Muscle weakness and functional limitations in an ethnically diverse sample of older adults.

Objectives: Muscle weakness is often linked to functional limitations in older adults. However, certain demographic characteristics, such as ethnicity, may differentially impact the association between weakness and functional limitations. This investigation sought to (1) identify sex- and ethnically-specific muscle weakness thresholds associated with functional limitations among older adults, and (2) determine the odds of functional limitations for each ethnicity by sex after identifying older adults below the weakness thresholds.Design: Persons aged ≥60 years from the 2011-2012 to 2013-2014 waves of the National Health and Nutrition Examination Survey identifying as non-Hispanic white, non-Hispanic black, Hispanic, or non-Hispanic Asian were included. Handgrip strength was normalized to each participant's body weight (normalized grip strength (NGS)). Participants responded to 19-items asking them about their ability to perform certain activities of daily living, instrumental activities of daily living, leisure and social activities, lower extremity mobility functions, and general physical activities. Receiver operating characteristic curves identified the optimal NGS thresholds associated with functional limitations. Covariate-adjusted multiple logistic regression models were performed to determine the odds of functional limitations for weak vs. not-weak participants.Results: Of the 3,027 participants, the highest NGS thresholds for functional limitations were in non-Hispanic Asian males (0.41; p < 0.001) and Hispanic females (0.36; p < 0.001); whereas, the lowest NGS thresholds were in Hispanic males (0.25; p < 0.001) and non-Hispanic black females (0.23; p < 0.001). Weak non-Hispanic Asian males (odds ratio (OR): 10.42; 95% confidence interval (CI): 10.24, 10.61) and females (OR: 11.95; CI: 11.71, 12.19) had the highest odds for functional limitations compared to their non-weak counterparts.Conclusion: Preserving muscle strength, especially for certain older adult populations, may help reduce the odds of developing functional limitations. Interventions designed to increase muscle strength to preserve or improve function should consider the role of ethnicity when designing such interventions and identifying at risk populations.

Lack of Association Between Vitamin D and Hand Grip Strength in Asians: A Nationwide Population-Based Study.

Despite the beneficial role and plausible mechanism of vitamin D on skeletal muscle in animal studies, its association in humans remains a controversial issue due to inconsistent clinical results, especially in older Asians. This was a population-based, cross-sectional study from the Korea National Health and Nutrition Examination Surveys, which enrolled 354 men aged ≥ 50 years and 328 postmenopausal women. Hand grip strength (HGS) was measured using a digital grip strength dynamometer. Low muscle strength was defined based on Korean-specific cut-off point of HGS. Serum 25-hydroxyvitamin D [25(OH)D] levels were 19.4 ± 6.7 and 17.1 ± 7.2 ng/mL in men and women, respectively. Among covariates including age, body mass index, lifestyle factors, and protein intake, age was inversely associated with HGS in both men and women, and protein intake (g/day) was positively associated with HGS only in men. However, the independent correlation between serum 25(OH)D and HGS was not observed, regardless of gender. When subjects were divided into three groups [deficient (25(OH)D < 20 ng/mL; 63.8%), insufficient (20 ≤ 25(OH)D < 30 ng/mL; 30.0%), or sufficient (25(OH)D ≥ 30 ng/mL; 6.2%)], there was no significant difference in HGS among these groups in both men and women. Consistently, serum 25(OH)D was not significantly different between subjects with and without low muscle strength, and there was no independent association of serum 25(OH)D with the risk of low muscle strength in both genders. These findings provide clinical evidence that protective role of vitamin D on human muscle metabolism may not be evident at least in older Asians.

Differences in the prevalence of sarcopenia in haemodialysis patients: the effects of gender and ethnicity.

