Abstract Whether extracellular water (ECW) increases with aging in humans and whether it is negatively associated with muscle function remains unclear. We aimed to clarify the associations of segmental intracellular water (ICW) and ECW with age and their independent associations with muscle strength and physical performance. This cross‐sectional analysis included 1102 older adults; segmental ECW and ICW in the thigh and arm were assessed by bioelectrical impedance spectroscopy (BIS). Knee extension and handgrip strength assessed muscle strength, and the timed‐up‐and‐go test, 6‐m maximum walk time, chair stand, vertical jump, and single‐leg balance tests assessed physical performance. Among older age groups, covariate‐adjusted thigh ECW was higher, whereas ICW and total body water were lower. Arm measures demonstrated similar age‐related patterns, although less consistently, with sex‐specific variation. Higher thigh and arm ECW levels were independently and negatively associated with muscle strength and physical performance in the corresponding segment (thigh: |β| = 0.12–0.31; arm: |β| = 0.12–0.20) after covariate adjustment. Conversely, higher arm and thigh ICW levels were positively associated with muscle strength and physical performance in the corresponding segment after adjustment. ICW may reflect functional muscle, whereas ECW may not be merely a passive non‐contractile compartment; rather, it may be a negative correlate of muscle strength and physical performance. Assessing segmental ECW alongside ICW may be essential to detect age‐related differences in muscle quality.

The escalating effects of climate change, particularly global warming, are posing an increasing burden on human health. Older adults are particularly susceptible to the impact of extreme heat. Adequate water intake is essential to prevent dehydration in hot environments. Therefore, it is important to understand water turnover (WT) and intake. WT of older adults in hot environments remains unknown. This study aimed at investigating the seasonal effects on WT, total energy expenditure (TEE), and physical activity using doubly labeled water (DLW) and a triaxial accelerometer. A total of 26 older Japanese adult males and females aged ≥ 65 years participated in the study. WT and TEE were measured using DLW in May and August 2012. The mean values of maximum, mean, and minimum temperatures and mean humidity of the measurement days were 24 °C, 19 °C, 14 °C, and 57% in May (spring) and 35 °C, 29 °C, 25 °C, and 66% in August (summer) 2012, respectively. The mean (standard deviation, SD) age of the participants was 73.7 (5.4) years. Total body water increased significantly from 31.1 (4.6) to 31.9 (5.2) kg (+ 0.8 kg, P = 0.009) from May to August. TEE decreased significantly from 2271 (280) to 2123 (470) kcal/day (- 149 kcal/d, P = 0.036), while WT increased significantly from 2.939 (0.625) to 3.579 (0.943) L/day (+ 0.640 L/d, P < 0.001). WT increased by 640 mL/day during summer compared to that during spring, when the average temperature was 19 °C. Our findings indicate that WT increases during hot weather in older adults, reflecting seasonal adaptation.

Purpose Diet influences frailty, and protein intake has been a prime focus of prevention. However, frailty remains prevalent, even among older adults with relatively high protein intake, suggesting the influence of remaining energy distribution between carbohydrates and fat. We investigated the association of the carbohydrate-to-fat energy ratio (CFr) with comprehensive frailty in older Japanese adults and the influence of protein intake. Methods Cross-sectional baseline data from 5,679 community-dwelling adults aged ≥ 65 years in the Kyoto–Kameoka Study were analyzed. Diet was assessed using a validated 46-item food-frequency questionnaire. Percent energy from carbohydrates, fat, and protein was calculated. CFr was defined as the ratio of percent energy from carbohydrates to that from fat. Frailty was defined as a Kihon Checklist score ≥ 7. Multivariate logistic regression estimated odds ratios (ORs) and 95% confidence intervals for frailty across CFr quartiles, adjusting for sociodemographic, lifestyle, and health-related factors. Restricted cubic splines assessed overall dose–response and within sex-specific tertiles of protein intake. Results Frailty prevalence was 36%. Compared with the lowest CFr quartile, adjusted ORs for frailty in the second, third, and highest quartiles were 1.14, 1.45, and 2.02, respectively. Spline models showed little association at lower CFr values, with risk increasing at higher ratios. Higher CFr was consistently associated with greater frailty prevalence within low-, middle-, and high-protein tertiles, and formal tests showed no effect modification by protein intake. Conclusion A higher CFr is associated with a higher prevalence of comprehensive frailty in older Japanese adults, with broadly similar associations across protein-intake levels.

