Association of smoking cessation with dynapenia among older lifetime smokers in Korea.

INTRODUCTION: Muscle strength is known to play an important role in the health of older adults. The health burden of cigarette smoking among older adults remains significant. We investigated the association between smoking cessation and dynapenia among older lifetime smokers in Korea. METHODS: This study is a secondary dataset analysis of cross-sectional data from theKorea National Health and Nutrition Examination Survey (KNHANES) 2016- 2019. We included 1450 participants aged 65-79 years, excluding those who had never smoked. Dynapenia was defined as grip strength <28 kg for men and <18 kg for women based on the Asian Working Group for Sarcopenia 2019 criteria. Multivariable logistic regression analysis evaluated the association between smoking cessation and dynapenia. RESULTS: Compared with current smokers, the adjusted odds ratio (AOR) of dynapenia in former smokers was 0.66 (95% CI: 0.44-0.99). The AORs for smoking cessation periods of ≤10 years, 10-20 years, 20-30 years, and >30 years were 0.67 (95% CI: 0.39-1.16), 0.61 (95% CI: 0.36-1.03), 0.65 (95% CI: 0.37-1.14), and 0.52 (95% CI: 0.25-1.06), respectively. The AOR for dynapenia significantly decreased with the years since smoking cessation (p for trend=0.043). CONCLUSIONS: Our findings suggest that smoking cessation can reduce the likelihood of dynapenia among older lifetime smokers, with a decreasing likelihood trend associated with longer cessation periods.

Association Between Dynapenia, Central Obesity, and Physical Function in Young Adults: A Cross-Sectional Study.

BACKGROUND: Muscle strength is recognized as a key indicator of overall health and can help identify the risk of cardiometabolic disease. This study explores the relationship between low muscle strength, central obesity, and physical function among young adults. METHODS: We conducted a cross-sectional study from a convenience sample of 513 adults aged 18-25. Participants' anthropometric measures such as height, weight, and circumferences of both waist and hip were measured, and body mass index (BMI) was calculated. Subjects were tested for hand grip strength (HGS) using hand dynamometry. Relative hand grip strength (RHGS) was derived by dividing maximum HGS by BMI. Physical function was assessed using a six-minute walk test. The International Physical Activity Questionnaire (IPAQ) was administered. RESULTS:  Overweight and obesity were present in 313 (61%) of the study population. Central obesity was observed in 194 (37.8%) of the population. RHGS showed a positive association with physical function and physical activity, and a negative association was observed with BMI and waist circumference. Low RHGS was categorized as < 25th percentile by gender. The non-dynapenic non-central obese group had higher physical function (644± 124.2) than others. There was no difference in the dynapenic and central obese groups. The dynapenic central obese group had significantly lesser physical function (424.9±69.1) than all other groups in both genders. CONCLUSION: Our study supports the importance of early investigation of dynapenia, which can increase the risk of chronic disease and accelerate the development of physical limitations. Understanding how dynapenia and central obesity relate to low physical function is of growing importance in young adults, and it can play an important role in overall health.

Osteoporosis as the Female-Specific Risk Factor for Dynapenia in Elderly Patients with Type 2 Diabetes.

Aims: Dynapenia is a noteworthy health issue contributing to increased risk of falling, but its co-occurrence with osteoporosis in elderly individuals with type 2 diabetes mellitus (T2DM) has not been well explored. Therefore, this study aimed to establish the association between osteoporosis and dynapenia, focusing on T2DM females due to their high prevalence of osteoporosis and fragility. Methods: We conducted a cross-sectional study to recruit a total of 103 T2DM patients (43 males and 60 females), aged between 50 and 80 years with median 68.0 years. Dual-energy X-ray absorptiometry (DXA) and dominant hand grip strength measurements were performed to define body composition, osteoporosis, and dynapenia in a sex-specific manner. Results: Higher prevalence of dynapenia and dyna-osteoporosis was observed in female T2DM patients with a significantly positive correlation between osteoporosis and dynapenia even after adjustment of body mass index (BMI). By performing a multivariate logistic regression analysis, both BMI and osteoporosis were identified as risk predictors for the development of dynapenia in female T2DM patients with odds ratios (95% CIs) of 1.234 (1.029-1.480) and 4.883 (1.352-17.630), respectively. Conclusions: Our results point out there is high, female-specific co-occurrence of osteoporosis and dynapenia in T2DM patients. Moreover, having osteoporosis and increased BMI might boost the risk of dynapenia in elderly females with T2DM.

