REJUVENATION RESEARCH Volume 16, Number 6, 2013 ª Mary Ann Liebert, Inc. DOI: 10.1089/rej.2013.1442

Association of Androgen with Skeletal Muscle Mass and Muscle Function Among Men and Women Aged 50 Years and Older in Taiwan: Results from the I-Lan Longitudinal Aging Study An-Chun Hwang,1–3 Li-Kuo Liu,1,3 Wei-Ju Lee,1,4 Liang-Yu Chen,1–3 Ming-Hsien Lin,1,3 Li-Ning Peng,1–3 Chang Won Won,5 and Liang-Kung Chen1,3,5

Abstract

Purpose: The main aim of this study was to explore the association between skeletal muscle mass and muscle function by three different measures of bioactive testosterone, as well as dehydroepiandrosterone sulfate (DHEA-S) among men and women aged 50 years and older in Taiwan to facilitate further investigations of sarcopenia and androgen profile. Methods: The data of 532 participants (mean age 64.6 – 9.5 years; male, 53.0%) recruited from the I-Lan Longitudinal Aging Study was retrieved for analysis. Appendicular muscle mass, grip strength, and walking speed were stratified into quartiles in both genders to explore their associations with different hormones measures. Results: Among three different bioactive testosterone measures, the free androgen index had significant positive association with muscle mass ( p both < 0.001) and muscle strength in both genders ( p < 0.001 in men and p = 0.03 in women), whereas free testosterone and bioavailable testosterone displayed similar correlations only in the skeletal muscle mass of woman ( p both < 0.001) and muscle strength of men ( p = 0.007, p = 0.002, respectively). Serum levels of DHEA-S were correlated positively with skeletal muscle mass in men ( p = 0.013) and women aged 65 years and older ( p = 0.004) and handgrip strength in both genders ( p < 0.001 in men and p = 0.009 in women). None of the bioactive testosterone measurements was associated with walking speed, whereas DHEAS was significantly positively correlated with gait speed in both genders ( p both = 0.001). Conclusion: In conclusion, the free androgen index increased remarkably along with muscle mass and muscle strength among men and women aged 50 years and older. Moreover, DHEA-S was positively associated with muscle mass in men and older women and muscle strength in both sexes, and was also associated with aging and gait speed in both genders.

Introduction

S

arcopenia, defined as the progressive and generalized loss of skeletal muscle mass and muscle function (strength or performance),1 has been shown to be associated with various adverse outcomes, such as physical disability,2,3 poor quality of life, and even death.3–5 Age-related decline of skeletal muscle is a progressive process, which may be accelerated by decreased physical activities, insufficient nutritional intake, oxidative stress, chronic inflammation, and

hormonal changes.1,6,7 Although the complex interrelationship of these factors causing the decline of skeletal muscle still remains unclear, the decline of sex hormone, especially testosterone8–12 and dehydroepiandrosterone sulfate (DHEA-S)10,13,14 may play some role in its pathophysiology. In men, serum levels of total testosterone and bioactive testosterone may decrease 1%–2% per year after the age of 30.7 In women, although the level was much lower than men, it also dropped significantly from 20 to 45 years of age.7,15 Physiologically, testosterone may increase muscle synthesis,

1

Aging and Health Research Center, 2Institute of Public Health, National Yang Ming University, Taipei, Taiwan. Center for Geriatrics and Gerontology, Taipei Veterans General Hospital, Taipei, Taiwan. 4 Department of Family Medicine, Taipei Veterans General Hospital Yuanshan Branch, I-Lan, Taiwan. 5 Department of Family Medicine, Kyung Hee University School of Medicine, Seoul, South Korea. 3

