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Table 1 Characteristics of the study population (subjects with mammographic density data participating in the Generations Study)

From: Childhood body size and pubertal timing in relation to adult mammographic density phenotype

  Participants
Characteristic Adjusted mean percentage densitya Number Percentage of subjects
Age at mammogram, years
 47–54 25.5 303 27.4
 55–59 21.3 344 31.1
 60–64 18.0 279 25.2
 65–73 16.6 179 16.2
Interval between mammogram and baseline questionnaire
 ≥3 years prior 21.6 47 4.3
 2–2.9 years prior 24.3 61 5.5
 1–1.9 years prior 24.0 182 16.5
 Within 1 year 21.1 554 50.1
 1–1.9 years later 19.3 127 11.5
 2–2.9 years later 22.0 59 5.3
 ≥3 years later 17.2 75 6.8
BMI at baseline questionnaire, kg/m 2
 <20 33.0 39 3.5
 20–24 25.6 525 47.5
 25–29 15.7 378 34.2
 ≥30 12.1 163 14.8
Menopausal status at mammogram
 Postmenopausal 20.5 885 80.1
 Premenopausal 24.5 126 11.4
 Status not known 23.2 94 8.5
Parity
 Nulliparous 24.5 113 10.2
 Parous 20.9 992 89.8
   Age at first birth, years
   <25 19.9 428 38.7
   25–29 21.4 414 37.5
   ≥30 22.4 150 13.6
   Number of births    
   1 19.7 100 9.0
   2 21.1 583 52.8
   ≥3 21.0 309 28.0
Postmenopausal hormone replacement at time of mammogram  
 Never 21.0 839 75.9
 Former 21.0 199 18.0
 Current 25.7 67 6.1
Total study population 21.3 1105 100.0
  1. aMean percentage mammographic density (back-transformed to ordinary scale) for average body mass index (BMI) 25 kg/m2 and age 58 years at mammogram for all variables, except category of age at mammogram (at BMI 25 kg/m2 only) and category of BMI (at age 58 years only)