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Table 1 Selected characteristics of the population (N = 573)

From: Biomarkers of mammographic density in premenopausal women

Characteristics

Missing values (N)

Mean (SD) or N (%)

State of recruitment

0

 

Jalisco

 

318 (55.5)

Veracruz

 

255 (44.5)

Breast density (%)

0

36.5 (17.0)

Dense tissue area (cm2)

0

48.4 (33.3)

Non-dense area (cm2)

0

82.3 (38.5)

Age at mammography (years)

0

43.1 (3.7)

Age at menarche (years)

4

12.6 (1.5)

Family history of breast cancer (yes)

0

27 (4.7)

History of benign breast disease (yes)

0

79 (13.8)

Oral contraceptive use (ever)

19

288 (52.0)

Number of full-term pregnancies

30

2.1 (1.2)

Age at first birtha (years)

43

24.8 (4.4)

Duration of breastfeedinga

41

 

No breastfeeding

 

49 (10.4)

< 6 months

 

96 (20.4)

6 to 12 months

 

100 (21.3)

12 to 24 months

 

133 (28.3)

≥ 24 months

 

92 (19.6)

Physical activity (MET hours/week)

1

26.5 (21.1)

Alcohol intake (drinks/day)

45

 

0

 

160 (30.3)

< 0.1

 

259 (49.1)

0.1-0.2

 

76 (14.4)

≥ 0.2

 

33 (6.3)

Smoking status

62

 

Never

 

366 (71.6)

Past

 

87 (17.0)

Current

 

58 (11.4)

BMI (kg/m2)

0

28.4 (5.4)

< 25

 

168 (29.3)

25-30

 

214 (37.4)

≥30

 

191 (33.3)

Socioeconomic status

79

 

Low

 

84 (17.0)

Medium

 

216 (43.7)

High

 

194 (39.3)

  1. aAmong parous women (n = 511)
  2. Abbreviations: BMI body mass index; SD standard deviation