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Table 1 Baseline characteristics in cases and controls, CPS II Nutrition Cohort Women (1999 to 2005)*

From: Serum 25-hydroxyvitamin D concentrations and postmenopausal breast cancer risk: a nested case control study in the Cancer Prevention Study-II Nutrition Cohort

Characteristic Cases (n = 516) Controls (n = 516) Pvalue‡‡
  Mean (SD)
Age at serum collection (year) 69.5 (5.9) 69.6 (5.8) 0.7
Plasma 25(OH)D (nmol/L) 56.5 (22.0) 56.2 (22.2) 0.8
Latitude (degree) 39.0 (4.7) 39.3 (4.8) 0.2
BMI at blood collection (kg/m2) 25.9 (4.9) 25.8 (4.8) 0.9
Weight gain since age 18 (kg) 14.1 (15.5) 11.1 (18.3) 0.006
Exercise METS† 15.4 (13.8) 15.6 (14.7) 0.9
Age at menarche (years) 12.7 (1.5) 12.7 (1.4) 0.6
Age at menopause (years) 48.6 (6.1) 47.8 (6.0) 0.03
  Percentage (%)
Family history of breast cancer 23.6 16.9 0.007
History of benign breast disease 33.9 27.5 0.01
Race    
   White 96.7 97.1 0.7
   Other (Black/Hispanic/Oriental) 3.3 2.9  
College graduate 24.2 23.4 0.5
Parity and age at first birth    
   Nulliparous 9.1 8.5 0.006
   <25, 1 to 2 live births 13.2 12.4  
   25+, 1 to 2 live births 22.5 14.7  
   <25, 3+ live births 35.3 45.0  
   25+, 3+ live births 20.0 19.4  
Postmenopausal hormone use    
   Never 22.1 25.4 0.4
   Former 58.1 53.1  
   Current 16.1 16.7  
Season of blood collection    
   Dec to Feb 15.1 18.2 0.1
   Mar to May 18.8 17.4  
   Jun to Aug 35.1 29.5  
   Sep to Nov 31.0 34.9  
Alcohol intake (≥ 1 drink/day) 21.3 16.1 0.1
Multivitamin use containing vitamin D‡    
   Not current user 30.8 34.9 0.6
   Current user 63.6 59.6  
Calcium supplement use    
   Not current user 32.4 32.9 0.5
   Current user 59.9 57.3  
Vitamin D supplement use§    
   Not current user 54.1 53.7 0.9
   Current user 16.1 16.9  
  Mean (SD)
Dietary variables #    
   Total calcium (mg/day) 1358.0 (565.2) 1293.7 (576.6) 0.08
   Dietary calcium (mg/day) 777.0 (285.3) 768.6 (283.0) 0.6
   Supplemental calcium (mg/day) 581.0 (504.3) 515.0 9493.4) 0.08
   Total vitamin D (IU/day) 439.5 (243.6) 415.0 (239.7) 0.1
   Dietary vitamin D (IU/day) 192.0 (105.3) 187.6 (96.1) 0.5
  1. * Standardized to age distribution of the study population.
  2. † Metabolic equivalent of task (METS) are defined for each type of exercise-related physical activity as a multiple of metabolic equivalent of sitting quietly for one hour.
  3. ‡ Reported on the 1999 questionnaire.
  4. § Reported at blood collection.
  5. # All dietary variables are adjusted for energy intake which was estimated from the 1992 brief Block Food Frequency Questionnaire (FFQ).
  6. ‡‡†† P values for categorical variables are based on the chi-squared test and P values for continuous variables are based on the t-test for difference of means.
  7. 25(OH)D = 25-hydroxyvitamin D; BMI = body mass index; CPS-II = Cancer Prevention Study-II; SD = standard deviation.
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