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454 reduce muscle breakdown, facilitate the mesenchymal pluripotent cells into myogenic lineage, and promote the activities of motor neurons.16 On the other hand, DHEA-S, an adrenal steroid hormone, could be converted to active androgen by skeletal muscle and stimulates insulin-like growth factor-1(IGF-1), which is crucial to muscle growth and recovery.17 DHEA-S also acts as the main source of androgen in post-menopausal women. The serum level declines with age in both genders, and the levels in men aged 70 are only 10%–20% of younger counterparts.13,18,19 A number of studies exploring the relationship between aging, androgen, skeletal muscle mass, muscle strength, and physical performance have been done before.9,11,20 However, two main limitations exist in previous studies: (1) Women were rarely recruited for study, and (2) complete measurements of skeletal muscle mass, muscle strength, and physical performance for sarcopenia diagnosis were less commonly provided along with serum levels of sex hormones. In general, bioactive testosterone was considered more closely associated with clinical conditions than the levels of total testosterone. Several methods have been developed to measure bioactive testosterone, including free testosterone (free T), bioavailable testosterone (bioT), and free androgen index (FAI). Due to the difficulties of directly measuring free T, most studies used free T or bioT generated from previously developed equations instead.20–22 The most widely used equation was developed by Vermeulen et al., which had been validated in post-menopausal women and elderly men,23 but no study has been done to evaluate the association of these testosterone measurements with skeletal muscle mass, muscle strength, and physical function in both genders. Therefore, the main aim of this study is to explore the association between skeletal muscle mass and muscle function by three different measures of bioactive testosterone, i.e., FAI, bioT, and free T, as well as DHEA-S among men and women aged 50 years and older in Taiwan to facilitate further investigation of testosterone and sarcopenia. Materials and Methods Study population This study is part of the I-Lan Longitudinal Aging Study (ILAS), a population-based aging cohort study in the Yuanshan Township of I-Lan County, Taiwan. The ILAS was designed to explore the interrelationship between aging, frailty, sarcopenia, and cognitive decline in Asian populations. ILAS randomly selected community-dwelling people aged 50 years and older of Yuanshan Township of I-Lan County, Taiwan, by household registry. Selected residents were invited to participate by mail or phone calls and were enrolled when they had fully consented and agreed to participate. Subjects who met one of the following criteria were excluded from the study: (1) Inability of communication to complete the interview, (2) functionally dependent, i.e., unable to walk for 6 meters within a reasonable period of time, (3) limited life expectancy ( < 6 months) due to major illnesses, (4) currently institutionalized, or (5) contraindicated for magnetic resonance imaging. Data for this study were retrieved from the first wave of sampling. The entire study had been approved by the Institutional Review Board of Taipei Veterans General Hospital and National Yang Ming University.

HWANG ET AL. Anthropometry and measurements of sarcopenia Anthropometric measurements, including height, weight, and waist circumferences, for all participants were performed by research staff. Handgrip strength of the dominant hand was measured by dynamometers (‘‘Tokyo’’ TTM Original Smedlay¢s Dynamo Meter 100 kg) in a standing position. The best result from three measurements was recorded as the handgrip strength. A timed 6-meter walk was performed to evaluate the usual gait speed as the result of physical performance. All study subjects received the wholebody dual-energy X-ray absorptiometry (DXA) scan to measure lean body mass using a Lunar Prodigy instrument (GE Healthcare, Madison, WI). Appendicular skeletal muscle mass (ASM) was defined as the sum of the lean body mass of four limbs, and the skeletal muscle index was obtained by adjusting ASM by the square of the height measurement.24,25 Laboratory measurements All study subjects had 20 cc of whole blood sampled after a 10-hr overnight fast. Serum levels of total testosterone were measured using a chemiluminescense immunoassay analyzer (Siemens ADVIA Centaur). The intra-assay coefficient of variation (CV) and inter-assay CV were 5.8% and 4.7%, respectively. DHEA-S and sex hormone–binding globulin (SHBG) were measured by using electrochemiluminometry (Roche Elecsys e411). Analytical sensitivity and intra- and inter-assay CV were as follows: DHEA-S, 0.1 lg/dL, 4.02%, 2.4%; SHBG, 0.35 nmol/L, 2.57%, 2.7%, respectively. Free T and bioT were calculated from total testosterone, SHBG, and albumin by the Vermeulen method.23 Moreover, FAI was defined as total testosterone (nM/L)/SHBG (nM/L). Statistical analysis In this study, continuous variables were expressed as the mean – standard deviation, and categorical data were expressed as a percentage. All statistical analyses were performed by commercial statistical software (SPSS 18.0, Chicago,IL, USA). The Student t-test and analysis of variance (ANOVA) were used to compare continuous variables followed by post hoc analysis to compare values within each group. Results of skeletal muscle mass, handgrip strength, and gait speed were divided into quartiles to evaluate their associations with levels of hormones. A p value less than 0.05 (two-tailed) was considered statistically significant. Results During the study period, 532 participants (mean age, 64.6 – 9.5 years; male 53.0%) completed the study for analysis. Among them, 282 were men (age between 50 and 91 years; mean age, 65.9 – 10.1 years) and 250 were women (age between 50 and 87 years; mean age, 63.2 – 8.5 years). Table 1 summarizes demographic characteristics of the study subjects showing that women were significantly younger ( p = 0.001), with lower muscle mass and handgrip strength and slower gait speed (all p < 0.001), but body mass index (BMI) was similar to men ( p = 0.172). For hormone profiles, women had significantly lower testosterone-related measurements, SHBG, and DHEA-S (all p < 0.001). Table 2 summarizes the relationship between different sex hormone measurements and skeletal muscle mass. In men,