BACKGROUND: There is no universal consensus definition of sarcopenia, although there is agreement that sarcopenia is a risk factor for mortality in haemodialysis (HD) patients. We aimed to determine the effect of using different operational definitions in a multiracial group of HD patients. METHODS: We measured hand grip strength (HGS) and appendicular lean mass (ALM) by segmental bioimpedance using the Foundation for the National Institutes of Health Sarcopenia Project (FNIH), European Working Group on Sarcopenia (EWGS) and Asian Working Group on Sarcopenia definitions for HGS weakness and loss of appendicular lean mass. RESULTS: In total, there were 600 HD patients: 373 men (62.2%), mean (SD) age 66.3 (14.7) years, 45.6% diabetic, ethnicity: 281 (48.5%) White, 167 (27.8%) Asian and 149 (24.8%) Black. On HGS criteria, 90.5% of Asian women and 88.5% of Asian men were weak according to EWGS compared to 62.3% of Black women and 52.5% of Black men and 64.5% of White women and 69.1% of White men by FNIH criteria (P < 0.001). On adding appendicular lean mass, the prevalence of sarcopenia was 68.3% for Asian, 27.1% for Black and 36.6% for White women by FNIH and 59.6% Asian, 21.3% Black and 39.9% White men by EWGS criteria. CONCLUSIONS: Current definitions of sarcopenia report a greater prevalence of muscle weakness compared to appendicular muscle loss in female compared to male HD patients and this is greater for Asian compared to Black and White patients. Because HGS weakness is a greater risk for death, definitions of sarcopenia may underestimate risk in HD patients.

Association between grip strength and diabetes prevalence in black, South-Asian, and white European ethnic groups: a cross-sectional analysis of 418 656 participants in the UK Biobank study.

AIMS: To quantify the extent to which ethnic differences in muscular strength might account for the substantially higher prevalence of diabetes in black and South-Asian compared with white European adults. METHODS: This cross-sectional study used baseline data from the UK Biobank study on 418 656 white European, black and South-Asian participants, aged 40-69 years, who had complete data on diabetes status and hand-grip strength. Associations between hand-grip strength and diabetes were assessed using logistic regression and were adjusted for potential confounding factors. RESULTS: Lower grip strength was associated with higher prevalence of diabetes, independent of confounding factors, across all ethnicities in both men and women. Diabetes prevalence was approximately three- to fourfold higher in South-Asian and two- to threefold higher in black participants compared with white European participants across all levels of grip strength, but grip strength in South-Asian men and women was ~ 5-6 kg lower than in the other ethnic groups. Thus, the attributable risk for diabetes associated with low grip strength was substantially higher in South-Asian participants (3.9 and 4.2 cases per 100 men and women, respectively) than in white participants (2.0 and 0.6 cases per 100 men and women, respectively). Attributable risk associated with low grip strength was also high in black men (4.3 cases) but not in black women (0.4 cases). CONCLUSIONS: Low strength is associated with a disproportionately large number of diabetes cases in South-Asian men and women and in black men. Trials are needed to determine whether interventions to improve strength in these groups could help reduce ethnic inequalities in diabetes prevalence.

National women's knowledge of stroke warning signs, overall and by race/ethnic group.

BACKGROUND AND PURPOSE: Recognition of stroke warning signs may reduce treatment delays. The purpose of this study was to evaluate contemporary knowledge of stroke warning signs and knowledge to call 9-1-1, among a nationally representative sample of women, overall and by race/ethnic group. METHODS: A study of cardiovascular disease awareness was conducted by the American Heart Association in 2012 among English-speaking US women ≥25 years identified through random-digit dialing (n=1205; 54% white, 17% black, 17% Hispanic, and 12% other). Knowledge of stroke warning signs, and what to do first if experiencing stroke warning signs, was assessed by standardized open-ended questions. RESULTS: Half of women surveyed (51%) identified sudden weakness/numbness of face/limb on one side as a stroke warning sign; this did not vary by race/ethnic group. Loss of/trouble talking/understanding speech was identified by 44% of women, more frequently among white versus Hispanic women (48% versus 36%; P<0.05). Fewer than 1 in 4 women identified sudden severe headache (23%), unexplained dizziness (20%), or sudden dimness/loss of vision (18%) as warning signs, and 1 in 5 (20%) did not know 1 stroke warning sign. The majority of women said that they would call 9-1-1 first if they thought they were experiencing signs of a stroke (84%), and this did not vary among black (86%), Hispanic (79%), or white/other (85%) women. CONCLUSIONS: Knowledge of stroke warning signs was low among a nationally representative sample of women, especially among Hispanics. In contrast, knowledge to call 9-1-1 when experiencing signs of stroke was high.

Patterns and correlates of grip strength change with age in Afro-Caribbean men.