Prevalence and Risk Factors for Hand-Grip-Determined Dynapenia in the Korean Population: A Cross-Sectional Study.

Dynapenia refers to muscle weakness related to aging and is defined as a loss of muscle strength associated with muscle quality. The purpose of this study is to identify the prevalence of dynapenia and associated risk factors by gender and age in domestic adults and to provide customized basic data for the prevention of dynapenia through its management. Based on the data from 2014 to 2019 of the Korea National Health and Nutrition Survey, 20,950 adults over the age of 20 who participated in grip strength tests and health surveys were selected as participants. Factors related to dynapenia were analyzed using complex sample multilogistic regression analysis. The prevalence of dynapenia in domestic adults was 6.3%, 4.1% in men, and 8.7% in women. Prevalence in the second decade was 5.3%, in the third decade was 3.2%, in the fourth decade was 3.3%, in the fifth decade was 4.8%, in the sixth decade was 8.9%, and was 24.6% for participants in their seventh decade or beyond. Among the factors related to dynapenia, age, BMI, and alcohol status were common in both men and women; education level, HDL-C, and resistance exercise were common in men; and high blood pressure, high blood sugar, and aerobic exercise were common in women. Our findings indicate that several factors are associated with dynapenia, which should be considered as potential targets for interventions focused on both individual and public health measures.

The role of dynapenia and obesity on cognitive function in older adults.

BACKGROUND & AIMS: Dynapenia and obesity have been independently associated with cognitive decline in older adults, but their co-occurring effects has not been well-studied. The study objective is to examine the relationship between dynapenic-obesity and cognitive impairment in older adults 75 years and older with normal or high cognitive function at baseline over 12 years of follow-up. We hypothesize that those with dynapenic obesity will have greater odds of cognitive function impairment than those with dynapenia only, obesity only, or no dynapenia no obesity (reference group). METHODS: A total of 761 participants with a mean age of 81.5 and Mini-Mental State Examination (MMSE) > 21 at baseline were divided into four groups: no dynapenia no obesity (n = 316), obesity only (n = 142), dynapenia only (n = 217), and dynapenic obesity (n = 86). Measures included socio-demographics, medical conditions, body mass index, depressive symptoms, handgrip strength, and limitations in activities of daily living. We performed a mixed models estimate for cognitive decline for these groups over a 12-year period. Handgrip strength (HGS) was measured with a handgrip dynamometer and cognitive function was assessed with MMSE. RESULTS: Participants in the dynapenia-obesity group experienced a greater (ß = - 1.29, Standard Error = 0.60, p-value = 0.0316) cognitive decline over time compared to those in the no dynapenia and no obesity group, after controlling for all covariates. CONCLUSION: Older adults with dynapenic-obesity were at high risk of cognitive decline over time. These findings highlight the need for interventions that target both conditions in this population to help maintain cognitive health. Community-based strength training programs and educational initiatives on nutrition and diet can help older adults reduce their risk of age-related cognitive decline.

Athletic Performance Decline Over the Life Span: Cross-Sectional and Longitudinal Analyses of Elite and Masters Track-and-Field Data.

