Table 3.

Percentage of mammographic density and absolute density by selected characteristics of the rotating night shift work

Current rotating night shift work characteristicsnPercentage of density Adjusteda mean (95%CI)Absolute density, cm2 Adjusteda mean (95%CI)
Current night shift work frequency per month
 Day shifts (reference)31922.5 (20.8–24.3)21.8 (19.4–24.3)
 2–7 nights28523.6 (21.8–25.5)23.9 (21.2–26.5)
 8+ nights3623.7 (18.4–29.0)24.2 (16.7–31.7)
P0.400.27
Night shifts working hours,c h
 Day shifts (reference)31922.5 (20.7–24.2)21.8 (19.4–24.2)
 <108423.2 (19.9–26.5)22.7 (18.0–27.4)
 ≥10–1423023.8 (21.7–25.9)24.3 (21.3–27.3)
P0.340.20
Light at workc
 Day shifts (reference)31922.5 (20.7–24.2)21.8 (19.4–24.2)
 Dim13923.0 (20.4–25.6)23.0 (19.3–26.7)
 Full light14024.4 (21.8–27.1)25.1 (21.2–28.9)
 Surgical lamp3522.8 (17.7–28.0)22.8 (15.3–30.2)
Ptrend0.340.24
Activities at work during the night shiftc
 Day shifts (reference)31922.5 (20.7–24.2)21.8 (19.4–24.2)
 1b2326.8 (19.9–33.7)25.4 (15.9–35.0)
 1 and 2 or 222123.1 (21.1–25.2)23.3 (20.4–26.3)
 Any combination with 37024.1 (20.4–27.8)25.1 (19.6–30.6)
Ptrend0.430.24
  • aAdjustment for age, BMI, menopausal status, age at menopause, age at menarche, smoking, and season of the year.

  • bCategories of the activities: 1, taking care of patients, injections, administering pills; 2, small interventions; and 3, assistance in operations (deliveries).

  • cMissing information for 7 women.