BACKGROUND: muscle strength is essential for physical functions and an indicator of morbidity and mortality in older adults. Among the factors associated with muscle strength loss with age, ethnicity has been shown to play an important role. OBJECTIVE: to examine the patterns and correlates of muscle strength change with age in a population-based cohort of middle-aged and older Afro-Caribbean men. METHODS: handgrip strength and body composition were measured in 1,710 Afro-Caribbean men. Data were also collected for demographic variables, medical history and lifestyle behaviours. RESULTS: the age range of the study population was 29-89 years. Grip strength increased below age 50 years, and decreased after age 50 years over 4.5-year follow-up. The average loss in grip strength was 2.2% (0.49% per year) for ages 50 years or older and 3.8% (0.64% per year) for ages 65 years or older. The significant independent predictors of grip strength loss included older age, a greater body mass index, lower initial arm lean mass and greater loss of arm lean mass. CONCLUSION: Afro-Caribbean men experience a significant decline in muscle strength with advanced age. The major independent factors associated with strength loss were similar to other ethnic groups, including age, body weight and lean mass.

Sarcopenia Definition & Outcomes Consortium Defined Low Grip Strength in Two Cross-Sectional, Population-Based Cohorts.

BACKGROUND/OBJECTIVES: The extent to which the prevalence of muscle weakness in the US population varies by different putative grip strength constructs developed by the Sarcopenia Definitions and Outcomes Consortium (SDOC) has not been described. DESIGN: Cross-sectional analysis. SETTING: Two nationally representative cohorts-2010 and 2012 waves of the Health and Retirement Survey and round 1 (2011) of the National Health and Aging Trends Survey. PARTICIPANTS: Adults aged 65 years and older (n = 12,984) were included in these analyses. MEASUREMENTS: We analyzed three constructs of muscle weakness developed by the SDOC, and found to be associated with mobility disability for men and women, respectively: absolute grip strength (<35.5 kg and 20 kg); grip strength standardized to body mass index (<1.05 kg/kg/m² and 0.79 kg/kg/m²); and grip strength standardized to weight (<0.45 kg/kg and 0.337 kg/kg). We estimated the prevalence of muscle weakness defined by each of these constructs in the overall older US population, and by age, sex, race, and ethnicity. We also estimated the sensitivity and specificity of each of the grip strength constructs to discriminate slowness (gait speed <0.8 m/s) in these samples. RESULTS: The prevalence of muscle weakness ranged from 23% to 61% for men and from 30% to 66% for women, depending on the construct used. There was substantial variation in the prevalence of muscle weakness by race and ethnicity. The sensitivity and specificity of these measures for discriminating slowness varied widely, ranging from 0.30 to 0.92 (sensitivity) and from 0.17 to 0.88 (specificity). CONCLUSIONS: The prevalence of muscle weakness, defined by the putative SDOC grip strength constructs, depends on the construct of weakness used. J Am Geriatr Soc 68:1438-1444, 2020.

Performance of maximum inspiratory pressure tests and maximum inspiratory pressure reference equations for 4 race/ethnic groups.

BACKGROUND: Maximum inspiratory pressure (MIP) is an important and noninvasive index of diaphragm strength and an independent predictor of all-cause mortality. The ability of adults over a wide age range and multiple race/ethnicities to perform MIP tests has previously not been evaluated. METHODS: The Multi-Ethnic Study of Atherosclerosis recruited white, African American, Hispanic, and Chinese American participants, ages 45-84 years, and free of clinical cardiovascular disease in 6 United States cities. MIP was measured using standard techniques among 3,849 Multi-Ethnic Study of Atherosclerosis participants. The MIP quality goal was 5 maneuvers, with the 2 largest values matching within 10 cm H2O. Correlates of MIP quality and values were assessed in logistic and linear regression models. RESULTS: The 3,849 participants with MIP measures were 51% female, 35% white, 26% African American, 23% Hispanic, and 16% Chinese American. Mean+/-SD MIP was 73+/-26 cm H2O for women and 97+/-29 cm H2O for men. The quality goal was achieved by 83% of the cohort and was associated with female sex, older age, race/ethnicity, study site, low ratio of forced expiratory volume in the first second to forced vital capacity (FEV1/FVC), and wheeze with dyspnea. The multivariate correlates of MIP were male sex, younger age, higher body mass index, shorter height, higher FVC, higher systolic blood pressure (in women) and health status (in men). There were no clinically important race/ethnic differences in MIP values. CONCLUSIONS: Race-specific reference equations for MIP are unnecessary in the United States. More than 80% of adults can be successfully coached for 5 maneuvers, with repeatability within 10 cm H2O.

