Abstract
[Purpose] Effective nutritional management is essential for inpatient rehabilitation. This study aimed to examine changes in body composition in relation to weight gain or loss between admission and discharge from convalescent rehabilitation wards. [Participants and Methods] A total of 91 patients (39 men and 52 women) admitted to convalescent rehabilitation wards were included. Body composition, height, and weight were measured during admission and discharge using a device which allows measurements in seated or supine positions (InBody S10). Patients were classified into three groups based on whether they gained, maintained, or lost at least 3% of their body weight. [Results] Thirteen participants (six men and seven women) were categorized into the weight gain group, 58 (24 men and 34 women) into the unchanged group, and 20 (nine men and 11 women) into the weight loss group. Significant differences in the percentage change in the amount of body fat in men and change in the skeletal muscle mass index in women were observed. [Conclusion] In men, changes in body fat mass were observed, while in women, skeletal muscle mass changes were observed, which were linked to weight variations. These findings underscore the gender-specific differences in body composition changes during inpatient rehabilitation.
Keywords: Body composition, Convalescent rehabilitation wards, Weight change rate
INTRODUCTION
The importance of appropriate management of patients admitted to convalescent rehabilitation wards is increasing with an aging society. In the Japanese healthcare system, convalescent rehabilitation wards provide intensive rehabilitation to patients who have undergone acute care, facilitating their return to home and social life. Specifically, patients who experience conditions such as strokes and proximal femur fractures are classified into medical treatment categories, primarily based on the rate of return to home and improvement in activities of daily living1, 2). Convalescent rehabilitation wards, considered the cornerstone of rehabilitation medicine, act as important intermediate facilities that bridge the acute phase of care with home-based care.
Nutritional management of patients is essential during rehabilitation: 12.4% of men and 20.7% of women over 65 years of age tend to be undernourished (body mass index [BMI], ≤20 kg/m2); additionally, 30–50% of hospitalized patients are reported undernourished3, 4). The diagnosis of undernutrition includes assessment of changes in body weight, necessitating regular monitoring.
Furthermore, in hospitalized patients, changes in body composition have attracted attention as indicators of physical function and nutritional status. Particularly, phase angle (PhA) and skeletal muscle index (SMI) are considered important predictors of prognosis in such patients; however, few longitudinal studies have explored the relationship between sex and weight variations in patients admitted to convalescent rehabilitation wards. This study aimed to clarify the relationship between changes in body composition and weight at admission and discharge in patients admitted to convalescent rehabilitation wards.
PARTICIPANTS AND METHODS
This is a longitudinal observational study conducted at a single institution. Ninety one patients (39 men, mean ± standard deviation age 73.2 ± 11.5 years; 52 women, mean ± standard deviation age 80.9 ± 10.1 years) who were admitted to the convalescent rehabilitation ward of the International University of Health and Welfare, Shioya Hospital between August 2021 and December 2022.
Measurements included assessments of height, weight, and body composition performed within 2 weeks after admission and before discharge. Height was measured using a measuring tape in those who were unable to stand. Weight was measured before assessments of body composition. BMI was calculated using the measured weight and height. Body composition was measured using a multifrequency bioimpedance device (InBody S10; InBody, Tokyo, Japan) and included evaluations of body fat mass, PhA, SMI, and the ratio of extracellular water to total body water. This device can be used in supine or seated positions, making it ideal for patients who are unable to stand or sit because of severe functional impairments5, 6).
The exclusion criteria were as follows: patients who did not provide consent to their attending physicians for the measurements, those with implanted electronic medical devices such as pacemakers, and those wearing life-support devices such as biometric monitors.
Based on weight at the time of admission, rates of weight change at the time of discharge were calculated, and participants were classified into the weight gain, weight unchanged, and weight loss groups accordingly. Since the criteria “more than 3% weight loss in 1 to 6 months” is used for the diagnosis of undernutrition7), the same cut-off value was used herein for the categorization of the participants. Patients with increases in weight of ≥3.0% were categorized into the weight gain group; those with weight changes ranging from an increase of 2.9% to a decrease of 2.9% were categorized into the weight unchanged group; and those with decreases in weight of ≥3.0% were categorized into the weight loss group. Similarly, percentage changes were calculated for each body composition item, and Kruskal–Wallis tests were performed with weight change as a factor, and the Tamhane-T2 tests were performed as a subtest. All statistical analyses were performed using SPSS Statistics version 29 (IBM, Armonk, NY, USA). Statistical significance was set at the level of 5%.
