Table 1.

Baseline characteristics of women by breast cancer status, Guernsey IV study, United Kingdom

Cases (n = 111), median (range)*Noncases (n = 3,100), median (range)*
Demographic characteristics
Age at entry (yrs)53.2 (40.3-79.9)51.8 (34.1-79.8)
Age at exit (yrs)63.4 (44.2-85.2)66.9 (42.9-93.7)
Age left full-time education (yrs)15 (11-19)15 (11-20)
Occupation: manager/supervisor6.3%8.2%
Social class I-II34.2%31.2%
Reproductive characteristics
Age at menarche (yrs)§13 (10-17)13 (9-18)
Nulliparity18.9%12.4%
Age at first birth (yrs)(among parous women only)24 (18-39)24 (16-42)
Parity (among parous women only)2 (0-5)2 (0-12)
Still premenopausal at entry36.9%36.8%
Age at natural menopause (yrs)49 (39-58)50 (36-60)
Ever use of OC50.9%50.8%
On OC at GIV1.8%1.1%
Ever use of HRT21.6%26.7%
On HRT at GIV5.4%6.9%
Anthropometric characteristics at GIII
Height (m)161 (147-176)160 (120-200)
BMI23.9 (19.1-33.3)24.3 (16.0-58.7)
Weight gain from GIII to GIV**25.5%18.4%
Weight loss from GIII to GIV**5.5%9.4%
Mammographic features
Qualitative (Wolfe grade)
    N115.3%34.4%
    P119.8%20.6%
    P253.2%35.8%
    DY11.7%9.3%
Quantitative
Percent breast density (%)33.7 (2.9-67.4)31.5 (0.28-80.5)
Total area of dense tissue (cm2)33.0 (2.8-143.5)30.0 (0.39-169.9)
Total area of lucent tissue (cm2)72.2 (19.10-253.3)70.7 (6.4-334.9)
Total area of the breast (cm2)105.0 (35.4-271.4)105.9 (19.2-339.4)
Total volume of the breast (cm3)704.7 (184.2-2133.4)717.4 (79.3-3416.6)
Fractal dimension††2.45 (2.37-2.53)2.45 (2.34-2.62)
Regional skewness††0.54 (0.07-2.09)0.47 (−0.23 to 5.54)
Lacunarity††4.98 (4.44-5.43)4.99 (4.16-5.51)
  • NOTE: Abbreviations: BMI, body mass index; GIII/IV, Guernsey III/IV; HRT, hormone replacement therapy; OC, oral contraceptives.

  • * Cases include 94 invasive and 17 in situ tumors; median (range) for quantitative variables and percentage for qualitative variables.

  • Values missing for 64 women.

  • Values missing for two women.

  • § Values missing for 14 women.

  • Value missing for one woman.

  • Values missing for 72 women.

  • ** Values missing for nine women.

  • †† These measures have no units.