PURPOSE: Loss of muscle power has a significant impact on mobility in geriatric populations, so this study sought to determine the extent and time course of performance decline in power-centric events throughout the life span via retrospective analyses of masters and elite track-and-field data. METHODS: Four track-and-field events were selected based on maximal power output: the 100-m dash, long jump, high jump, and triple jump. Elite and masters athlete data were gathered from the World Masters Outdoor Championships and the International Amateur Athletic Federation World Athletics Championships (17,945 individual results). Data were analyzed by fitting individual and group results to quadratic and linear models. RESULTS: Average age of peak performance in all events was 27.8 (0.8) years for men and 28.3 (0.8) years for women. Athlete performance decline best matched a linear model for the 5 years following peak performance (mean R2 = .68 [.20]) and for ages 35-60, but best matched a quadratic model for ages 60-90 and 35-90 (mean R2 = .75 [.12]). The average rate of decline for the masters data ages 35-60 ranged from 0.55% per year for men's 100-m dash to 1.04% per year for women's long jump. A significant age × sex interaction existed between men and women, with men declining faster throughout life in all events except the 100-m dash. CONCLUSIONS: Performance decline begins in the early 30s and is linear through middle age. This pattern of decline provides a basis for further research on power-decline pathophysiology and preventive measures starting in the 30s.

Age, sex, and APOE gene-specific associations between dynapenic obesity and dementia in a large cohort.

OBJECTIVE: To investigate the associations between dynapenic obesity and the risk of dementia, and the modifying effects of age, sex, and the APOE gene, using a large population-based cohort. METHODS: 279,884 participants aged 55 and above from the UK Biobank were included. The participants were classified into four categories based on body mass index and hand grip strength: healthy, obesity, dynapenia, and dynapenic obesity. The incident dementia was identified based on linked hospital records and death register data. Cox proportional hazards regression models were used to estimate the associations, followed by age-, sex-, and apolipoprotein E (APOE) gene-stratified analyses. RESULTS: During the median follow-up of 12.4 years, 5,170 (1.8%) participants developed dementia. Compared with the healthy group, participants with dynapenic obesity had 67% higher dementia risk (hazard ratio [HR]: 1.67, 95% confidence interval [CI]: 1.44-1.94). Compared with the healthy group, higher risks of dementia in participants with dynapenic obesity were respectively observed in male (HR: 2.03, 95% CI: 1.65-2.50), younger (<65 years, HR: 1.97, 95% CI: 1.55-2.50), and non-ε4-carrier (HR: 1.97, 95% CI: 1.60-2.44) (all P for interaction <0.05). In participants under 65 years and non-ε4-carrier, those with dynapenic obesity had the highest risk of dementia (HR: 2.63, 95% CI: 1.91-3.62), compared with the healthy group (P for second order interaction = 0.026). CONCLUSIONS: Dynapenic obesity is associated with increased risks of dementia, especially in participants under 65 years and non-ε4-carrier, suggesting the importance of managing dynapenic obesity in the prevention of cognition-related disorders.

Dynapenia and sarcopenia identify walking speed decline in women but not in men.

OBJECTIVE: To determine the best indicator of mobility decline between dynapenia, low skeletal muscle mass index (SMMI), and sarcopenia defined by the EWGSOP2 using different cutoff points for grip strength. METHODS: A longitudinal study was conducted with a follow-up of eight years, involving 2,680 individuals aged 60 and older who participated in the ELSA study with a walking speed greater than 0.8 m/s at baseline. Dynapenia was defined using different cutoff points for grip strength. SMMI was defined by the 20th percentile of the entire ELSA sample distribution and sarcopenia was defined based on the EWGSOP2, using different cutoff points for grip strength. Mobility was analysed using the walking speed test. RESULTS: Over time, the greatest decline in walking speed occurred in dynapenic women with grip strength < 17 kg (-0.005 m/s per year; 95 % CI: -0.01 to -0.001) and < 20 kg (-0.007 m/s per year; 95 % CI: -0.01 to -0.001). With regards to sarcopenia, the greatest walking speed decline occurred in women with probable sarcopenia when defined by grip strength < 17 kg [(-0.006 m/s per year; 95 % CI: -0.01 to -0.001) or grip strength < 20 kg (-0.007 m/s per year; 95 % CI: -0.01 to -0.001)]. Dynapenia in men as well as low SMMI and sarcopenia in men and women did not enable identifying the risk of mobility decline. CONCLUSION: Dynapenia and probable sarcopenia defined by grip strength < 17 kg and < 20 kg enabled identifying walking speed decline over time only in women.

Positive impact of obesity on the prognosis of liver cirrhosis.