The study was conducted in accordance with the Declaration of Helsinki 1964 and its subsequent revisions. The aims and procedures of the study were explained to the participants or their families and informed consent was obtained. This study was approved by the Ethics Review Committee of the International University of Health and Welfare (approval no. 21-Io-13).
RESULTS
Herein, 13 participants were categorized into the weight gain group (six men and seven women), 58 into the weight unchanged group (24 men and 34 women), and 20 in the weight loss group (nine men and 11 women) (Tables 1, 2). For men, 21 were in neurosurgery, eight in neurology, and 10 in orthopedics, while for women, 11 were in neurosurgery, eight in neurology, and 33 in orthopedics. Among the groups, men showed significant differences in percentage change in body fat mass (weight gain group: +22.9 [−27.1 to 30.2]%; weight unchanged group: +0.5 [−11.9 to 39.4]%; weight loss group: −7.6 [−25.5 to 4.1]%, median [minimum–maximum]) (p<0.05). Conversely, among the groups, women showed significant differences in percentage change in SMI (weight gain group: +5.3 [−13.0 to 37.3]%; weight unchanged group: +0.8 [−20.5 to 19.1]%; weight loss group: −7.4 [−20.6 to 6.4]%) (p<0.05) (Table 3).
Table 1. Characteristics and measurement results of the men.
| Men, n=39 | Tamhane-T2 test | |||
| Weight gain group (G) n=6 |
Weight unchanged group (U) n=24 |
Weight loss group (L) n=9 |
||
| Age (years) | 78.5 (44.0 to 92.0) | 74.0 (55.0 to 92.0) | 75.0 (50.0 to 86.0) | |
| Height (cm) | 160.0 (140.8 to 169.7) | 165.7 (149.0 to 180.0) | 165.0 (153.2 to 174.0) | |
| Weight (kg) | ||||
| Admission* | 44.1 (41.2 to 59.5) | 59.6 (46.2 to 83.5) | 61.5 (54.5 to 80.0) | G vs. U *, G vs. L * |
| Discharge | 48.0 (43.8 to 62.5) | 60.0 (46.5 to 83.7) | 57.1 (52.7 to 77.4) | |
| BMI (kg/m2) | ||||
| Admission* | 18.9 (16.1 to 21.5) | 21.8 (16.8 to 27.3) | 21.6 (20.1 to 26.6) | G vs. L * |
| Discharge | 20.2 (17.1 to 22.7) | 21.7 (16.8 to 27.3) | 21.2 (19.4 to 27.3) | |
| Body fat mass (kg) | ||||
| Admission* | 10.4 (7.4 to 19.2) | 15.8 (7.5 to 31.8) | 18.5 (11.2 to 26.5) | G vs. L * |
| Discharge | 13.3 (9.4 to 16.5) | 16.2 (8.2 to 31.7) | 14.2 (10.2 to 27.3) | |
| PhA (°) | ||||
| Admission | 3.5 (2.3 to 4.5) | 4.4 (2.9 to 8.0) | 4.3 (2.9 to 5.4) | |
| Discharge | 3.6 (2.6 to 4.5) | 4.4 (3.0 to 7.7) | 4.3 (3.1 to 5.4) | |
| SMI (kg/m2) | ||||
| Admission* | 5.4 (4.6 to 6.7) | 6.8 (5.2 to 8.5) | 6.4 (5.2 to 8.0) | G vs. U * |
| Discharge | 5.7 (4.7 to 6.8) | 6.7 (5.1 to 8.5) | 6.6 (5.2 to 8.7) | |
| ECW/TBW | ||||
| Admission | 0.413 (0.392 to 0.421) | 0.398 (0.371 to 0.418) | 0.402 (0.390 to 0.417) | |
| Discharge | 0.410 (0.397 to 0.416) | 0.397 (0.370 to 0.434) | 0.402 (0.383 to 0.427) | |
Data are presented as median (minimum–maximum). BMI: body mass index; PhA: phase angle; SMI: skeletal muscle index; ECW/TBW: the ratio of extracellular water to total body water. Kruskal–Wallis test; * indicates p<0.05. Tamhane-T2 test; * indicates p<0.05.