Sarcopenia, defined as age-related muscle loss, has significant implications on the physical performance and health of older adults. An adequate dietary protein intake plays a crucial role in maintaining muscle mass and function. In Japan, the “Take 10!” assessment method, focusing on 10 food groups with an emphasis on 5 protein-rich foods, has been used for older adults. This study aimed to explore the relationship between the protein-rich food intake frequency score (PFFS) and muscle mass, strength, muscle-specific strength, and physical performance in older Japanese women. This study included 309 Japanese women aged 65–92 years. The appendicular skeletal muscle mass and skeletal muscle index were assessed. Hand grip strength and knee extension strength were measured, and muscle-specific strength was calculated. Chair stand test, shuttle stamina walk test, 10-m walk test, and timed up-and-go test were conducted. The Take 10 food frequency score (Take10-FFS) and PFFS were obtained. A one-way analysis of covariance was conducted, adjusted for age, percent body fat, exercise habits, smoking habits, alcohol habits, preexisting conditions, polypharmacy, fall incidence within 1 year, subjective economic status, and years of education. Higher Take 10-FFS and PFFS were associated with better muscle mass, strength, and physical performance (P < 0.05), emphasizing the importance of protein intake in preventing sarcopenia. However, no direct association was found between PFFS and muscle-specific strength (P > 0.05). This underscores the complexity of the factors influencing muscle-specific strength.

Muscle volume, strength, physical performance, and quality (functional and morphological domains) decline with age; however, the specific patterns and differences among these variables in old age remain unclear. We quantitatively assessed sex- and age-related changes and differences among these variables in older adults. We hypothesized that the rates of age-related decline differ among the parameters. Specifically, muscle quality would decline more steeply than muscle mass, with sex-related variations. A cross-sectional survey of 1370 community-dwelling Japanese older adults (aged 65-90 years) was conducted. Muscle mass and volume were measured by appendicular lean mass (ALM) index using bioelectrical impedance spectroscopy (BIS) and thigh muscle thickness (MT) using ultrasonography. Physical performance was assessed by the 5-times chair stand, timed up-and-go test, maximum walking speed, and vertical jump × body weight. Handgrip strength (HG) and knee extension strength (KES) were used to assess muscle strength. Functional (HG/ALM and KES/MT) and morphological (whole-body and thigh phase angles [PhA], extracellular/intracellular water ratio [ECW/ICW] by BIS, and thigh echo intensity by ultrasonography) domain muscle qualities were assessed. Linear regression predicted significant age-related declines in all parameters. The predicted decline rates/year were as follows: thigh MT (male: 0.9 %; female: 1.1 %), KES (male: 2.0 %; female: 2.1 %), lower extremity physical performance (male: 1.4-2.8 %; female: 1.8-3.0 %), thigh morphological muscle quality via BIS (male: 1.5-2.2 %; female: 1.4-1.9 %), echo intensity (male: 1.2 %; female: 0.5 %), and functional muscle quality (KES/MT) (male: 1.3 %; female: 1.3 %). The slopes of lower extremity strength, performance, and muscle quality were steeper than those of muscle mass. These patterns also varied by parameter and sex. This study provides novel insight into the differential aging patterns of muscle mass, strength, performance, and functional (e.g., KES/MT) and morphological (e.g., PhA, ECW/ICW, EI) muscle quality by simultaneously comparing age- and sex-related changes in these parameters. Our findings highlight muscle quality, particularly in the lower limbs, as a sensitive and distinct indicator of age-related physical decline. These findings offer new perspectives for assessing and intervening with older adults.