BACKGROUND AND AIM: The study aims to determine the prognostic impact of obesity, sarcopenic obesity, and dynapenic obesity in patients with chronic liver disease. METHODS: This retrospective observational study enrolled patients with chronic hepatitis (n = 746) and liver cirrhosis (n = 434) without hepatocellular carcinoma at entry. The patients were evaluated for sarcopenia and obesity between April 2016 and April 2022. Obesity was defined as a body mass index of ≥ 25 kg/m2. Sarcopenic obesity was defined as low skeletal muscle mass (pre-sarcopenia) with obesity and dynapenic obesity was defined as low muscle strength (dynapenia) with obesity. The effects of obesity on survival were evaluated retrospectively. RESULTS: The mean observation period was 2.5 years. Obesity, sarcopenic obesity, and dynapenic obesity were found in 271 (45.5%), 17 (2.9%), and 21 (3.5%) men, and 261 (44.7%), 59 (10.1%), and 53 (9.1%) women, respectively. A multivariate Cox proportional hazards model revealed that Child-Pugh class, dynapenia (hazard ratio [HR] 3.89), elderly (≥ 65 years old) (HR 2.11), and obesity (HR 0.58) were independently associated with overall survival (OS). However, neither sarcopenic nor dynapenic obesity were associated with OS. In patients with cirrhosis, the OS of the obese group was significantly higher than that of the non-obese group. The effect of obesity on OS was significant in elderly patients, but not in younger patients. CONCLUSIONS: Sarcopenic and dynapenic obesity seem unrelated to the prognosis of patients with chronic liver disease. Obesity has a positive effect on the prognosis of elderly patients with cirrhosis.

Task-specific resistance training adaptations in older adults: comparing traditional and functional exercise interventions.

Muscle strength declines ∼3% per year after the age of 70. Resistance training guidelines for older adults are often based on free-weight and machine exercises, which may be inaccessible and lack carryover to activities of daily living. We tested the hypothesis that resistance training adaptations in older adults are task-specific. Thirty adults (8 males, 22 females; mean age = 71 years) were randomly assigned to participate in 6 weeks of supervised, high-intensity resistance training (twice per week) utilizing free-weight and machine exercises (traditional) versus functional activities that were overloaded with a weighted vest (functional). Participants were thoroughly familiarized with the exercises and testing prior to beginning the study. Major outcome measures included assessments of functional performance, five-repetition maximum strength, isometric knee extensor force, and quadriceps muscle size. Physical activity and nutrition were monitored. The study results demonstrate that the magnitude of improvement within a given outcome was largely dependent on group assignment, with greater improvements in gait speed and the timed-up-and-go in the functional group, but 2-3× greater five repetition maximum strength improvements for the trap bar deadlift, leg press, and leg extension following traditional resistance training. Both groups showed improvements in isometric knee extensor force and muscle size, suggesting that some aspects of the observed adaptations were generic, rather than specific. Overall, these novel findings suggest that, among older adults, 1) resistance training adaptations exhibit a high degree of task specificity and 2) significant improvements in functional outcomes can be achieved with the use of a weighted vest.

Association between dynapenia and multimorbidity: A systematic review.

Dynapenia and multimorbidity are common health problems affecting older adults. However, few studies have systematically reviewed the association between dynapenia and multimorbidity. Therefore, this systematic review aimed to provide a comprehensive overview of studies on the association between these conditions. We searched four electronic databases for relevant articles published in July 2023. The main inclusion criteria were the following: (1) a description of dynapenia, which indicates loss of muscle strength and (2) a description of multimorbidity with two or more chronic diseases. Five studies met these inclusion criteria. In all five of these studies, the participants were community-dwelling older adults. All the studies showed an association between dynapenia and multimorbidity. The prevalence of dynapenia and multimorbidity ranged from 16% to 25.9%. The results of our systematic review demonstrated that dynapenia in older adults increases the risk of multimorbidity. We propose that interventions and reversible changes in dynapenia can prevent multimorbidity.

Initial handgrip strength as a predictive factor for amputation risk in diabetic foot patients.