ANDROGEN, SKELETAL MUSCLE MASS, AND FUNCTION

455

Table 1. Demographic Characteristics of the Study Subjects of the I-Lan Longitudinal Aging Study Men (n = 281)

Women (n = 250)

p value

65.9 – 10.1 24.9 – 3.4 7.9 – 0.8 34.4 – 8.3 1.5 – 0.5 501.7 – 176.2 37.5 – 13.5 7.9 – 2.4 197.8 – 59.3 52.2 – 27.0 133.9 – 73.6

63.2 – 8.5 25.3 – 4.2 6.4 – 0.8 21.2 – 5.8 1.3 – 0.4 30.0 – 17.2 2.1 – 2.0 0.4 – 0.3 10.1 – 6.8 60.6 – 33.4 78.7 – 48.2

0.001 0.172 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001

Age (year) Body mass index (kg/m2) ASM/height2 (kg/m2) Grip strength (kg) Gait speed (meters/sec) Total testosterone (ng/dL) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) SHBG (nmol/L) DHEA-S (lg/dL)

ASM, appendicular skeletal muscle mass; SHBG, sex hormone–binding globulin; DHEA-S, dehydroepiandrosterone sulfate.

younger age, higher BMI, and FAI were significantly associated with higher skeletal muscle mass ( p all < 0.001), but not the other testosterone measurements. Meanwhile, serum levels of DHEA-S were positively correlated with skeletal muscle mass in men ( p = 0.013), but the main difference was on the lowest quartile in post hoc analysis. In women, age was not associated with skeletal muscle mass groups ( p = 0.898), but BMI was positively associated with skeletal muscle mass ( p < 0.001). All three bioactive testosterone measures were positively associated with skeletal muscle mass ( p < 0.001), and similar associations between DHEA-S and skeletal muscle mass were only seen among women aged 65 years and older ( p = 0.004). Associations of different sex hormone measures and handgrip strength are shown in Table 3. Overall, handgrip strength declined with age in both men and women ( p < 0.001) as well as lower BMI in men ( p = 0.003) but not women. In men, three bioactive testosterone measures all increased significantly along with handgrip strength ( p < 0.001,

p = 0.007, p = 0.002, respectively). However, in women, only FAI was positively associated with handgrip strength ( p = 0.032). In addition, DHEA-S was positively correlated with handgrip strength in both genders ( p < 0.001 in men and p = 0.009 in women). The associations of different sex hormone measures and gait speed showed that older people walked significantly slowly ( p < 0.001) (Table 4). However, none of the bioactive testosterone measurements was associated with walking speed, but DHEA-S was significantly positively correlated to gait speed in both genders ( p both = 0.001). The relationship between aging and hormone profiles is shown in Table 5. In men, FAI, free T, and bioT all declined with aging significantly ( p all < 0.001), whereas no remarkable change of testosterone measures was observed in post-menopausal women. SHBG levels were significantly increased with aging ( p < 0.001 in men and p = 0.017 in women), but DHEA-S levels decreased remarkably with aging in both genders ( p both < 0.001).

