Table 3. Adjusted geometric means of prolactin concentration by selected characteristics of
rotating night shift work
Premenopausal women Postmenopausal women Night shift work characteristics N Adjusted* prolactin
(µIU/ml) Geometric mean (95%CI) N Adjusted* prolactin (µIU/ml) Geometric mean (95%CI)
Current rotating night shift work No Yes p 170 218 236.7 (217.2-257.9) 227.3 (211.3-244.6) 0.542 160 109 151.4 (140.9-162.7) 147.3 (134.5-161.2) 0.663
Total duration of night shift work (years) -5 >5 - ≤15 >15 - ≤ 25 >25 p-trend 40 89 179 80 215.0 (185.2-249.7) 255.6 (231.1-282.7) 226.0 (211.0-242.1) 226.5 (203.7-251.7) 0.140 38 72 63 96 158.2 (137.6-181.8) 150.8 (136.4-166.8) 142.5 (128.2-158.5) 150.5 (137.5-164.6) 0.688
Total number of hours of night shift work by tertiles# 1st (<13056 h) 2nd (13056 – 24304 h) 3rd (>24304 h) p-trend 120 159 109 243.5 (222.1-267.0) 227.5 (211.6-244.7) 224.1 (204.5-245.6) 0.446 97 61 111 153.9 (141.0-168.1) 148.4 (133.2-165.3) 146.8 (135.1-159.6) 0.745
Total number of night shifts <1000 1000-1999 ≥ 2000 p-trend 108 166 114 248.1 (225.5-273.0) 229.2 (213.5-246.1) 219.6 (200.9-240.0) 0.216 79 69 121 159.9 (145.0-176.3) 149.4 (135.0-165.3) 143.6 (132.7-155.5) 0.271
*adjusted for: time of blood sampling (hour), cigarette smoking within 24 h before blood sampling (Yes/No), calendar season when blood sample was collected (July-September/October-June), parity with breastfeeding(nulliparous, parous who breastfed, parous who never breastfeed); in addition among postmenopausal women age and age at menopause