Table 2. Characteristics and measurement results of the women.
| Women, n=52 | Tamhane-T2 test | |||
| Weight gain group (G) n=7 |
Weight unchanged group (U) n=34 |
Weight loss group (L) n=11 |
||
| Age (years) | 82.0 (55.0 to 94.0) | 82.0 (50.0 to 92.0) | 86.0 (69.0 to 96.0) | |
| Height (cm) | 152.0 (133.0 to 159.4) | 147.9 (130.2 to 161.1) | 148.0 (136.9 to 158.0) | |
| Weight (kg) | ||||
| Admission | 45.6 (36.7 to 56.5) | 48.8 (30.3 to 70.4) | 46.0 (35.3 to 78.9) | |
| Discharge | 47.0 (39.0 to 58.5) | 48.3 (30.2 to 72.2) | 44.3 (29.7 to 76.0) | |
| BMI (kg/m2) | ||||
| Admission | 20.3 (15.6 to 25.7) | 22.8 (15.5 to 30.8) | 20.1 (14.6 to 37.5) | |
| Discharge | 20.9 (16.6 to 26.6) | 22.8 (15.5 to 31.6) | 19.3 (13.2 to 34.7) | |
| Body fat mass (kg) | ||||
| Admission | 11.6 (7.0 to 20.3) | 17.2 (4.3 to 32.7) | 14.3 (5.7 to 42.1) | |
| Discharge | 14.7 (6.9 to 21.9) | 18.2 (4.2 to 33.0) | 12.9 (0.9 to 39.3) | |
| PhA (°) | ||||
| Admission | 3.3 (2.3 to 4.7) | 3.7 (2.1 to 4.9) | 3.5 (2.3 to 5.1) | |
| Discharge | 3.4 (1.7 to 6.2) | 3.7 (1.9 to 5.0) | 3.5 (2.7 to 4.6) | |
| SMI (kg/m2) | ||||
| Admission | 5.4 (4.3 to 6.1) | 5.3 (3.0 to 7.8) | 5.6 (4.7 to 6.3) | |
| Discharge | 5.7 (4.2 to 7.3) | 5.3 (3.4 to 6.9) | 5.0 (4.8 to 6.2) | |
| ECW/TBW | ||||
| Admission | 0.415 (0.397 to 0.418) | 0.414 (0.395 to 0.433) | 0.412 (0.360 to 0.447) | |
| Discharge | 0.414 (0.373 to 0.432) | 0.411 (0.390 to 0.424) | 0.415 (0.391 to 0.433) | |
Data are presented as median (minimum–maximum). BMI: body mass index; PhA: phase angle; SMI: skeletal muscle index; ECW/TBW: the ratio of extracellular water to total body water. Kruskal–Wallis test; * indicates p<0.05. Tamhane-T2 test; * indicates p<0.05.
Table 3. Percentage changes in body composition items (%).