Prevalence and associated factors of sarcopenia, dynapenia, and sarcodynapenia in community-dwelling elderly in São Paulo - SABE Study. / Prevalência e fatores associados à sarcopenia, dinapenia e sarcodinapenia em idosos residentes no Município de São Paulo - Estudo SABE.

OBJECTIVES: To estimate the prevalence of sarcopenia, dynapenia, and sarcodynapenia and associated factors in older adults in the city of São Paulo, Brazil. METHODS: A population-based, cross-sectional study was conducted with 1,168 older adults who participated in the third wave of the Health, Well-being, and Aging study in 2010 (SABE study). Men and women with skeletal muscle mass ≤ 8.90 and ≤ 6.37 kg/m2, respectively, were considered sarcopenic. Men and women with grip strength < 30 and < 20 kg, respectively, were considered dynapenic. Those with both conditions were considered sarcodynapenic. Sociodemographic, behavioral, clinical, nutritional, and biochemical characteristics were investigated as factors associated with each of the three conditions using multinomial logistic regression. RESULTS: Theprevalence of sarcopenia, dynapenia, and sarcodynapenia was 4.8% (95%CI 3.6 - 6.3), 30.9% (95%CI 27.5 - 34.6) and 9.0% (95%CI 7.2-11.3), respectively. An increase in age and malnutrition was associated with all the three conditions. Cognitive impairment was associated with both dynapenia and sarcodynapenia. Schooling, current smoking habit, and not having a marital life were associated with sarcopenia. Osteoarthritis, schooling, being an ex-smoker, and low hemoglobin were associated with dynapenia. Smoking habit and the risk of malnutrition were associated with sarcodynapenia. CONCLUSION: Dynapenia is more prevalent among older adults, followed by sarcodynapenia, and sarcopenia. With the exception of age, schooling, and malnutrition, the factors associated with sarcopenia and dynapenia are different. However, there are similarities in some associations regarding the presence of sarcodynapenia.

OBJETIVO: Estimar a prevalência e os fatores associados à sarcopenia, dinapenia e sarcodinapenia em idosos residentes no município de São Paulo. MÉTODOS: Estudo transversal de base populacional envolvendo 1.168 idosos pertencentes à terceira onda do Estudo SABE (Saúde, Bem-Estar e Envelhecimento), em 2010. Foramconsiderados sarcopênicos os idosos com índice de massa muscular esquelética ≤ 8,90 kg/m2 para homens e ≤6,37 kg/m2 para mulheres, dinapênicos aqueles com força de preensão manual < 30 kg para homens e < 20kg para mulheres, e sarcodinapênicos aqueles que apresentavam sarcopenia associada à dinapenia. Características sociodemográficas, comportamentais, condições clínicas, nutricionais e bioquímicas foram consideradas para determinar os fatores associados a cada uma das três condições por meio de regressão logística multinomial. RESULTADOS: A prevalência de sarcopenia, dinapenia e sarcodinapenia foi, respectivamente, 4,8% (IC95% 3,6-6,3), 30,9% (IC95% 27,5-34,6) e 9,0% (IC95% 7,2-11,3). O avanço da idade e a desnutrição foram associados às três condições analisadas. O prejuízo cognitivo foi associado à dinapenia e à sarcodinapenia. A escolaridade, ter o hábito de fumar e não ter vida conjugal foram associados à sarcopenia, enquanto osteoartrite, escolaridade, ser ex-fumante e apresentar valores baixos de hemoglobina foram associados à dinapenia. Foram associados à sarcodinapenia o hábito de fumar e o risco de desnutrição. CONCLUSÃO: Dinapenia é a condição mais prevalente na população idosa, seguida pela sarcodinapenia e sarcopenia. Exceto por idade, escolaridade e desnutrição, os fatores associados à sarcopenia e à dinapenia são distintos. Entretanto, há similaridades em algumas associações quando se trata da presença de sarcodinapenia.