BACKGROUND:Muscle quality, along with muscle mass, deteriorates with disuse, ageing and various disorders, underscoring the need to evaluate the internal characteristics of swallowing-related muscles. Previous studies have reported an association between oral function and echo intensity (EI), but the association between oral function and the stiffness of swallowing-related muscles, as well as the degree of this association, remains insufficiently understood. OBJECTIVE:To examine the association between oral function and the intramuscular characteristics of swallowing-related muscles, focusing on muscle stiffness. MATERIALS AND METHODS:A total of 196 older women (78.1 ± 5.2 years) participated in a physical fitness measurement session in this cross-sectional study. The stiffness and EI of the geniohyoid muscle (GHM) were measured, and oral function was evaluated using oral diadochokinesis (ODK; /pa/, /ta/, /ka/) and tongue pressure. Multiple regression analysis was used to investigate the association between oral function, stiffness and EI. By standardising the variables, we evaluated these associations independently of the units. RESULTS:ODK, /pa/ (β = -0.144, p = 0.002), /ta/ (β = -0.134, p = 0.011) and /ka/ (β = -0.093, p = 0.043) showed a negative association with GHM stiffness. After standardisation, the association between ODK (/pa/, /ta/, /ka/) and GHM stiffness (β: -0.144, -0.134, -0.093) was comparable to that between ODK and EI (β: -0.008, -0.148, -0.075). CONCLUSION:GHM stiffness was associated with oral motor function in older women living in the community. Assessing the stiffness of swallowing-related muscles could be important for evaluating oral function to a degree comparable to EI.

BACKGROUND:The interaction and substitution effects of physical activity (PA) and sitting time (ST) living in non-western countries have not been well investigated. This study aimed to examine the association of moderate-to-vigorous physical activity (MVPA) and ST with disability and mortality in older adults. METHODS:This prospective study analyzed data from 10,164 adults aged over 65 years who participated in the Kyoto-Kameoka study in Japan. We evaluated MVPA and ST using the validated International Physical Activity Questionnaire-Short Form. Participants were categorized into four groups based on their levels of MVPA (150 min/week) and ST (300 min/day): low MVPA/high ST, low MVPA/low ST, high MVPA/high ST, and high MVPA/low ST. Outcomes were gathered between July 30, 2011, and November 30, 2016. RESULTS:Over a median follow-up of 5.3 years (45,461 person-years), 2,273 disability cases were documented. The low MVPA/high ST groups were associated with higher disability risk than those in the high MVPA/low ST groups (hazard ratio [HR] 1.52; 95% confidence interval [CI], 1.31-1.75), and the interaction between MVPA and ST accounted for 48.5% of the relative excess risk of disability in the low MVPA/high ST group (P for interaction = 0.006). Daily replacement of 10 minutes of ST with 10 minutes of MVPA was associated with a reduced risk of disability (HR 0.980; 95% CI, 0.971-0.989) and all-cause mortality (HR 0.975; 95% CI, 0.962-0.988). CONCLUSION:These findings indicate that even a small substitution of ST with MVPA could help lower both the risk of disability and mortality.

The SARC-F is a 5-item questionnaire screening for patients at risk of sarcopenia. The electrical properties of tissues derived from bioelectrical impedance spectroscopy (BIS), including phase angle (PhA) and intracellular-extracellular water ratio (ICW/ECW) indices, are biomarkers of age-related loss of skeletal muscle quantity and quality. The purpose of the current study was to examine the association between SARC-F and muscle mass, strength, muscle-specific strength, and muscle quality as assessed by BIS and hand grip strength (HGS). Sarcopenia risk was assessed using the SARC-F questionnaire. BIS was used to obtain skeletal muscle mass (SMM) and skeletal muscle mass index (SMI), PhA, ICW/ECW index, membrane capacitance (Cm) and characteristic frequency (fc) for assessing muscle quantity and quality. HGS was evaluated, and muscle-specific strength (HGS/SMM) was calculated. The Pearson correlation coefficient was used to examine the associations between SARC-F scores and each muscle parameter. A total of 205 older adults aged 65–99 years were included in the current cross-sectional analysis. Of those, 142 were community-dwelling healthy older adults (110 women and32 men) and 63 were the older adults living in special nursing homes for the older adults (45 women and 18 men). SARC-F was significantly correlated with SMM, SMI, HGS, and HGS/SMM in both men and women (p < 0.05). SARC-F was also correlated with PhA, ICW/ECW index, Cm, and fc in both men and women (p < 0.001). The SARC-F score was associated with SMM, HGS, HGS/SMM, PhA, ICW/ECW index, Cm, and fc independently of age, sex, height, and BMI. SARC-F is a subjective yet simple assessment tool for muscle mass, strength, and quality relevant to sarcopenia.

