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Table 2 Multivariable-adjusted geometric mean concentrations of urinary aMT6s (ng/mg creatinine) at urine collection (1996–1999) by categories of body size and night shift work among 1,343 women in Nurses’ Health Study II a

From: The association of body size in early to mid-life with adult urinary 6-sulfatoxymelatonin levels among night shift health care workers

    Model 1b   Model 2c  
Variable Category definition N Geometric Mean (95% CI) P-trend Geometric Mean (95% CI) P-trend
Birth weight (pounds)d <5.5 34 35 (29–43)   34 (28–42)  
  5.5-6.9 299 43 (40–46)   42 (39–45)  
  7.0-8.4 632 41 (40–44)   42 (40–44)  
  8.5-9.9 137 44 (40–49)   45 (40–50)  
  ≥10 19 31 (24–41) 0.88 32 (24–42) 0.46
Somatotype at age 5 1 (leanest) 307 43 (40–46)   42 (39–45)  
  2 417 41 (39–44)   41 (38–43)  
  3 354 43 (40–46)   43 (41–46)  
  4 161 40 (37–44)   42 (38–46)  
  ≥5 (heaviest) 86 41 (36–47) 0.47 44 (38–50) 0.50
Somatotype at age 10 1 (leanest) 254 41 (38–45)   40 (37–43)  
  2 426 43 (41–46)   42 (40–45)  
  3 326 42 (39–45)   42 (40–45)  
  4 193 41 (38–45)   42 (39–46)  
  ≥5 (heaviest) 132 40 (36–45) 0.49 43 (39–48) 0.24
Height (inches) ≤62 236 42 (38–45)   42 (39–45)  
  63-64 391 43 (40–46)   43 (40–46)  
  65 193 43 (40–47)   43 (39–47)  
  66-67 316 40 (37–43)   40 (38–43)  
  ≥68 207 41 (37–44) 0.30 41 (37–44) 0.23
Body mass index at age 18 (kg/m2) <19 306 45 (42–48)   42 (39–46)  
  19-19.9 260 41 (38–44)   40 (37–43)  
  20-22.4 516 43 (41–46)   44 (41–46)  
  22.5-24.9 160 35 (32–39)   38 (34–42)  
  25-27.4 59 36 (31–42)   41 (34–48)  
  ≥27.5 32 39 (31–49) 0.001 45 (36–56) 0.86
Weight change since age 18 (kg) <5 452 45 (43–48)   41 (39–44)  
  5- < 20 633 42 (40–44)   42 (40–44)  
  ≥20 229 36 (33–39) <0.0001 43 (38–48) 0.66
Waist circumference (inches) <26.75 163 45 (41–50)   41 (37–46)  
  26.75 - < 29 203 49 (45–54)   46 (42–51)  
  29- < 31 183 41 (37–45)   40 (36–44)  
  31- < 34.5 182 38 (34–41)   40 (36–44)  
  ≥34.5 117 36 (32–40) <0.0001 43 (37–50) 0.49
Waist to hip ratio <0.72 150 46 (41–51)   44 (40–49)  
  0.72- < 0.75 162 44 (40–49)   42 (38–47)  
  0.75- < 0.79 220 42 (38–45)   41 (38–45)  
  0.79- < 0.82 154 38 (35–43)   40 (36–44)  
  ≥0.82 158 40 (36–45) 0.02 43 (39–48) 0.55
Body mass index at urine collection (kg/m2) <20 137 50 (45–56)    
  20-22.4 366 46 (43–49)    
  22.5-24.9 340 43 (40–46)    
  25-27.4 209 38 (35–42)    
  27.5-29.9 105 37 (33–41)    
  ≥30 162 34 (30–37) <0.0001   
Shift work 2 weeks prior to urine collection (nights) 0 1227 42 (41–44)    
  1-4 76 40 (35–46)    
  >4 37 38 (31–47) 0.29   
Shift work 2 years prior to urine collection (months) 0 1158 42 (41–44)    
  1-9 78 43 (37–49)    
  10-19 26 38 (30–49)    
  ≥20 73 37 (32–43) 0.08   
Cumulative shift work prior to urine collection (years)e 0 447 43 (40–45)    
  1-9 804 41 (40–43)    
  ≥10 85 42 (36–48) 0.37   
  1. aaMT6s, 6-sulfatoxymelatonin.
  2. bAnalyses of body size adjusted for age at urine collection (5 year age categories), first-morning urine (yes, no), batch, number of pack-years smoked (0, <10, 10–24, ≥25 pack years), parity (nulliparous, 1–2 children, ≥3 children), physical activity in MET-hours/week (quintiles), and night shift work in 2 weeks prior to urine collection (0, 1–4 , >4 night shifts). Multivariable analyses for shift work adjust for the same factors except they adjust for body mass index (BMI) in kg/m2 at urine collection (<20, 20.0-22.4, 22.5-24.9, 25.0-27.4, 27.5-29.9, ≥30) instead of night shift work in 2 weeks prior to urine collection.
  3. cAnalyses of body size adjust for the same factors as model 1, plus BMI in kg/m2 at urine collection (<20, 20.0-22.4, 22.5-24.9, 25.0-27.4, 27.5-29.9, ≥30).
  4. dAmong women (n = 1,185) who were born full-term.
  5. eCumulative shift work, updating baseline lifetime shift work history through urine collection.