Blood Thiamine Level and Cognitive Function in Older Hospitalized Patients

Aim: We sought to identify any association between whole blood thiamine level and functional status in older hospitalized patients. Methods: This cross-sectional study retrospectively analyzed the results of routine measurements of whole blood thiamine levels of 233 older patients who were consecutively hospitalized to a geriatric acute care ward. Nutritional status, depression, and the participants' cognitive impairment were evaluated using the Mini Nutritional Assessment-Short Form, Depression in Old Age Scale, and Montreal Cognitive Assessment, respectively. Activities of daily living were determined using Barthel Index (BI) on admission and at the time of discharge. Diagnoses of dementia and delirium were derived from the patients' medical records. Results: Of 233 participants (mean age 82.1 [7.1]), 47.0% and 39.0% were at risk of malnutrition and malnourished, respectively. There was no thiamine deficiency (<20 ng/mL) in total population. Nearly all patients (95%) were screened with impaired cognitive function, in which 36% and 9% had the diagnosis of dementia and delirium, respectively. Patients with dementia (P = .040) and delirium (P = .002) demonstrated lower mean thiamine blood levels compared to patients without. Mean blood vitamin B-1 was higher in patients with functional recovery (change in BI >= 5 points during hospitalization; P = .018). In a binary logistic regression analysis, blood vitamin B-1, weight loss, and female gender were the major independent risk factors for delirium but not for dementia. Conclusion: Despite the absence of thiamine deficiency, whole blood thiamine was lower in patients with dementia and delirium compared to those without. Higher thiamine levels were significantly associated with functional recovery during hospitalization.