In 2024, we launched the Osaka-Settsu Prospective Cohort Study for Health, Nutrition and Well-being (the Osaka-Settsu Study) in Japan. This population-based prospective study aimed to identify the risk factors for lifestyle-related diseases and care given and contribute to precision health care. This cohort profile paper describes the study design and the demographics of the participants. A self-administered questionnaire survey was mailed to registered residents aged ≥ 18 years in Settsu City from February to June 2024. The survey asked the participants about physical activity, nutritional status, well-being, and frailty. The participants will be followed up for the incidence of lifestyle-related diseases, need for support/long-term care certification, emergency transportation, and migration. Of the 71,680 self-administered questionnaires distributed, 13,282 were completed. There were 7238 females and 5887 males. Mean age (standard deviation) were 62.1 (17.6) and 60.7 (18.4) years for females and males, respectively. The number of participants was highest in 70-79 year age group for both female and male participants. The body mass index tends to increase with age in female, in contrast, that increased with age, peaked in the 50s, and declined thereafter in male. This study is planned to collect information on vital status and conducts follow-up surveys to identify the predictors of functional decline across the course of life. This study provides valuable evidence for the development of strategies to extend a healthy lifespan.

Background:Total daily energy expenditure (TDEE) is vital for energy balance and cardiometabolic health, yet its trajectory across the lifespan, particularly in females, remains poorly understood. Objectives:We sought to examine the effects of aging and sex on body composition and TDEE. Methods:In a cross-sectional analysis of data from research centers across 9 European Countries and the United States from the International Atomic Energy Agency database, TDEE and body composition measures of 2326 participants (1560W/766M; 50.7 ± 12 .6 y) were stratified across age groups: young (30-39 y; YOUNG), middle-aged (40-54 y; MID), and old (55-70 y; OLD). Doubly labeled water was used to estimate TDEE and fat-free mass (FFM). Fat mass (FM) was calculated as the difference between body mass and FFM, and %fat was ratio between FM and body mass as a percentage. Linear models were used for analysis. Results:Females demonstrated greater FM and lower FFM with each age group, compared with males (P < 0.001). In females, OLD had lower absolute TDEE than YOUNG (-217 kcal/d, P < 0.001) and MID (-208 kcal/d, P < 0.001). Male absolute TDEE was lowered across all age groups (OLD compared with YOUNG: -334 kcal/d; OLD compared with MID: -210 kcal/d; MID compared with YOUNG: -124 kcal/d; P < 0.001). Adjusted TDEE was similar within age groups between females and males. Conclusions:These results suggest that age influences changes in body composition and energy expenditure similarly between males and females. The most significant change in TDEE occurs as individuals transition from middle age to older adulthood. Females generally have a higher percentage of %fat and FM, along with lower FFM, compared with males across all age groups. These findings are important for understanding how aging affects metabolism and body composition, which could inform sex-specific health strategies and interventions.