Patterns and Correlates of Grip Strength in Older Americans.

BACKGROUND: Muscle strength is a sensitive indicator of morbidity and mortality in older adults. Loss of muscle strength contributes to a decline in physical functioning. Hand grip strength is a simple measurement but correlated with total body muscle strength. This study evaluated the patterns and correlates of grip strength among older adults in the United States. METHOD: The grip strength data were analyzed from the National Health and Nutrition Examination Survey. RESULT: Individuals (n=1009) aged ≥65 years old who had a grip strength measure were included in this analysis. Age distribution was 31.5%, 27.2%, 16.2%, and 25.0% for 65-69, 70-74, 75-79, and 80+ respectively. Race distribution was 81.1%, 8.3%, 7.1%, and 3.5% for Whites, Blacks, Hispanics, and Asians respectively. The mean grip strength was 71.7kg in males and 44.6kg in females, and declined as age increased (p<.0001). Blacks had the highest grip strength, followed by Whites and Hispanics, and Asians had the lowest measure (p<.0001). Although several variables were found to be correlated with grip strength univariately, after adjusting for gender, age, and race, the factors that remained significantly and independently associated with weak grip strength were lower body weight, not being in good health status, and physical limitations. CONCLUSION: Grip strength reduced as age increased. Blacks and Whites displayed higher grip strength than Asians and Hispanics. General health status, weight status and physical functioning were independently associated with grip strength. These findings suggest that grip strength could be a useful indicator for overall health assessment in older adults.

Clinical Features, Molecular Heterogeneity, and Prognostic Implications in YARS2-Related Mitochondrial Myopathy.

Importance: YARS2 mutations have been associated with a clinical triad of myopathy, lactic acidosis, and sideroblastic anemia in predominantly Middle Eastern populations. However, the identification of new patients expands the clinical and molecular spectrum of mitochondrial disorders. Objectives: To review the clinical, molecular, and genetic features of YARS2-related mitochondrial disease and to demonstrate a new Scottish founder variant. Design, Setting, and Participants: An observational case series study was conducted at a national diagnostic center for mitochondrial disease in Newcastle upon Tyne, England, and review of cases published in the literature. Six adults in a well-defined mitochondrial disease cohort and 11 additional cases described in the literature were identified with YARS2 variants between January 1, 2000, and January 31, 2015. Main Outcome and Measures: The spectrum of clinical features and disease progression in unreported and reported patients with pathogenic YARS2 variants. Results: Seventeen patients (median [interquartile range] age at onset, 1.5 [9.8] years) with YARS2-related mitochondrial myopathy were identified. Fifteen individuals (88%) exhibited an elevated blood lactate level accompanied by generalized myopathy; only 12 patients (71%) manifested with sideroblastic anemia. Hypertrophic cardiomyopathy (9 [53%]) and respiratory insufficiency (8 [47%]) were also prominent clinical features. Central nervous system involvement was rare. Muscle studies showed global cytochrome-c oxidase deficiency in all patients tested and severe, combined respiratory chain complex activity deficiencies. Microsatellite genotyping demonstrated a common founder effect shared between 3 Scottish patients with a p.Leu392Ser variant. Immunoblotting from fibroblasts and myoblasts of an affected Scottish patient showed normal YARS2 protein levels and mild respiratory chain complex defects. Yeast modeling of novel missense YARS2 variants closely correlated with the severity of clinical phenotypes. Conclusions and Relevance: The p.Leu392Ser variant is likely a newly identified founder YARS2 mutation. Testing for pathogenic YARS2 variants should be considered in patients presenting with mitochondrial myopathy, characterized by exercise intolerance and muscle weakness even in the absence of sideroblastic anemia irrespective of ethnicity. Regular surveillance and early treatment for cardiomyopathy and respiratory muscle weakness is advocated because early treatment may mitigate the significant morbidity and mortality associated with this genetic disorder.

Myosin storage (hyaline body) myopathy: a case report.