BACKGROUND: We aimed to analyze the prognostic significance of handgrip strength as predictor of lower extremity amputation at 1 year follow up in patients with type 2 diabetes. METHODS: We evaluated 526 patients with type 2 diabetes between August 2020, and, June 2022. We collected from the electronic medical records demographic variables, laboratory data and history of amputation. The handgrip strength was assessed using a handheld Smedley digital dynamometer following the NHANES Muscle Strenght/Grip Test Procedure. Low handgrip strength was defined for women as less than 16 kg and for men less than 27 kg. Outcome variable was major or minor lower extremity amputation. RESULTS: A total of 205 patients with complete data entered the study. Patients mean age was 59 years old, 37% were women and the mean diabetes disease duration was 14 years. Seventy-seven (37%) patients suffered from lower extremity mputations (26 major and 51 minor amputations). After controlling for age, gender, presence of peripheral artery disease, body mass index and white cell counts as confounder variables, patients with low handgrip had an increased risk for amputations (Odds Ratio 2.17; 95% confidence Interval: 1.09-4.32; <0.001). CONCLUSION: Low handgrip stregth is an independent prognostic marker for lower limb amputation at one year in patients with diabetes.

Dynapenic abdominal obesity and incident functional disability: Results from a nationwide longitudinal study of middle-aged and older adults in China.

BACKGROUND: There is little epidemiological evidence on the relationship of dynapenic abdominal obesity (DAO) and the development of functional disability, particularly in Asian populations. We aimed to investigate the association of DAO with new-onset functional disability in Chinese adults. METHODS: A total of 7881 participants aged ≥45 years from China Health and Retirement Longitudinal Study (CHARLS) in 2011 and 2015 were included in the study. Dynapenia and abdominal obesity were respectively defined based on handgrip strength (<28 kg for male and <18 kg for female) and waist circumference (≥ 90 cm for male and ≥85 cm for female). The sample was divided into four groups: non-dynapenic/non-abdominal obesity (ND/NAO), non-dynapenic/abdominal obesity (ND/AO), dynapenic/non-abdominal obesity (D/NAO) and dynapenic/abdominal obesity (D/AO). Functional status was assessed by basic activities of daily living (BADL) or instrumental activities of daily living (IADL). Logistic regression model was used to explore the longitudinal association between dynapenic abdominal obesity and incident functional disability. RESULTS: After a 4-year follow-up, 1153 (14.6 %) developed BADL disability and 1335 (16.9 %) developed IADL disability. The multivariable-adjusted odds ratios (95 % CIs) for the D/AO versus ND/NAO were 2.21 (1.61-3.03) for BADL disability, and 1.68 (1.23-2.30) for IADL disability. In addition, DAO was associated with an increased risk for functional dependency severity (odds ratio, 2.08 [95 % CI, 1.57-2.75]). CONCLUSIONS: DAO was significantly associated with greater risk of functional disability among Chinese middle-aged and older adults. Our findings indicated that interventions targeted DAO might be effective in the primary prevention of functional disability.

Sex Differences in the Impact of Dynapenic Abdominal Obesity on Mild Cognitive Impairment among Korean Elderly in the Community.

Abdominal obesity (AO) and dynapenia (DP) are associated with cognitive decline, and the relationship between dynapenic abdominal obesity (DAO), a combination of DP and AO, and mild cognitive impairment (MCI) has been confirmed. This study aims to determine whether this relationship exhibits potential sex differences. The relationship between MCI and DAO was confirmed in 1309 community elderly individuals aged 65 years or older who were not diagnosed with dementia. The MCI was defined as a Korean mini-mental state examination (K-MMSE) score of 18-23 points. Multiple logistic regression analyses were conducted, categorizing participants into groups: a control group without AO or DP, an AO group, a DP group, and a DAO group. The study results showed that in women, both DP and DAO were significantly associated with MCI not only in the unadjusted Model 1 but also in Model 2, which adjusted for general characteristics and health behaviors, and Model 3, which additionally adjusted for chronic diseases and disease-related characteristics. In men, DP was associated with MCI in the unadjusted Model 1. The findings highlight sex differences in the impact of the DAO on MCI. These differences should be considered when studying the factors related to MCI in old age.