BACKGROUND & AIMS:Although phase angle at 50 kHz (PhA50) is widely used, its validity relative to the theoretically correct characteristic-frequency PhA (PhAcf) remains unclear. This study evaluated the validity of the PhA50 by comparing it with the PhAcf and examining its associations with body composition, muscle strength, and physical function. METHODS:This cross-sectional study included 1266 community-dwelling older adults. Bioimpedance spectroscopy (BIS) was used to assess whole-body, thigh, and arm impedance parameters. PhAcf, PhA50, membrane capacitance (Cm), extracellular water (ECW), intracellular water (ICW), total body water (TBW), and ECW/ICW ratio were derived. Muscle strength (grip strength and knee extension) and physical function (Timed Up-and-Go test, 6-m walk, 5-times chair stand, and vertical jump) were assessed. RESULTS:Characteristic frequency was positively associated with age, whereas PhA50 and PhAcf were negatively associated with age. PhA50 was strongly correlated with PhAcf and ECW/ICW (|r|>0.90), with Cm (|r|>0.70), and with ICW and TBW (|r|>0.40) across segments in both sexes. Both PhA50 and PhAcf were significantly associated with muscle strength and physical function, and no significant differences were observed in the correlation coefficients between the two PhA measures for muscle strength and physical function. Thigh PhA (both PhA50 and PhAcf) showed significantly stronger correlations with lower extremity muscle strength and performance than arm PhA. CONCLUSIONS:The commonly used PhA50 closely approximates PhAcf and ECW/ICW and reflects Cm, ICW, and TBW. PhA50 could assess muscle strength and physical function with similarity to the theoretically optimal yet harder-to-measure PhAcf. These findings support PhA50 as a practical index for clinical nutrition research and potential healthcare screening.

Nutritional epidemiology aims to link dietary exposures to chronic disease, but the instruments for evaluating dietary intake are inaccurate. One way to identify unreliable data and the sources of errors is to compare estimated intakes with the total energy expenditure (TEE). In this study, we used the International Atomic Energy Agency Doubly Labeled Water Database to derive a predictive equation for TEE using 6,497 measures of TEE in individuals aged 4 to 96years. The resultant regression equation predicts expected TEE from easily acquired variables, such as body weight, age and sex, with 95% predictive limits that can be used to screen for misreporting by participants in dietary studies. We applied the equation to two large datasets (National Diet and Nutrition Survey and National Health and Nutrition Examination Survey) and found that the level of misreporting was >50%. The macronutrient composition from dietary reports in these studies was systematically biased as the level of misreporting increased, leading to potentially spurious associations between diet components and body mass index.

Background:The socioeconomic impact of the COVID-19 pandemic has severely affected individuals' mental health. However, the factors that mitigate or exacerbate the mental health effects of economic deterioration remain underexplored. Objective:This paper analyzes survey data from the second wave of the COVID-19 pandemic in Japan, a period during which women workers were reported to be economically and psychologically vulnerable. The analysis examined factors that mitigate or amplify the impact of COVID-19-induced economic deterioration on mental health, testing 3 hypotheses based on the conservation of resources theory and the stress buffering model: the negative impact of economic deterioration on mental health is greater for individuals with less social support compared to those with more social support (hypothesis 1); the negative impact of economic deterioration on mental health is greater for individuals experiencing more negative interactions compared to those experiencing fewer (hypothesis 2); and the buffering effect of social support is stronger in women than in men, with women receiving less social support experiencing greater mental health impacts from economic deterioration (hypothesis 3). Methods:A web-based survey was conducted by an internet research company in Japan from June to July 2020. A balanced sample of 250 men and 250 women was recruited from each of the following age groups: 20-29, 30-39, 40-49, 50-59, 60-69, and 70-79 years. The analysis focused on working men and women aged 20-50 years (n=1238). Psychological distress was measured using the K6 scale. Economic deterioration was defined as a decrease in income compared to the prepandemic levels, and scales for social support and negative interactions were included. Logistic regression analysis was performed, using K6≥9 as the dependent variable, with interaction terms for each hypothesis sequentially incorporated. Results:In the best-fitting model determined by the Bayesian Information Criterion, a significant association was observed between the interaction of COVID-19-induced economic deterioration and social support with K6 scores (odds ratio [OR] 0.90, 95% CI 0.81-0.99). However, in other models, the interaction between economic deterioration and negative interactions (OR 1.01, 95% CI 0.90-1.13) as well as the 3-way interaction involving economic deterioration, social support, and gender (OR 1.13, 95%CI 0.92-1.39) were not significant. The average marginal effect of economic deterioration was statistically significant for social support scores ranging from 4 to 10. The average marginal effect was 0.11 when social support was 4 (95% CI 0.03-1.20; P=.009) and 0.028 when social support was 10 (95% CI 0.00-0.06; P=.047). Conclusions:The adverse impact of economic deterioration on mental health was more pronounced among individuals with lower levels of social support. These findings support hypothesis 1.

