Clinical Endocrinology (2015) 82, 509–516
doi: 10.1111/cen.12509
ORIGINAL ARTICLE
Decreased muscle mass is not an independent risk factor for metabolic syndrome in Korean population aged 70 or older Hyung Suk Koo*, Moon Jong Kim*, Kwang-Min Kim† and Young-Sang Kim* *Department of Family medicine, CHA University, CHA Bundang Medical Centre, Seongnam and †Department of Family medicine Ajou University, School of Medicine, Suwon, Korea
Introduction Summary Context The association of low muscle mass with cardiometabolic risks is still controversial. Objective The aim of this study was to investigate the relationship between low muscle mass and metabolic syndrome (MetS) according to the various muscle mass indices and to evaluate the influence of muscle mass on MetS independent of fat mass. Design Cross-sectional study Subjects About 841 men and 1106 women aged 70 or older from Korea National Health and Nutrition Examination Survey 2008–2010 Measurements We used various muscle mass indices: appendicular skeletal muscle mass (ASM) divided by height squared (ASM/Ht2), ASM divided by body weight (ASM/Wt) and ASM adjusted for height and fat mass (residual). Low muscle mass is defined as ASM/Ht2 and ASM/Wt below 2 SD of the sex-specific mean for healthy young adults. The sex-specific lowest quintile of the distribution of the residual was regarded as low muscle mass. Results The prevalence of MetS was higher in the population with low muscle mass defined by ASM/Wt, but lower in those defined by ASM/Ht2. However, after stratification according to the central obesity, low muscle mass was barely related with MetS. Meanwhile, when both ASM and fat mass were included in a logistic regression model, the odds ratios of 1 SD change of ASM for MetS were 107 (085–134) for men and 124 (104– 147) for women, respectively. Conclusions The relationship between low muscle mass and MetS was different according to the various muscle mass indices. After controlling the influence of fat mass, decreased muscle mass was not an independent risk factor for MetS. (Received 14 March 2014; returned for revision 4 April 2014; finally revised 9 May 2014; accepted 19 May 2014)
An age-related decline in muscle mass and function is termed sarcopenia.1 Comparing with young adults, a 30% reduction in muscle mass is noted in the elderly aged 80.2 Various factors such as genetic heritability, nutritional status, physical activity, hormones, pro-inflammatory cytokines and so forth are considered as potential causes of muscle mass loss.1 Muscle mass loss is not only correlated with functional decline and disability,3,4 but also associated with increased mortality.5 Visceral fat mass is an important factor for metabolic syndrome (MetS) and strongly associated with cardiometabolic risks.6 However, the function of muscle mass on MetS has not well been established. Since skeletal muscles play a role in whole-body glucose metabolism and insulin sensitivity,7 low muscle mass (LMM) in addition to high fat mass may be a predisposing factor for cardiometabolic risks. While the indices such as body mass index (BMI), waist circumference (WC) and fat proportion were widely used to define obesity and adiposity, the methods for defining muscle mass and function were recently introduced.8 Skeletal muscle mass measurements are usually adjusted for height, weight or fat mass;3,4,9 muscle strength and gait speed are used as surrogate markers for the muscle function.1,8 These indices are used for defining LMM or sarcopenia. Epidemiological studies investigating the relationship between sarcopenia and cardiometabolic factors yielded conflicting results. In some cross-sectional studies, LMM, defined by weight-adjusted method, was related with cardiometabolic risks;10–12 other studies were inconclusive for such findings.13–15 Based upon Korea National Health and Nutrition Examination Survey (KNHANES), we investigated the differences in the relationship between MetS and LMM according to the defining methods. In addition, we evaluated whether MetS is influenced by muscle mass independent of fat mass.