Myosin storage myopathy/hyaline body myopathy is a rare congenital myopathy, with less than 30 cases reported in the literature. It is characterised by the presence of subsarcolemmal hyaline bodies in type 1 muscle fibres and predominantly proximal muscle weakness. Recently, a single mutation (Arg1845Trp) in the slow/beta-cardiac myosin heavy chain gene (MYH7) was identified in four unrelated probands from Sweden and Belgium. The clinical severity and age of onset was variable, despite the same disease-causing mutation and similar histological findings. Here, we report the clinical and morphological findings of two brothers of English/Scottish background with the Arg1845Trp mutation in MYH7. This case report adds to the clinical description of this rare disorder and confirms that Arg1845Trp is a common mutation associated with this phenotype, at least in the White European population.

Phenotypic spectrum of disorders associated with glycyl-tRNA synthetase mutations.

We describe clinical, electrophysiological, histopathological and molecular features of a unique disease caused by mutations in the glycyl-tRNA synthetase (GARS) gene. Sixty patients from five multigenerational families have been evaluated. The disease is characterized by adolescent onset of weakness, and atrophy of thenar and first dorsal interosseus muscles progressing to involve foot and peroneal muscles in most but not all cases. Mild to moderate sensory deficits develop in a minority of patients. Neurophysiologically confirmed chronic denervation in distal muscles with reduced compound motor action potentials were features consistent with both motor neuronal and axonal pathology. Sural nerve biopsy showed mild to moderate selective loss of small- and medium-sized myelinated and small unmyelinated axons, although sensory nerve action potentials were not significantly decreased. Based on the presence or absence of sensory changes, the disease phenotype was initially defined as distal spinal muscular atrophy type V (dSMA-V) in three families, Charcot-Marie-Tooth disease type 2D (CMT2D) in a single family, and as either dSMA-V or CMT2D in patients of another large family. Linkage to chromosome 7p15 and the presence of disease-associated heterozygous GARS mutations have been identified in patients from each of the five studied families. We conclude that patients with GARS mutations present a clinical continuum of predominantly motor distal neuronopathy/axonopathy with mild to moderate sensory involvement that varies between the families and between members of the same family. Awareness of these overlapping clinical phenotypes associated with mutations in GARS will facilitate identification of this disorder in additional families and direct future research toward better understanding of its pathogenesis.

Prevalence of reduced muscle strength in older U.S. adults: United States, 2011-2012.

Five percent of adults aged 60 and over had weak muscle strength and 13% had intermediate muscle strength, as defined by the new FNIH criteria. Weak muscle strength is clinically relevant because it is associated with slow gait speed, an important mobility impairment. It is also linked to an increased risk of death. The prevalence of reduced muscle strength increased with age and was higher in non-Hispanic Asian and Hispanic persons than in non-Hispanic white or non-Hispanic black persons. Decreasing muscle strength was linked with increased difficulty in rising from an armless chair, which is another important type of mobility impairment.

Association of habitual dietary resveratrol exposure with the development of frailty in older age: the Invecchiare in Chianti study.

BACKGROUND: Resveratrol may play a protective role against the frailty syndrome (FS) because of its antioxidant and anti-inflammatory properties. OBJECTIVE: We prospectively evaluated the association between habitual dietary resveratrol exposure and the development of FS after 3-, 6-, and 9-y follow-up periods in a community-dwelling older population. DESIGN: We conducted a longitudinal analysis with the use of data from 769 participants aged ≥65 y from the Invecchiare in Chianti (Aging in Chianti) study. Total dietary resveratrol (TDR) intake was estimated at baseline with the use of a validated food-frequency questionnaire, which was developed to assess participants' usual food intakes over the previous year, and an ad hoc resveratrol database. Total urinary resveratrol (TUR) was analyzed with the use of liquid chromatography-tandem mass spectrometry with a previous solid-phase extraction at baseline. The combination of both measures [total dietary resveratrol plus total urinary resveratrol (TDR+TUR)] was computed with the use of the Howe's method. FS was assessed at baseline and at 3-, 6-, and 9-y of follow-up and was defined as the presence of ≥3 of the following 5 criteria: shrinking, exhaustion, sedentariness, slowness, and weakness. RESULTS: TDR+TUR concentrations were inversely associated with FS risk over 3-y of follow-up (OR for comparison of extreme tertiles: 0.11; 95% CI: 0.03, 0.45; P-trend = 0.002) but not after 6- and 9-y of follow-up in multinomial logistic regression models adjusted for baseline frailty status and potential confounders. These results did not differ when analyses were further adjusted for inflammatory markers. CONCLUSION: Higher habitual dietary resveratrol exposure was associated with lower risk of older community dwellers developing FS during the first 3 y of follow-up but not after longer follow-up periods.