Several epidemiological studies have shown that consumption of coffee and green tea is inversely associated with risks of death and disability; however, the relationship between caffeine consumption and these outcomes remains unclear. We examined these associations in Japanese older adults. This was a prospective study of 7708 adults (aged ≥ 65 years) recruited from the Kyoto-Kameoka study. Dietary intake was estimated using a validated FFQ. Caffeine consumption was classified into four categories. Disability and mortality data were collected between 15 February 2012 and 30 November 2016. Hazard ratios (HR) and 95 % CI of outcomes were calculated using multivariable Cox proportional hazard models. During the median 4·75-year follow-up period, a total of 593 deaths and 1379 disability incidents were recorded. After adjusting for confounders, caffeine consumption was inversely associated with the incidence of disability (< 100 mg/d: reference; 100-149 mg/d: HR, 0·91 (95 % CI 0·80, 1·04); 150-199 mg/d: HR, 0·84 (95 % CI 0·72, 0·99); ≥ 200 mg/d: HR, 0·75 (95 % CI 0·63, 0·89), Pfor trend = 0·001) but not all-cause mortality. High coffee consumption was inversely associated with mortality (≥ 3 cups/d: HR, 0·62 (95 % CI 0·43, 0·88)) and disability (≥ 3 cups/d: HR, 0·81 (95 % CI 0·65, 0·99)) compared with non-consumption. However, green tea consumption was not associated with mortality or disability. Caffeine and coffee consumption was inversely associated with disability and/or mortality. Further research is needed to clarify whether high caffeine intake is safe and effective for older adults.

BACKGROUND:Previous epidemiological studies have revealed a relationship among planetary health diets (PHDs), diet-related greenhouse gas emissions (GHGEs), and mortality. However, these studies did not include older adults from non-Western countries. This study examined these associations in Japanese older adults. METHODS:This prospective study included 8, 043 adults aged ≥65 years from the Kyoto-Kameoka study in Japan. Dietary intake was estimated using a validated food frequency questionnaire. Adherence to PHDs was evaluated by calculating the EAT-Lancet index (range, 0 [worst] to 42 [best]), which were classified into 4 categories: ≤25 (n = 1 061; very low), 26-27 (n = 1 703; low), 28-30 (n = 3 368; moderate), and ≥31 (n = 1,911; high) points. Diet-related GHGEs were calculated using previously developed GHGE tables for each food item. RESULTS:During the median 4.75-year follow-up period, 659 deaths and 1 431 incidents of functional disability were recorded. After adjusting for confounders, the hazard ratios of mortality were lower in the moderate-adherence group than in the very low-adherence group (hazard ratio, 0.64; 95% confidence interval; 0.60-0.93). Planetary health diet scores tended to be inversely associated with functional disability (p for trend = .081). However, diet-related GHGEs were not associated with mortality or disability. The PHD score ranges with the lowest hazard ratios for mortality and mean diet-related GHGE were 28-30 and 29-31 points, respectively. CONCLUSIONS:Moderate adherence to current PHD is inversely associated with diet-related GHGE and mortality risk. This underscores the importance of dietary shifts for improving public health and environmental sustainability.