Methods Correspondence: Young-Sang Kim, Department of Family medicine, CHA University, CHA Bundang Medical Centre, 463-712 59 Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, Korea. Tel.:+82 31 780 5360; Fax:+82 31 780 5944; E-mail: [email protected] © 2014 John Wiley & Sons Ltd
Study subjects This study was based on the data acquired from the second and third years (2008–2009) of KNHANES IV and the first 509
510 H. S. Koo et al. year (2010) of KNHANES V. KNHANES, a survey to assess the health and nutritional status of the noninstitutionalized civilian populations of Korea since 1998, is a cross-sectional and nationally representative survey conducted by the Division of Chronic Disease Surveillance, Korea Centres for Disease Control and Prevention. The overall survey consisted of surveys for health-related interviews, nutritional statuses and health examinations. Data were collected via household interviews and by direct standardized physical examinations conducted in medically equipped mobile examination centres. This survey included 3583, 7920 and 7043 participants in 2008–2010, respectively. Since the potential causes of sarcopenia may accumulate with ageing1 and the prevalence of LMM started to elevate from 70s in Korean population,16 we analysed the population aged 70 years or older. We excluded the subjects who were not amenable for the body composition by dualenergy X-ray absorptiometry (DXA) or the components of MetS. Finally, 841 men and 1106 women were included for the analysis (Fig. 1). All the participants in this survey signed an informed consent form. Medical history and lifestyle habits Medical history information and lifestyle habits were collected using self-reported questionnaires. Smoking history was categorized into the three groups: current smoker, ex-smoker and nonsmoker. Drinking was classified into rarely (
doi: 10.1111/cen.12509
ORIGINAL ARTICLE
Decreased muscle mass is not an independent risk factor for metabolic syndrome in Korean population aged 70 or older Hyung Suk Koo*, Moon Jong Kim*, Kwang-Min Kim† and Young-Sang Kim* *Department of Family medicine, CHA University, CHA Bundang Medical Centre, Seongnam and †Department of Family medicine Ajou University, School of Medicine, Suwon, Korea
Introduction Summary Context The association of low muscle mass with cardiometabolic risks is still controversial. Objective The aim of this study was to investigate the relationship between low muscle mass and metabolic syndrome (MetS) according to the various muscle mass indices and to evaluate the influence of muscle mass on MetS independent of fat mass. Design Cross-sectional study Subjects About 841 men and 1106 women aged 70 or older from Korea National Health and Nutrition Examination Survey 2008–2010 Measurements We used various muscle mass indices: appendicular skeletal muscle mass (ASM) divided by height squared (ASM/Ht2), ASM divided by body weight (ASM/Wt) and ASM adjusted for height and fat mass (residual). Low muscle mass is defined as ASM/Ht2 and ASM/Wt below 2 SD of the sex-specific mean for healthy young adults. The sex-specific lowest quintile of the distribution of the residual was regarded as low muscle mass. Results The prevalence of MetS was higher in the population with low muscle mass defined by ASM/Wt, but lower in those defined by ASM/Ht2. However, after stratification according to the central obesity, low muscle mass was barely related with MetS. Meanwhile, when both ASM and fat mass were included in a logistic regression model, the odds ratios of 1 SD change of ASM for MetS were 107 (085–134) for men and 124 (104– 147) for women, respectively. Conclusions The relationship between low muscle mass and MetS was different according to the various muscle mass indices. After controlling the influence of fat mass, decreased muscle mass was not an independent risk factor for MetS. (Received 14 March 2014; returned for revision 4 April 2014; finally revised 9 May 2014; accepted 19 May 2014)
An age-related decline in muscle mass and function is termed sarcopenia.1 Comparing with young adults, a 30% reduction in muscle mass is noted in the elderly aged 80.2 Various factors such as genetic heritability, nutritional status, physical activity, hormones, pro-inflammatory cytokines and so forth are considered as potential causes of muscle mass loss.1 Muscle mass loss is not only correlated with functional decline and disability,3,4 but also associated with increased mortality.5 Visceral fat mass is an important factor for metabolic syndrome (MetS) and strongly associated with cardiometabolic risks.6 However, the function of muscle mass on MetS has not well been established. Since skeletal muscles play a role in whole-body glucose metabolism and insulin sensitivity,7 low muscle mass (LMM) in addition to high fat mass may be a predisposing factor for cardiometabolic risks. While the indices such as body mass index (BMI), waist circumference (WC) and fat proportion were widely used to define obesity and adiposity, the methods for defining muscle mass and function were recently introduced.8 Skeletal muscle mass measurements are usually adjusted for height, weight or fat mass;3,4,9 muscle strength and gait speed are used as surrogate markers for the muscle function.1,8 These indices are used for defining LMM or sarcopenia. Epidemiological studies investigating the relationship between sarcopenia and cardiometabolic factors yielded conflicting results. In some cross-sectional studies, LMM, defined by weight-adjusted method, was related with cardiometabolic risks;10–12 other studies were inconclusive for such findings.13–15 Based upon Korea National Health and Nutrition Examination Survey (KNHANES), we investigated the differences in the relationship between MetS and LMM according to the defining methods. In addition, we evaluated whether MetS is influenced by muscle mass independent of fat mass.
Methods Correspondence: Young-Sang Kim, Department of Family medicine, CHA University, CHA Bundang Medical Centre, 463-712 59 Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, Korea. Tel.:+82 31 780 5360; Fax:+82 31 780 5944; E-mail: [email protected] © 2014 John Wiley & Sons Ltd
Study subjects This study was based on the data acquired from the second and third years (2008–2009) of KNHANES IV and the first 509
510 H. S. Koo et al. year (2010) of KNHANES V. KNHANES, a survey to assess the health and nutritional status of the noninstitutionalized civilian populations of Korea since 1998, is a cross-sectional and nationally representative survey conducted by the Division of Chronic Disease Surveillance, Korea Centres for Disease Control and Prevention. The overall survey consisted of surveys for health-related interviews, nutritional statuses and health examinations. Data were collected via household interviews and by direct standardized physical examinations conducted in medically equipped mobile examination centres. This survey included 3583, 7920 and 7043 participants in 2008–2010, respectively. Since the potential causes of sarcopenia may accumulate with ageing1 and the prevalence of LMM started to elevate from 70s in Korean population,16 we analysed the population aged 70 years or older. We excluded the subjects who were not amenable for the body composition by dualenergy X-ray absorptiometry (DXA) or the components of MetS. Finally, 841 men and 1106 women were included for the analysis (Fig. 1). All the participants in this survey signed an informed consent form. Medical history and lifestyle habits Medical history information and lifestyle habits were collected using self-reported questionnaires. Smoking history was categorized into the three groups: current smoker, ex-smoker and nonsmoker. Drinking was classified into rarely (