Powerpenia Should be Considered a Biomarker of Healthy Aging.

To identify biomarkers that precede the decline of human function and independence during the lifespan, two important concepts have been introduced in recent decades: sarcopenia and dynapenia. While the former is originally focused on skeletal muscle loss, the latter is on maximal strength loss. Although the dynapenia concept implies the inclusion of skeletal muscle power, in practical terms, this has not been specifically addressed. For instance, only 2 out of 220 studies published between 2008 and 2023 have directly measured muscle power to classify individuals with dynapenia. As previous studies have shown a greater relevance of skeletal muscle power in healthy aging, we hereby propose the introduction of the term "powerpenia" to specifically reflect the loss of skeletal muscle power along lifespan, but also with disease and/or physical inactivity. Together with sarcopenia and dynapenia, we contend that powerpenia should be considered a biomarker of healthy aging.

Relationship between Eating Alone and Handgrip Strength in Korean Older Adults.

Sarcopenia is defined as an age-related decline in muscle mass, muscle strength, and physical performance. Eating alone has been linked to various health issues in older adults. This study investigated the relationship between eating alone and handgrip strength (HGS) in older adults using data from 7278 individuals (≥65 years) who participated in the 2014-2019 Korea National Health and Nutrition Examination Survey. HGS was measured using a digital grip strength dynamometer, relative HGS was calculated by dividing HGS by body mass index, and dynapenia was defined as an HGS < 28 kg for men and <18 kg for women. Multivariable logistic regression analysis showed that women who ate two meals alone were more likely to exhibit dynapenia than those who never ate alone (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.03-1.77). If the groups that never ate alone or ate one meal alone were combined as the reference group, the probability of dynapenia was higher in the combined groups that ate two or three meals alone (OR, 1.25; 95% CI, 1.04-1.50). No association was observed between eating alone and dynapenia in men. This suggests that eating alone is a modifiable related factor of dynapenia in older women.

Assessing muscular power in older adults: evaluating the predictive capacity of the 30-second chair rise test.

Background: Timed chair rise tests are frequently used as a substitute for assessing leg muscle strength or power. To determine if timed chair rise tests are an indicator of lower extremity muscle power, we examined the relationship between the repetitions completed in a 30-s chair rise test and the power generated during the test. Methods: Seventy-five individuals participated in this study (n = 30 < 65 years and 45 ≥ 65 years). Participants underwent a 30-s chair rise test while instrumented with a power analyzer. Handgrip strength was also evaluated. Results: The relationship between chair rise repetitions and average chair rise power was R 2 = 0.32 (p < 0.001). Chair rise repetitions when regressed on a total (i.e., summed) chair rise power, it yielded R 2 = 0.70 with data from all participants combined (p < 0.001). A mediation analysis indicated that anthropometrics partially mediates the relationship between chair rise repetitions and total chair rise power accounting for 2.8%-6.9% of the variance. Conclusion: Our findings indicate that in older adults, the overall performance of chair rises offers limited information about the average power per rise but is more indicative of the cumulative power exerted. Thus, the total number of chair rises in a 30-s test is likely a more comprehensive metric of overall muscular power, reflecting endurance aspects as well. Additionally, we found that personal physical attributes, such as height and weight, partially influence the link between chair rise count and total power, highlighting the importance of factoring in individual body metrics in assessments of muscular performance.

Association between bone health and dynapenic obesity in postmenopausal women.