Assessment of serum-mediated neurotoxicity in Navajo neuropathy.

Navajo neuropathy is a unique sensorimotor neuropathy which is geographically restricted to Navajo children living on the Navajo Reservation. Affected patients present with weakness, loss of sensation in extremities, corneal ulcerations, and a high incidence of childhood infections. Metabolic complications, such as severe liver disease, may further contribute to peripheral nerve injury in affected patients. In this study, serum-mediated injury to rat peripheral nerve was critically assessed. Serum samples from affected Navajo patients were tested in vivo for effects on peripheral nerve function. Injection of serum from affected Navajo patients into rat sciatic nerve produced a modest slowing of nerve conduction velocity without effecting evoked-compound muscle action potential (CMAP) amplitudes. By comparison, injection of serum from patients with MGUS neuropathy, an immune-mediated disorder, diminished evoked-CMAP amplitudes by approximately 70%. Navajo neuropathy sera had no effect in vitro on the neurite outgrowth of developing dorsal root ganglia neurons. The results argue against serum-mediated toxic injury to peripheral nerves in Navajo neuropathy.

Prevalência e fatores associados à sarcopenia, dinapenia e sarcodinapenia em idosos residentes no Município de São Paulo - Estudo SABE / Prevalence and associated factors of sarcopenia, dynapenia, and sarcodynapenia in community-dwelling elderly in São Paulo - SABE Study

RESUMO: Objetivo: Estimar a prevalência e os fatores associados à sarcopenia, dinapenia e sarcodinapenia em idosos residentes no município de São Paulo. Métodos: Estudo transversal de base populacional envolvendo 1.168 idosos pertencentes à terceira onda do Estudo SABE (Saúde, Bem-Estar e Envelhecimento), em 2010. Foramconsiderados sarcopênicos os idosos com índice de massa muscular esquelética ≤ 8,90 kg/m2 para homens e ≤6,37 kg/m2 para mulheres, dinapênicos aqueles com força de preensão manual < 30 kg para homens e < 20kg para mulheres, e sarcodinapênicos aqueles que apresentavam sarcopenia associada à dinapenia. Características sociodemográficas, comportamentais, condições clínicas, nutricionais e bioquímicas foram consideradas para determinar os fatores associados a cada uma das três condições por meio de regressão logística multinomial. Resultados: A prevalência de sarcopenia, dinapenia e sarcodinapenia foi, respectivamente, 4,8% (IC95% 3,6-6,3), 30,9% (IC95% 27,5-34,6) e 9,0% (IC95% 7,2-11,3). O avanço da idade e a desnutrição foram associados às três condições analisadas. O prejuízo cognitivo foi associado à dinapenia e à sarcodinapenia. A escolaridade, ter o hábito de fumar e não ter vida conjugal foram associados à sarcopenia, enquanto osteoartrite, escolaridade, ser ex-fumante e apresentar valores baixos de hemoglobina foram associados à dinapenia. Foram associados à sarcodinapenia o hábito de fumar e o risco de desnutrição. Conclusão: Dinapenia é a condição mais prevalente na população idosa, seguida pela sarcodinapenia e sarcopenia. Exceto por idade, escolaridade e desnutrição, os fatores associados à sarcopenia e à dinapenia são distintos. Entretanto, há similaridades em algumas associações quando se trata da presença de sarcodinapenia.

