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Table 2 Main results comparing the effect of melatonin with placebo on the components of the metabolic syndrome*

From: Melatonin supplementation to treat the metabolic syndrome: a randomized controlled trial

Parameter Melatonin Placebo P value (mixed model)
Weight, kg (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 97.6 ± 16.9 96.2 ± 15.7  
  Post 95.8 ± 15.9 96.8 ± 15.7  
  Change with treatment (post minus pre) -1.4 ± 4.4 -0.02 ± 1.8 0.087
BMI (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 34.6 ± 6.7 33.8 ± 6.0  
  Post 33.7 ± 6.1 34.0 ± 6.0  
  Change with treatment (post minus pre) -0.4 ± 1.4 -0.0 ± 0.7 0.090
Waist circumference, cm (mean, SD)    
  Sample size (pre, post) (n = 37, 37) (n = 38, 37)  
  Pre 108.8 ± 12.2 106.8 ± 10.5  
  Post 108.1 ± 11.3 108.0 ± 10.6  
  Change with treatment (post minus pre) (n = 35 Melatonin) -0.9 ± 5.9 1.0 ± 5.5 0.155
Triglycerides, mg/dL (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 207.2 ± 271.9 175.3 ± 172.1  
  Post 142.6 ± 74.1 172.4 ± 216.9  
  Change with treatment (post minus pre) -66.3 ± 211.8 -4.2 ± 99.6 0.166
LDL cholesterol, mg/dL (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 112.6 ± 32.3 112.7 ± 31.2  
  Post 108.5 ± 33.2 114.6 ± 35.3  
  Change with treatment (post minus pre) -3.7 ± 25.6 0.1 ± 25.5 0.564
HDL cholesterol, mg/dL (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 40.8 ± 7.6 42.5 ± 10.1  
  Post 40.9 ± 8.3 41.5 ± 8.3  
  Change with treatment (post minus pre) -0.2 ± 5.8 -1.1 ± 8.2 0.592
Fasting glucose, mg/dL (mean, SD)    
  Sample size (pre, post) (n = 39, 37) (n = 38, 37)  
  Pre 103.4 ± 16.5 104.6 ± 13.7  
  Post 102.9 ± 17.1 101.9 ± 10.2  
  Change with treatment (post minus pre) 0.3 ± 13.6 -3.1 ± 11.0 0.287
SBP average clinic value, mmHg (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 126.8 ± 16.3 122.3 ± 17.3  
  Post 123.4 ± 15.2 127.0 ± 15.1  
  Change with treatment (post minus pre) -2.7 ± 11.3 4.7 ± 13.8 0.013
DBP average clinic value, mmHg (mean, SD)    
  Sample size (pre, post) (n = 39, 38) (n = 38, 37)  
  Pre 76.6 ± 11.3 75.3 ± 10.3  
  Post 75.0 ± 10.8 76.4 ± 10.0  
  Change with treatment (post minus pre) -1.1 ± 6.9 1.1 ± 7.4 0.243
Ambulatory BP readings    
Full 24-hour period    
  Average SBP, mmHg (mean, SD)    
  Sample size (pre, post) (n = 37, 38) (n = 38, 37)  
  Pre 131.6 ± 11.6 130.4 ± 9.5  
  Post 129.6 ± 12.0 130.9 ± 12.0  
  Change with treatment (post minus pre) (n = 36 Melatonin) -1.4 ± 8.1 0.3 ± 8.5 0.475
  Average DBP, mmHg (mean, SD)    
  Sample size (pre, post) (n = 37, 38) (n = 38, 37)  
  Pre 76.9 ± 9.0 76.3 ± 8.2  
  Post 75.7 ± 8.6 76.8 ± 8.3  
  Change with treatment (post minus pre) (n = 36 Melatonin) -1.0 ± 6.3 0.4 ± 5.7 0.409
Wake period (0800 to 2200)    
  Average SBP, mmHg (mean, SD)    
  Sample size (pre, post) (n = 37, 38) (n = 38, 37)  
  Pre 136.1 ± 12.4 134.2 ± 9.3  
  Post 133.2 ± 12.2 135.8 ± 12.6  
  Change with treatment (post minus pre) (n = 36 Melatonin) -2.2 ± 9.1 1.4 ± 10.5 0.169
  Average DBP, mmHg (mean, SD)    
  Sample size (pre, post) (n = 37, 38) (n = 38, 37)  
  Pre 81.0 ± 9.6 79.8 ± 8.0  
  Post 78.9 ± 9.1 81.6 ± 8.7  
  Change with treatment (post minus pre) (n = 36 Melatonin) -1.8 ± 7.3 1.8 ± 6.6 0.044
Sleep period (2200 to 0800)    
  Average SBP, mmHg (mean, SD)    
  Sample size (pre, post) (n = 37, 36) (n = 38, 37)  
  Pre 125.8 ± 12.3 125.1 ± 11.5  
  Post 124.9 ± 13.4 123.9 ± 13.5  
  Change with treatment (post minus pre) (n = 34 Melatonin) -1.1 ± 9.0 -1.4 ± 8.9 0.807
  Average DBP, mmHg (mean, SD)    
  Sample size (pre, post) (n = 37, 36) (n = 38, 37)  
  Pre 71.7 ± 9.1 71.2 ± 9.5  
  Post 70.7 ± 8.8 69.9 ± 8.7  
  Change with treatment (post minus pre) (n = 34 Melatonin) -0.7 ± 6.5 -1.3 ± 6.7 0.729
  1. *The mean values in the “Change with treatment (post minus pre)” rows may not equal exactly the difference between the above corresponding “pre” and “post” rows because of different sample sizes due to subject drop out in the post- versus the pre-period.
  2. DBP = diastolic blood pressure; SBP = systolic blood pressure; SD = standard deviation.