Table 2. Association of Skeletal Muscle Mass with Testosterone Measures and DHEA-S in Both Men and Women Skeletal muscle mass Men

Q1 (n = 63)

Q2 (n = 64)

Q3 (n = 64)

Q4 (n = 63)

p value

Age (year) Body mass index (kg/m2) ASM/height2 (kg/m2) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL)

71.3 – 10.1 22.0 – 2.5 6.9 – 0.4 32.6 – 10.6 7.7 – 2.2 184.8 – 55.7 108.3 – 67.5

66.4 – 10.0 24.1 – 2.3 7.6 – 0.2 35.1 – 14.2 7.6 – 2.5 181.9 – 60.2 143.9 – 83.9

64.9 – 9.4 25.6 – 2.5 8.1 – 0.1 39.9 – 12.1 8.3 – 2.3 199.4 – 58.3 138.6 – 68.6

61.4 – 8.4 27.7 – 3.3 8.9 – 0.4 42.5 – 14.6 8.1 – 2.3 198.1 – 56.9 146.2 – 71.7

< 0.001 < 0.001 < 0.001 < 0.001 0.332 0.204 0.013

Women

Q1 (n = 61)

Q2 (n = 57)

Q3 (n = 58)

Q4 (n = 58)

p value

Age Body mass index (kg/m2) ASM/height2 (kg/m2) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL) 50–64 years S65 years

62.3 – 8.8 22.1 – 2.8 5.5 – 0.4 1.3 – 1.1 0.28 – 0.17 6.9 – 4.2 69.3 – 40.2 73.5 – 36.9 47.9 – 31.2

63.2 – 8.5 24.5 – 2.9 6.1 – 0.1 2.1 – 1.9 0.42 – 0.28 10.2 – 6.8 86.2 – 62.2 104.9 – 64.7 48.7 – 34.0

63.2 – 7.6 26.0 – 3.3 6.5 – 0.1 2.5 – 2.6 0.47 – 0.33 11.7 – 8.2 89.6 – 45.6 90.0 – 40.0 88.4 – 51.7

63.3 – 7.8 28.2 – 3.7 7.3 – 0.6 2.8 – 2.0 0.50 – 0.29 12.2 – 6.8 74.8 – 42.6 87.9 – 47.5 66.7 – 38.9

0.898 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 0.077 0.052 0.004

ASM, appendicular skeletal muscle mass; DHEA-S, dehydroepiandrosterone sulfate.

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HWANG ET AL. Table 3. Association of Muscle Strength with Testosterone Measures and DHEA-S in Both Men and Women Handgrip strength

Men

Q1 (n = 77)

Q2 (n = 65)

Q3 (n = 81)

Q4 (n = 59)

p value

Age (year) Body mass index (kg/m2) Handgrip strength (kg) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL)

73.6 – 10.3 24.0 – 3.5 24.3 – 4.4 32.0 – 12.1 7.2 – 2.3 173.5 – 56.6 106.4 – 70.8

68.3 – 8.5 24.7 – 3.3 31.8 – 1.6 35.7 – 13.3 7.8 – 2.7 187.2 – 67.0 122.7 – 60.4

62.7 – 7.9 25.0 – 3.3 38.1 – 2.1 39.7 – 13.8 8.3 – 2.3 199.7 – 56.5 155.3 – 78.1

57.7 – 4.7 26.1 – 3.2 45.5 – 3.5 43.6 – 12.0 8.5 – 2.1 209.9 – 51.1 152.7 – 71.5

< 0.001 0.003 < 0.001 < 0.001 0.007 0.002 < 0.001

Women

Q1 (n = 69)

Q2 (n = 59)

Q3 (n = 71)

Q4 (n = 50)

p value

Age Body mass index (kg/m2) Handgrip strength (kg) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL)

68.0 – 9.5 24.6 – 4.8 14.4 – 3.6 1.8 – 1.8 0.40 – 0.33 9.5 – 7.7 61.9 – 40.8

63.9 – 7.8 25.5 – 4.2 20.0 – 0.7 1.8 – 1.6 0.38 – 0.23 9.3 – 5.8 83.3 – 56.9

60.5 – 7.0 25.5 – 3.3 23.3 – 1.3 2.4 – 2.5 0.43 – 0.28 10.6 – 6.9 83.4 – 44.8

59.4 – 6.5 25.9 – 4.2 29.1 – 3.2 2.7 – 2.0 0.45 – 0.26 11.1 – 6.6 88.5 – 46.6

< 0.001 0.336 < 0.001 0.032 0.574 0.479 0.009

DHEA-S, dehydroepiandrosterone sulfate.