ABSTRACT: Objectives: To estimate the prevalence of sarcopenia, dynapenia, and sarcodynapenia and associated factors in older adults in the city of São Paulo, Brazil. Methods: A population-based, cross-sectional study was conducted with 1,168 older adults who participated in the third wave of the Health, Well-being, and Aging study in 2010 (SABE study). Men and women with skeletal muscle mass ≤ 8.90 and ≤ 6.37 kg/m2, respectively, were considered sarcopenic. Men and women with grip strength < 30 and < 20 kg, respectively, were considered dynapenic. Those with both conditions were considered sarcodynapenic. Sociodemographic, behavioral, clinical, nutritional, and biochemical characteristics were investigated as factors associated with each of the three conditions using multinomial logistic regression. Results: Theprevalence of sarcopenia, dynapenia, and sarcodynapenia was 4.8% (95%CI 3.6 - 6.3), 30.9% (95%CI 27.5 - 34.6) and 9.0% (95%CI 7.2-11.3), respectively. An increase in age and malnutrition was associated with all the three conditions. Cognitive impairment was associated with both dynapenia and sarcodynapenia. Schooling, current smoking habit, and not having a marital life were associated with sarcopenia. Osteoarthritis, schooling, being an ex-smoker, and low hemoglobin were associated with dynapenia. Smoking habit and the risk of malnutrition were associated with sarcodynapenia. Conclusion: Dynapenia is more prevalent among older adults, followed by sarcodynapenia, and sarcopenia. With the exception of age, schooling, and malnutrition, the factors associated with sarcopenia and dynapenia are different. However, there are similarities in some associations regarding the presence of sarcodynapenia.

Muscle strength, mass, and quality in older men and women with knee osteoarthritis.

OBJECTIVE: To examine the relationship between knee osteoarthritis (OA) and muscle parameters in a biracial cohort of older adults. METHODS: Participants in the Health, Aging and Body Composition Study (n = 858) were included in this cross-sectional analysis. Computed tomography was used to measure muscle area, and quadriceps strength was measured isokinetically. Muscle quality (specific torque) was defined as strength per unit of muscle area for both the entire thigh and quadriceps. Knee OA was assessed based on radiographic features and knee pain. We compared muscle parameters between those with and without radiographic knee OA (+RKOA group and -RKOA group, respectively) and among 4 groups defined by +RKOA and -RKOA with and without pain. RESULTS: The mean ± SD age was 73.5 ± 2.9 years and the mean ± SD body mass index (BMI) was 27.9 ± 4.8 kg/m(2) . Fifty-eight percent of participants were women and 44% were African American. Compared to the -RKOA participants, +RKOA participants had a higher BMI (30.2 versus 26.8 kg/m(2)), larger thigh muscles (117.9 versus 108.9 cm(2)), and a greater amount of intermuscular fat (12.5 versus 9.9 cm(2) ; all P < 0.0001). In adjusted models, the +RKOA participants had significantly lower specific torque (P < 0.001), indicating poorer muscle quality, than -RKOA participants, but there was no difference between groups in quadriceps specific torque. The +RKOA without pain (P < 0.05) and the +RKOA with pain (P < 0.001) participants had lower specific torque compared to the -RKOA without pain group. There were no significant differences in quadriceps specific torque among groups. CONCLUSION: Muscle quality was significantly poorer in participants with RKOA regardless of pain status. Future studies should address how lifestyle interventions might affect muscle quality and progression of knee OA.

Autosomal dominant late-onset quadriceps myopathy: three patients of a Taiwanese kindred.

OBJECTIVE: Primary quadriceps weakness/atrophy is a rare disorder with variable etiologies; therefore, this disorder has been regarded as a clinical syndrome rather than a distinct entity. However, three affected patients of a Taiwanese family demonstrate a uniform pattern of quadriceps weakness and atrophy, their clinical manifestations and pattern of inheritance may suggest a new disease entity. PATIENTS AND METHODS: Three patients in a Taiwanese kindred with selective quadriceps weakness and atrophy, which began after age 40 years, were examined. To disclose the confines of this disorder, muscle CT scans, electromyography, nerve conduction studies and muscle biopsies were performed; and to unravel and better understand the nature of this disorder, histopathological, ultrastructural, immunocytochemical and genetic studies were carried out. RESULTS: In two patients with long-standing disease, muscle imaging showed marked atrophy and fat replacement of the anterior thigh muscles and electromyography showed a mixture of myopathic and neuropathic changes. Muscle histopathology on the mildly affected tibialis anterior showed myopathic changes with myofibrillar degeneration and secondary neurogenic alterations. Immunocytochemical staining was not diagnostic but excluded the dystrophinopathies and other well-known muscular dystrophies. CONCLUSION: All previously identified diseases resulting in quadriceps weakness and atrophy have been ruled out and the present disorder appears to be a new disease entity of autosomal dominant late onset quadriceps myopathy.