Skeletal muscle mass characteristics and elevated non‐communicable diseases in Saudi adults

The high burden of non‐communicable diseases in Saudi Arabia (SA), including obesity and hypertension, are partly explained by dramatic changes to both socioeconomic status and lifestyle. Low Skeletal muscle mass (SMM) is associated with cardiovascular risk factors including arterial stiffness, which may contribute to hypertension (1). The concurrence of obesity and low SM can also increase the risk of metabolic impairment and physical disability above either low SM or obesity alone(2). In absence of population‐specific cut‐offs, this study aimed to define reference levels for low SMM among SA men and women. This study is a secondary analysis of data obtained from several SA National Surveys (Saudi Health Information Survey 2013, National Health Survey 2004–2005, Capital‐wide Biomarker Screenings in Riyadh region 2008–2009 and 2013–2014, and the Riyadh Validation Survey 2013. Participants (18 years old and over) were randomly selected from the community. Blood pressure (BP), height, weight, waist and hip circumferences (WC, HC) were measured after informed consent. Blood samples were also collected in all surveys. Subjects with systolic BP ≥140 or Diastolic BP ≥90 mmHg, and/or diagnosed by physician with hypertension were considered as hypertensive. Subjects diagnosed by physician with diabetes mellitus type II and/or with HbA1c ≥6.1 mmol/L were considered as diabetics. Subjects with triglyceride >= 1.7 mmol/L, HDL cholesterol <1.04 mmol/L (♂) and <1.30 mmol/L (♀), total Cholesterol ≥6.2 mmol/L, and/or LDL Cholesterol≥4.9 mmol/L or diagnosed by physician were considered as dyslipidaemic. Whole‐body SMM was estimated with the Al‐Gindan equations (E1 & E2, validated among ethnic/racial groups using magnetic resonance imaging)(3). E1 SMM = 2.89 + 0.255   Body Weight ( kg ) ‐ 0.175   Hip   ( cm ) ‐ 0.038   Age   ( y ) + 0.118   Height   ( cm )E2 SMM = 39.5 + 0.665   Body Weight   ( kg ) ‐ 0.185   Waist   ( cm ) ‐ 0.418   Hip   ( cm ) ‐ 0.08   Age   ( y )The SMM (kg) output was divided by height (m) squared to generate Skeletal Muscle Mass Index (SMI) (muscle mass (kg)/height (m 2 )) (4). The SMI of all subjects were categorised in deciles. Prevalence of metabolic diseases in each decile was analysed using the Statistical Package for Social Sciences (SPSS) software, version 21.0 for Windows (SPSS Inc., Chicago, IL, USA). The Chi‐square test was performed to assess differences between the SMI deciles. The median age of participants with complete body composition data (n=15,028) was 39 (IQR 27–51). The median SM mass was 7.9 kg/m 2 (IQR7.3–8.6) in women and 9.9kg/m 2 (IQR 8.5–11.6) in men. The inter‐decile range is 2.6 kg/m 2 women and 6.4 kg/m 2 for men. The prevalence of metabolic diseases in each decile was significantly different (p< 0.05) among adult women and men for each risk category except any‐morbidity category in men (Table 1). Based on prevalence of metabolic diseases in each decile, it cannot be decided which decile would be a cut‐off for defining low SMM status among Saudi adults. Further normative data based on objective methods of body composition assessment such as MRI is needed to define reference levels of SMM for our population of interest.Risk Factors/Deciles Gender 1 2 3 4 5 6 7 8 9 10SMI ranges (kg/m 2 ) ♀(n=8498) 2–6.8 6.8–7.1 7.1–7.4 7.4–7.7 7.7–7.9 7.9–8.1 8.1–8.4 8.4–8.8 8.8–9.4 9.4–35.4♂(n=6530) 1.4–7.2 7.2–8.2 8.2–8.8 8.8–9.3 9.3–9.9 9.9–10.5 10.5–11.2 11.2–12 12–13.6 13.6–56.6BMI in each decile of SMI (median IQR) kg/m 2♀(n=7041) 26.6 (21.3–32) 23.5 (20.7–26.5) 25.5 (23.1–28.4) 27.1 (24.9–29.5 28.5 (26.3–30.9 30.4 (28.1–32.7) 32 (29.4–34.6) 33.6 (30.8–36.3) 35.9 (33.2–38.7) 39.3 (35.1–43.8)♂(n=5572) 25.9 (22.8–29.1) 24.8 (21.8–27.3) 25.4 (22–28.4) 26.4 (23.3–29.2) 27.1 (24.2–29.8) 27.8 (24.2–30.4) 28.7 (25.3–32) 30.1 (26.3–33.2) 31.3 (27.1–34.9) 33.3 (27.9–39.3)Any morbidity (n (%)) ♀(n=6007) * 563 (7.8) 547 (7.6) 579 (8.1) 598 (8.3) 588 (8.2) 624 (8.7) 620 (8.6) 620 (8.6) 629 (8.8) 639 (8.9)♂(n=4809) 478 (8.4) 487 (8.6) 480 (8.5) 483 (8.5) 481 (8.5) 463 (8.2) 485 (8.6) 472 (8.3) 482 (8.5) 498 (8.8)Any 2 co‐morbidities (n(%)) ♀(n=2575) * 231 (3.2) 187 (2.6) 200 (2.8) 248 (3.5) 242 (3.4) 285 (4) 276 (3.8) 288 (4) 298 (4.2) 320 (4.5)♂(n=2305) * 272 (4.8) 266 (4.7) 232 (4.1) 240 (4.2) 221 (3.9) 214 (3.8) 204 (3.6) 199 (3.5) 220 (3.9) 237 (4.2)Any 3 co‐morbidities (n(%)) ♀(n=727) * 66 (0.9) 60 (0.8) 48 (0.7) 66 (0.9) 64 (0.9) 77 (1.1) 79 (1.1) 76 (1.1) 90 (1.3) 101 (1.4)♂(n=650) * 80 (1.4) 79 (1.4) 61 (1.1) 58 (1) 61 (1.1) 63 (1.1) 60 (1.1) 46 (0.8) 74 (1.3) 68 (1.2)BMI: body mass index; SMI: skeletal muscle mass index; * Significantly different between deciles at p<0.05 (Chi square test).