| Weight gain group (G) | Weight unchanged group (U) | Weight loss group (L) | Tamhane-T2 test | |
| Men | ||||
| Body fat mass* | 22.9 (−27.1 to 30.2) | 0.5 (−11.9 to 39.4) | −7.6 (−25.5 to 4.1) | G vs. L *, U vs. L * |
| PhA | 9.4 (−8.9 to 17.9) | 0.0 (−24.4 to 19.4) | 0.0 (−17.6 to 13.2) | |
| SMI | 3.2 (−6.8 to 19.3) | 0.0 (−5.0 to 6.5) | −2.5 (−9.9 to 35.9) | |
| ECW/TBW | −0.6 (−1.3 to 1.4) | 0.0 (−1.2 to 8.8) | −0.3 (−2.0 to 4.7) | |
| Women | ||||
| Body fat mass | 5.0 (−39.5 to 12.9) | 2.0 (−24.0 to 43.9) | −12.8 (−47.4 to 14.7) | |
| PhA | 2.6 (−26.1 to 31.9) | 2.7 (−15.6 to 33.3) | 5.1 (−19.6 to 26.1) | |
| SMI* | 5.3 (−13.0 to 37.3) | 0.8 (−20.5 to 19.1) | −7.4 (−20.6 to 6.4) | G vs. L *, U vs. L * |
| ECW/TBW | 0.5 (−7.0 to 3.3) | −0.7 (−2.1 to 1.9) | −0.7 (−5.1 to 10.6) |
Data are presented as median (minimum–maximum). PhA: phase angle; SMI: skeletal muscle index; ECW/TBW: the ratio of extracellular water to total body water. Kruskal–Wallis test; * indicates p<0.05. Tamhane-T2 test; * indicates p<0.05.
DISCUSSION
The results of this study revealed that in patients admitted to convalescent rehabilitation wards, changes in body weight were associated with changes in body composition, which differed according to sex. Men were significantly affected by changes in body fat mass, whereas women were primarily affected by changes in SMI.
Generally, men have a greater accumulation of visceral fat, which plays a major role in energy storage and metabolic regulation8, 9). An energy imbalance during rehabilitation might directly affect the amount of body fat mass, particularly visceral fat. In addition, because men have a higher basal metabolic rate and expend more energy than women, the effects of exercise therapy and nutritional management regarding fat metabolism may be more pronounced. Furthermore, strength training and aerobic exercise during rehabilitation may create a metabolic environment conducive for lipolysis.
Conversely, in women, weight fluctuations were associated with changes in skeletal muscle mass. As women generally possess lower muscle mass than men, the effects of rehabilitation interventions aimed at muscle restructuring may be more pronounced. In older women, an appropriate exercise load promotes muscle protein synthesis and contributes to increased skeletal muscle mass10,11,12). Furthermore, estrogen plays an important role in skeletal muscle metabolism and repair, and its influence is thought to persist, to some extent, in older women. This may reflect weight gain during rehabilitation with an increase in SMI.
This study has some limitations. The lack of dietary intake data hindered the assessment of energy and nutrient consumption, making it difficult to identify factors influencing body composition and nutritional status. Similarly, the absence of blood data, such as D-dimer levels, limited the evaluation of the relationship between nutrition, inflammation, and thrombotic risk. Furthermore, the effectiveness of interventions may vary between chronically and acutely ill patients due to their differing nutritional and metabolic needs, and changes in disease status during hospitalization must also be considered. Future interventions aimed at improving nutritional status and overall health are needed.
The results of this study suggest that interventions accounting for sex-specific changes in body composition are important in the management of patients admitted to convalescent rehabilitation wards. In men, body fat mass tends to fluctuate more than muscle mass with aging and disease, and excessive fat accumulation is a significant risk factor for sarcopenic obesity. Therefore, it is important to regularly monitor body fat mass and maintain an appropriate energy balance. Specifically, nutritional management should focus on ensuring adequate protein intake while reducing excessive caloric consumption. Additionally, a program that combines aerobic exercise with strength training is effective in preserving muscle mass and optimizing body fat levels. In contrast, women experience a significant decline in muscle mass due to aging and disease, with hormonal changes potentially accelerating muscle atrophy. Therefore, rehabilitation interventions aimed at maintaining and increasing muscle mass are essential. Specifically, in addition to actively incorporating resistance training, a high-protein diet and nutritional supplementation rich in essential amino acids are recommended. Proper management of vitamin D and calcium intake is also crucial to prevent the deterioration of skeletal muscle function. This study provides valuable insights to support the development of gender-specific rehabilitation programs.
Funding
This study was supported by JSPS KAKENHI (grant numbers: 21K10581 and 24K23756).
Conflicts of interest
The authors have no conflicts of interest relevant to the content of this article.
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