PURPOSE:This study aimed to determine the associations between the phase angle (PhA), extracellular water-to-intracellular water ratio (ECW/ICW), physical activity levels (PALs) measured using the doubly labeled water (DLW) method, and the time spent engaging in physical activities of varying intensities in older adults living in Japan. METHODS:This study was part of the Kyoto-Kameoka prospective cohort study of older adults. The PhA and ECW/ICW ratio were measured using a multi-frequency bioelectrical impedance analysis device. PAL, percentage body fat, and fat-free mass index were calculated using the DLW method, while the average daily moderate-to-vigorous physical activity (MVPA), high-intensity light physical activity (HLPA), low-intensity light physical activity, and sedentary behavior durations were quantified using a triaxial accelerometer. RESULTS:Adjusted partial order correlation analysis showed significant positive correlations between the PhA and PAL (p = 0.001), as well as between the PhA and the MVPA (p = 0.027) and HLPA (p = 0.023) durations. The PAL was also significantly negatively correlated with the ECW/ICW ratio (p = 0.008). Adjusted multiple regression analysis confirmed that PAL (p = 0.004) and HLPA (p = 0.025) were significantly positively associated with PhA and negatively associated with ECW/ICW ratio (p = 0.004 and p = 0.036, respectively). CONCLUSIONS:PAL, measured using the precise DLW method, is an explanatory factor for PhA and ECW/ICW ratio. HLPA below the MVPA threshold was linked to more favorable hydration markers of cellular health in older adults. As this was a cross-sectional study, causality cannot be inferred.

We investigated the associations between red blood cell (RBC) count, hemoglobin (Hb) levels, muscle properties, and muscle strength in community-dwelling older adults, and examined whether RBC count and Hb levels were linked to muscle strength through muscle mass and/or quality, and whether these relationships were influenced by physical activity. The study included 85 community-dwelling older adults (39 males; mean age 75.3 ± 6.7 years). The participants visited the laboratory in the morning for venous blood sampling to analyze blood biomarkers. Quadriceps femoris muscle thickness (MT, muscle mass index) and echo intensity (EI, muscle quality index) were measured via B-mode ultrasonography, and maximum isometric knee extension strength was assessed using a dynamometer. The average daily step count was recorded for 2 weeks as an index of physical activity. Correlation and mediation analyses were used to investigate the associations between blood biomarkers and muscle properties, strength, and physical activity. The RBC count and Hb levels were positively correlated with MT and muscle strength, and negatively correlated with EI. After adjusting for age and sex, the correlations between RBC count, Hb levels, and MT and muscle strength remained significant, whereas the associations with EI disappeared. In the mediation analyses, the direct effect of RBC count and Hb levels on muscle strength was not significant, whereas the indirect effect of MT was, regardless of whether physical activity was adjusted. In community-dwelling older adults, lower RBC counts and Hb levels appear to be associated with diminished muscle mass, potentially resulting in muscle weakness.

Background/Objectives: Frailty is a multifactorial condition influenced by physical and psychosocial factors. Understanding longitudinal changes in these domains may guide prevention strategies. This study examines the relationship between frailty status, physical fitness, and psychosocial conditions in community-dwelling older adults using five-year longitudinal data. Methods: Participants were 52 out of 89 older adults who completed both baseline and five-year follow-up assessments (follow-up rate: 58.4%). Data were collected using 10 physical fitness indicators, the fitness age score (FAS), geriatric depression scale (GDS), Lubben social network scale short form (LSNS-6), and relevant items in the six Kihon Checklist (KCL) domains. Due to low prevalence of frailty, individuals with pre-frailty and frailty were combined into the frailty-risk group. Repeated measures ANOVA with sex as a covariate was conducted to compare groups. Logistic regression was used to identify baseline predictors of frailty status at five years. Statistical significance was set at p < 0.05. Results: GDS, LSNS-6, and KCL scores remained stable over five years. However, physical fitness significantly declined in several measures, including grip strength, vertical jump height, knee extension strength, functional reach, and FAS. A significant interaction for the timed up and go test showed that the robust group maintained function, while the frailty-risk group declined. Logistic regression identified KCL oral function as a significant predictor (OR = 5.331, 95% CI = 1.593-17.839, p = 0.007). Conclusions: Maintaining both oral function and physical fitness is vital for preventing frailty, even among health-conscious older adults. Proactive strategies may support healthy aging.