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Table 1 Descriptive characteristics of the participant groups

From: Blood and skeletal muscle ageing determined by epigenetic clocks and their associations with physical activity and functioning

  Young adults Middle-aged Older adults
  FTC, N = 93 ERMA, N = 47 FTC, N = 46
  Mean (SD) Mean (SD) Mean (SD)
Socio-economic and life style factors    
Age, year 32.9 (5.3) 51.8 (2.0) 63.7 (4.2)
Age, range 23–42 48–55 57–69
Sex, male/female, n 62/47 –/47 18/28
Education, n (%)+    
 Primary 1 (1.0) 2 (4.3) 9 (20.5)
 Secondary 52 (51.5) 26 (55.3) 26 (59.1)
 Tertiary 48 (47.5) 19 (40.4) 9 (20.5)
Smoking, n (%)    
 Never 43 (46.2) 31 (66.0) 26 (56.5)
 Former 27 (29.1) 13 (27.7) 14 (30.4)
 Current 23 (24.7) 3 (6.4) 6 (13.0)
Alcohol, drinks per week¤ 4.4 (7.4) 4.2 (4.5) 3.1 (5.5)
Body composition#    
Body mass index, kg/m2 28.7 (5.8) 26.0 (3.6) 28.9 (5.7)
Fat mass, kg 30.4 (13.7) 26.0 (8.2) 30.9 (9.9)
Lean body mass, kg 51.4 (10.8) 42.6 (4.5) 46.1 (9.1)
Percentage of fat, % 34.9 (10.1) 35.8 (7.0) 38.5 (8.1)
Physical activity    
Sport index 2.8 (0.99)   2.1 (1.1)
Leisure index 2.9 (0.60)   2.7 (0.80)
Work index 2.8 (0.82)   3.0 (0.51)
Self-reported physical activity, n (%)    
 Low   6 (12.8)  
 Medium   13 (27.7)  
 High   28 (59.6)  
Monitored physical activity    
 MVPA, min   56.1 (32.2)  
 Step counts per day   9 337 (3 378)  
Physical function phenotypes    
VO2max, ml/kg/min* 35.2 (8.5)   
Maximal workload, W 195.8 (54.7)   
Walking test, 6 min distance (m)   670 (65)  
Hand grip strength (N)   331 (56)  
Knee extension torque (Nm)   486 (95)  
Vertical jumping height (m)   0.19 (0.043)  
  1. +missing data in education variable N = 10, ¤one drink = 12 g/100% alcohol; #Body composition is estimated by dual-energy X-ray absorptiometry; *N = 60; MVPA moderate to vigorous physical activity, VO2max maximal oxygen uptake