receive unnecessarily restrictive diets due to underestimation of their swallowing function. Such underestimation may be influenced by inaccurate assessments or clinicians' safety concerns, as reported in previous studies. Although sex showed a statistical effect on the DI, it did not indicate a consistent pattern of under- or over-estimation between sexes. Timely and accurate assessment of swallowing through an interdisciplinary collaboration is essential to avoid unnecessary fasting, prevent nutritional decline, and reduce the risk of developing sarcopenic dysphagia.