Discussion Overall, results of this study showed that skeletal muscle mass, muscle strength, and gait speed declined along with aging in both genders. However, aging was not significantly associated with decline of skeletal muscle mass in women, which was different from previous studies from Western countries.26,27 Men with greater skeletal muscle mass and muscle strength were associated with higher BMI; however, BMI was positively associated with skeletal muscle mass but not muscle strength in women. As for different measures of bioactive testosterone, FAI was positively related to muscle mass and muscle strength in both genders, but free T and bioT displayed similar correlations only in skeletal muscle

mass of woman and muscle strength of men. A previous study showed that free T was more closely associated with BMI than age in postmenopausal women, which was compatible with our study.28 DHEA-S was the sex hormone measure that positively correlated with gait speed in our analysis, suggesting that DHEA-S may be a suitable hormonal indicator for physical performance. The relationship between androgen, muscle mass, and physical performance in older people had been reported, but rarely has this association been explored in women. Although serum levels of bioactive testosterone in older women were much lower than men, the associations between testosterone, skeletal muscle mass, muscle strength, and physical performance in older women were similar to men.

Table 4. Association of Gait Speed with Testosterone Measures and DHEA-S in Both Men and Women Gait speed Men

Q1 (n = 82)

Q2 (n = 62)

Q3 (n = 76)

Q4 (n = 62)

p value

Age (year) Body mass index (kg/m2) Gait speed (meters/sec) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL)

71.2 – 10.3 24.7 – 3.4 1.0 – 0.2 35.3 – 12.7 7.7 – 2.3 182.4 – 56.1 108.5 – 56.0

68.1 – 10.0 25.1 – 3.6 1.3 – 0.1 37.0 – 15.0 8.1 – 2.8 195.1 – 70.5 141.0 – 79.4

63.4 – 8.8 24.7 – 3.2 1.6 – 0.1 38.0 – 13.6 8.0 – 2.3 195.8 – 59.0 136.8 – 72.8

59.7 – 7.5 25.0 – 3.5 2.1 – 0.3 40.1 – 12.8 8.0 – 2.0 195.9 – 51.1 156.9 – 80.8

< 0.001 0.855 < 0.001 0.198 0.736 0.410 0.001

Women

Q1 (n = 71)

Q2 (n = 77)

Q3 (n = 64)

Q4 (n = 37)

p value

Age Body mass index (kg/m2) Gait speed (meters/sec) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL)

68.5 – 9.5 25.6 – 4.8 0.9 – 0.1 1.9 – 1.9 0.39 – 0.26 9.4 – 6.3 62.6 – 43.2

63.5 – 7.5 25.2 – 4.0 1.2 – 0.1 2.4 – 2.3 0.45 – 0.28 10.9 – 6.6 75.0 – 40.9

60.1 – 6.6 26.0 – 4.1 1.5 – 0.1 2.0 – 1.6 0.38 – 0.24 9.3 – 5.9 94.3 – 60.0

57.5 – 4.8 23.8 – 3.2 2.0 – 0.3 2.2 – 2.4 0.44 – 0.38 11.0 – 9.4 88.9 – 39.0

< 0.001 0.085 < 0.001 0.412 0.344 0.363 0.001

DHEA-S, dehydroepiandrosterone sulfate.

ANDROGEN, SKELETAL MUSCLE MASS, AND FUNCTION

457

Table 5. Association of Age and Sex Hormone in Both Men and Women Age group Men Age (year) Body mass index (kg/m2) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL) SHBG (nmol/L) Women Age Body mass index (kg/m2) Free androgen index Free testosterone (ng/dL) Bioavailable testosterone (ng/dL) DHEA-S (lg/dL) SHBG (nmol/L)

50–64 years (n = 149)

65–74 years (n = 71)

75 years and older (n = 62)

p value

57.8 – 4.1 25.4 – 3.5 42.5 – 13.8 8.4 – 2.4 206.8 – 59.2 161.6 – 77.6 44.6 – 27.4

70.0 – 2.8 24.7 – 3.2 35.2 – 11.6 7.9 – 2.3 190.9 – 54.8 114.5 – 55.7 57.6 – 24.1

80.1 – 4.3 23.9 – 3.2 28.2 – 8.5 6.6 – 2.1 156.8 – 49.7 89.6 – 49.7 64.2 – 23.6

< 0.001 0.015 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001

50–64 years (n = 71)

65–74 years (n = 77)

75 years and older (n = 64)

p value

57.6 – 3.7 25.2 – 4.0 2.3 – 2.2 0.42 – 0.30 10.4 – 7.1 88.8 – 49.0 57.2 – 32.0

69.9 – 2.7 25.8 – 3.8 2.1 – 1.9 0.42 – 0.28 10.1 – 6.6 65.2 – 41.9 62.8 – 32.9

79.7 – 3.3 24.9 – 5.7 1.4 – 1.3 0.35 – 0.21 8.3 – 5.2 53.0 – 39.8 76.8 – 39.3

< 0.001 0.528 0.095 0.513 0.444 < 0.001 0.017

DHEA-S, dehydroepiandrosterone sulfate; SHBG, sex hormone–binding globulin.