AIM: The combination of dynapenia (age-related muscle weakness) and obesity is referred to as dynapenic obesity. We examined the associations between dynapenic obesity and cortical bone thickness and trabecular bone density. METHODS: The participants were 797 community-dwelling postmenopausal women (with an average age of 62.5 years) who were stratified into normopenia without obesity, dynapenia without obesity (dynapenia), normopenia with obesity (obesity) and dynapenia with obesity (dynapenia obesity) groups based on their grip strength and body fat percentage. Cortical bone thickness and trabecular bone density were measured using ultrasonic bone densitometry. The participants were further divided into those with low cortical bone thickness and low trabecular bone density. Logistic regression analysis was used to identify associated factors. RESULTS: Individuals with dynapenia (odds ratio [OR] 1.77, 95% confidence interval [CI] 1.16-2.68), obesity (OR 2.46, 95% CI 1.62-3.75) and dynapenic obesity (OR 4.07, 95% CI 2.44-6.79) all significantly increased the odds of low cortical bone thickness. Conversely, the odds of low trabecular bone density were significantly lower in the obesity group (OR 0.65, 95% CI 0.43-0.99) and dynapenic obesity group (OR 0.60, 95% CI 0.37-0.97). CONCLUSIONS: Dynapenic obesity was found to be associated with cortical bone thinning that might compromise bone health. Postmenopausal women with dynapenic obesity might need to be closely monitored for preserving bone health. Geriatr Gerontol Int 2024; 24: 378-384.

Precision MRI phenotyping of muscle volume and quality at a population scale.

Introduction: Magnetic resonance imaging (MRI) enables direct measurements of muscle volume and quality, allowing for an in-depth understanding of their associations with anthropometric traits, and health conditions. However, it is unclear which muscle volume measurements: total muscle volume, regional measurements, measurements of muscle quality: intermuscular adipose tissue (IMAT) or proton density fat fraction (PDFF), are most informative and associate with relevant health conditions such as dynapenia and frailty. Methods: We have measured image-derived phenotypes (IDPs) including total and regional muscle volumes and measures of muscle quality, derived from the neck-to-knee Dixon images in 44,520 UK Biobank participants. We further segmented paraspinal muscle from 2D quantitative MRI to quantify muscle PDFF and iron concentration. We defined dynapenia based on grip strength below sex-specific cut-off points and frailty based on five criteria (weight loss, exhaustion, grip strength, low physical activity and slow walking pace). We used logistic regression to investigate the association between muscle volume and quality measurements and dynapenia and frailty. Results: Muscle volumes were significantly higher in male compared with female participants, even after correcting for height while, IMAT (corrected for muscle volume) and paraspinal muscle PDFF were significantly higher in female compared with male participants. From the overall cohort, 7.6% (N = 3,261) were identified with dynapenia, and 1.1% (N = 455) with frailty. Dynapenia and frailty were positively associated with age and negatively associated with physical activity levels. Additionally, reduced muscle volume and quality measurements were associated with both dynapenia and frailty. In dynapenia, muscle volume IDPs were most informative, particularly total muscle exhibiting odds ratios (OR) of 0.392, while for frailty, muscle quality was found to be most informative, in particular thigh IMAT volume indexed to height squared (OR = 1.396), both with p-values below the Bonferroni-corrected threshold (p<8.8×10-5). Conclusion: Our fully automated method enables the quantification of muscle volumes and quality suitable for large population-based studies. For dynapenia, muscle volumes particularly those including greater body coverage such as total muscle are the most informative, whilst, for frailty, markers of muscle quality were the most informative IDPs. These results suggest that different measurements may have varying diagnostic values for different health conditions.

Prevalence and factors associated with dynapenia among middle-aged and elderly people in rural southern China.

To estimate the prevalence of dynapenia and examine potential risk factors for dynapenia using a sample of rural middle-aged and elderly Chinese. A cross-sectional study of 253 Chinese adults aged 50 years and older was conducted from June to August in 2022 in Nanjing. A questionnaire was used to collect data on all socioeconomic variables. Body weight, height, body fat percentage, grip strength, waist circumference, calf circumference, and gait speed were measured. The prevalence of dynapenia was 69.6 %, 62.3 % in men and 72.7 % in women respectively. Binary logistic regressions indicated significant associations between dynapenia and age (odds ratio [OR] = 2.59; 95 % confidence interval [CI] 1.63, 4.12; p < 0.001), educational level (OR = 0.55; 95 % CI 0.38, 0.80; p = 0.002). Dynapenia was prevalent among rural middle-aged and elderly people in southern China. Age and lower education level were both associated with dynapenia. Nutrition and physical activity should be strongly recommended as important strategies to maintain and improve muscle strength.