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Table 1 Comparison of characteristics of women participating in the California Teachers Study mammographic density substudy who were included in the analyses with those of participants who were excluded from the analyses

From: Hormone metabolism pathway genes and mammographic density change after quitting estrogen and progestin combined hormone therapy in the California Teachers Study

Characteristics Interviewed participants not included in the current analysis (n = 720) Interviewed participants included in the current analysis (non-Hispanic white EPT quitters) (n = 284) P values
At cohort enrollment    
Age (mean ± SD) 49.9 ± 4.2 (range 40-60) 50.5 ± 3.8 (range 41-60) 0.07
BMI (kg/m2) 24.6 ± 4.8 (range 17-50) 24.7 ± 4.9 (range 17-47) 0.68
White (N (%)) 624 (87%) 284 (100%)  
Nulliparous women (N (%)) 141 (20%) 63 (22%) 0.33
Menopausal status    
 Premenopausal 432 (60%) 155 (55%) 0.012
 Perimenopausal 87 (12%) 55 (19%)  
 Postmenopausal 201 (28%) 74 (26%)  
Ever had breast biopsy (N (%)) 108 (15%) 40 (14%) 0.71
Positive 1st degree family history of breast cancer (N (%)) 64 (9%) 37 (13%) 0.053
At mammogram substudy enrollment    
Age at interview (mean ± SD) 62 ± 4.0 (range 52-71) 62 ± 3.6 (range 53-72) 0.11
BMI (kg/m2) 26.2 ± 5.2 (range 17-49) 25.7 ± 5.0 (range 18-47) 0.16
Positive 1st degree family history of breast cancer (N (%)) 112 (16%) 51 (18%) 0.43
Number of mammograms in the past 10 years 8.8 ± 2.3 (range 2-20) 8.9 ± 2.2 (range 2-18) 0.59
At time of mammography evaluated for density    
Age at time of mammogram while taking EPT   56 ± 4 (range 45-67)  
Age at time of mammogram while off EPT   60 ± 5 (range 49-71)  
BMI at time of mammogram while taking EPT   25.7 ± 5.2 (range 18-47)  
BMI at time of mammogram while off EPT   25.8 ± 5.0 (range 18-48)  
Years on EPT at time of mammogram while taking EPT    
 <1 year   15 (5%)  
 1- < 4 years   121 (43%)  
 4- < 7 years   112 (39%)  
 ≥7 years   36 (13%)  
Time interval between two mammograms (years)    
 ≤3 years   141 (50%)  
 4-5 years   106 (37%)  
 6-9 years   37 (13%)  
  1. EPT, estrogen and progestin combined therapy; BMI, body mass index.