Van et al. have reported that higher free T and FAI were significantly associated with lean body mass and maximal quadriceps extensor strength in post-menopausal women, which was basically compatible with our findings.12 FAI has been widely used as the measurement of bioactive testosterone in women,29 although the validity in men was less consistent. Ly et al. have proposed that the free androgen index correlated with bioactive testosterone poorly in men, and the deviation became much smaller with low total serum testosterone and high SHBG.30 Our study demonstrated that FAI acts as a better indicator than other bioavailable testosterone measurements in terms of relationship between testosterone and muscle mass/ muscle strength in older people. More importantly, the association can be clearly shown in both genders. Many studies have investigated the effect of administrating testosterone or DHEA in treating sarcopenia for the elderly. Although results of randomized controlled trials evaluating the effect of DHEA supplementation were inconsistent, Nair et al. clearly reported no beneficial effect of DHEA supplement on body composition or physical performance in both genders.31 However, the benefits of DHEA supplementation may become more significant when exercise or weight training was incorporated.32,33 Maggio et al. have reviewed the effect of testosterone; the treatment was associated with increased muscle mass in older men, whereas the effects on muscle strength and physical function were less clear.10 Nevertheless, the benefit on muscle strength and physical performance was mostly seen in the frail population.11,34 The strength of our study is that we collected comprehensive data in both genders, including precise muscle mass measurement by DXA, muscle strength, physical performance, and different sex hormone measures. The results of the study proved that bioactive testosterone, i.e., FAI, was closely associated with muscle mass and muscle function in both genders. There were several limitations in this study. First, the participants of our study were younger than previous studies, and the decline of sex hormone and quantity and quality of skeletal muscle may be less remarkable. Sec-

ond, the cohort recruited relatively healthier people from the communities, so the results may overestimate the skeletal muscle quantity and quality than the real communitydwelling older people. However, decline of sex hormone, skeletal muscle mass, and muscle function is a progressive and continuing phenomenon that eventually occurs earlier in life, so the results of this study are of great importance for following research in sarcopenia. Third, the lack of real free T measurements in this study failed to examine its relationship between three adjusted measurements of bioactive testosterone. However, it is a common condition in the literature. In conclusion, the FAI increased remarkably along with muscle mass and muscle strength among men and women aged 50 years and older, and it could be a simple but useful marker clinically. Moreover, DHEA was positively associated with muscle mass in men and older women and muscle strength in both sexes, and was the sex hormone associated with aging and gait speed in both genders as well. Further investigation is needed to explore the physiologic interaction of sex hormones and decline of muscle mass and muscle function. Acknowledgments We express our gratitude to the staff in Center for Geriatrics and Gerontology of Taipei Veterans General Hospital and Department of Family Medicine of Taipei Veterans General Hospital Yuanshan Branch, and to all the participants for their assistance. This work was supported by R1201001 awarded by Taipei Veterans General Hospital. Author Disclosure Statement The authors declared no conflict of interest. References 1. Cruz-Jentoft AJ, Baeyens JP, Bauer JM, Boirie Y, Cederholm T, Landi F, Martin FC, Michel JP, Rolland Y, Schneider SM,

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459 Address correspondence to: Liang-Kung Chen Center for Geriatrics and Gerontology Taipei Veterans General Hospital No. 201, Section 2, Shih-Pai Road Taipe, 11217 Taiwan E-mail: [email protected] Received: April 29, 2013 Accepted: August 4, 2013

Association of androgen with skeletal muscle mass and muscle function among men and women aged 50 years and older in Taiwan: results from the I-Lan longitudinal aging study.

The main aim of this study was to explore the association between skeletal muscle mass and muscle function by three different measures of bioactive te...
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