Subjects
A total of 85 subjects with AD were consecutively enrolled in the cross-sectional study between September 2021 and November 2022 from the Center for Cognitive Neurology, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University. All subjects were diagnosed with MCI due to AD (AD-MCI)[11] or dementia due to AD (AD-D)[12] according to the National Institute of Aging and Alzheimer’s Association (NIA-AA) criteria, and divided into the AD-MCI group and the AD-D group, respectively. AD patients meeting the following criteria were excluded from this study: (1) patients with other neurological diseases that affected cognition, including Parkinson’s disease, dementia with Lewy bodies, frontotemporal dementia, corticobasal degeneration, acute cerebrovascular disease involving the cerebral cortex, acute stroke that was temporally associated with cognitive impairment, etc; (2) patients with diseases affecting gait, including lower extremity fracture, femoral head necrosis, lower extremity arteriosclerosis obliterans, etc; (3) patients with other conditions leading to malnutrition, including hematological tumors, liver cirrhosis, severe systemic disease, or subtotal gastrectomy, etc; (4) patients were unable to cooperate with all the examinations for various reasons.
Demographic data
The general demographic data, including sex, age, age of onset, education level, marital status, apolipoprotein E (APOE) genotype, and several comorbidities including hypertension, hyperlipidemia, diabetes mellitus, hyperhomocysteinemia, myocardial infarction, atrial fibrillation, cerebral infarction, cerebral hemorrhage, thyroid disease, smoking and drinking, were collected.
The following 5 aspects of nutritional-related demographic data were collected according to the Global Leadership Initiative on Malnutrition (GLIM) criterion[13]:
Non-volitional weight loss
Non-volitional weight loss was defined as a self-reported body weight loss within the past 6 months, which categorized as < 5%, 5%-10% or > 10%[14].
BMI
BMI was calculated by dividing the measured body weight by the squared height (kg/m2), and was classified as underweight (BMI < 18.5 kg/m2), normal weight (BMI 18.5–23.9 kg/m2), overweight (BMI 24.0–27.9 kg/m2) or obese (BMI ≥ 28.0 kg/m2) according to Chinese adults classification standard[15, 16].
Muscle mass
circumferences of arm, waist, hip, and calf were measured to reflect the muscle mass of patients. The waist circumference was measured at the narrowest point of the trunk between the ribs and the upper part of the hip bone. The hip circumference was measured at the widest point of the hip and buttocks. The arm circumference was measured at the midpoint between the acromion and olecranon processes. The calf circumference was measured at the location where the calf was thickest[17].
Reduced food intake: Reduced food intake referred to a decrease in food intake over the past 3 months due to various reasons, including poor oral health, side effects of medication, depression, dysphagia, gastrointestinal complaints, anorexia, and insufficient nutrition support. It was classified into 4 categories: no reduction in intake, a 25%-50% reduction, a 50%-75% reduction, or a reduction of ≥ 75%[18].
Burden/inflammation
Burden/inflammation was defined as patients with major infections, burns, trauma, closed head injury, fever, negative nitrogen balance, congestive heart failure, chronic obstructive pulmonary disease, rheumatoid arthritis, chronic kidney or liver disease or cancer[13, 18].
Assessments of clinical symptoms
Global cognition of patients was assessed by the scales of Mini-Mental State Examination (MMSE)[19] and the Montreal Cognitive Assessment (MoCA)[20]. Neuropsychiatric symptoms were assessed by the Neuropsychiatric Inventory (NPI) scale[21]. ADL were assessed by the ADL scale, which includes basic ADL (BADL) and instrumental ADL (IADL)[22].
The nutritional status of patients was assessed by the Mini-Nutritional Assessment (MNA) scale[23]. The scoring categorizes subjects in the following manner: well-nourished (≥ 24 points), at risk of malnutrition (17-23.5 points) and malnourished (< 17 points). To avoid interference of cognitive performance and depression with nutritional assessment, we also analyzed a modified MNA (MNAm) scale, leaving out the question of “neuropsychological problem”[24].
The detailed description of these scales was provided in the Supplementary material 1.
Nutrition-related laboratory indicators
The venous blood samples of AD patients were collected from the median elbow under fasting condition the next morning after admission, and then sent to the clinical laboratory of Beijing Tiantan Hospital.
We collected a variety of nutritional-related laboratory variables to assess the nutritional status of patients, including hemoglobin A1c, fasting blood glucose, hemoglobin, blood urea nitrogen, creatinine, albumin, prealbumin, homocysteine, folic acid, and vitamin B12, etc in serum.
Gait parameters collection
The Codamotion 3D motion capture system (Charnwood Dynamics, Ltd., United Kingdom) was used to collect the bilateral gait parameters of patients by active infrared capture.
To record steady-state walking patterns, subjects were instructed to start walking approximately 1m before entering the infrared capture range. A successful trial is defined as the acquisition of more than three consecutive complete cycles of stereo motion data, and each task requires the acquisition of at least 6 successful trials.
The gait parameters, including speed (m/s), step length (m), step length time (s), stride length (m), stride time (s), cadence (steps/min), cadence (strides/min), and percentage of support (%), were collected. Cadence (steps/min) was defined as the number of steps per minute, and cadence (strides/min) was defined as the number of strides per minute. The variability of each gait parameter was represented by the coefficient of variation (CV): standard deviation/mean x 100[25].
Statistical analysis
Statistical analyses were performed by SPSS Statistics 25.0 (IBM Corporation, New York, USA). Statistical significance was defined as a two-sided P < 0.05.
Data were tested for normal distribution using the Kolmogorov-Smirnov test. Clinical characteristics, nutritional status and gait performance were compared between the AD-MCI and the AD-D groups. Continuous variables conforming to normal distribution were presented as means ± standard deviations (SD) and compared by two-tailed t test, non-normal distributed measurement variables were presented as median (quartile) and compared by non-parametric test, and categorical variables were presented as number (percentage) and compared by Chi-Squared test. Binary logistic regression analyses were performed to assess the association of nutritional status and gait performance with dementia, with Model 1 was adjusted for age and gender, and Model 2 was further adjusted for age of onset, educational level, and the scores of NPI and ADL scale based on Model 1. Pearson correlation analysis and Spearman correlation analysis were performed to evaluate the correlations between nutritional status and gait performance in the total patients, the AD-MCI group and the AD-D group, respectively, and presented by heat maps.