Table 5.

Estimated aMT6s mesor (circadian mean) and acrophase (peak time) by light exposure among night shift workers (tertiles of mean light exposure from 24:00 to 05:00 hour and over the night shift)

MesorAcrophase
NCrude geometric mean (95% CI)aAdjusted mean % change (95% CI)bPcCrude geometric mean (95% CI)dAdjusted mean difference (95% CI)bPc
Day workers4115.4 (12.3–19.3)Ref.5:36 (5:06–6:12)Ref.
Night workers7210.9 (9.5–12.6)−33.8 (−48.4 to −15.1)<0.0018:42 (7:48–9:42)3.1 (1.8–4.4)<0.001
Mean light-at-night exposure from 24:00 to 05:00 hour (lux)
  ≤142411.4 (8.8–14.8)−30.3 (−49.9 to −3.1)0.0327:12 (5:36–9:00)1.7 (0.1–3.3)0.008
  15–402410.7 (8.4–13.5)−36.3 (−54.6 to −10.7)0.0099:18 (8:00–10:48)3.7 (1.8–5.6)<0.001
  41–3152410.7 (8.0–14.4)−35.0 (−53.0 to −10.0)0.0109:48 (7:48–12:06)3.7 (1.8–5.5)<0.001
Mean light-at-night exposure over the night shift (lux)
  <382411.3 (8.7–14.7)−27.3 (−47.8 to 1.3)0.0608:06 (6:18–10:24)2.5 (0.8–4.3)0.003
  38–552410.3 (8.2–13.0)−35.3 (−53.1 to −10.8)0.00810:18 (8:18–13:00)3.2 (1.4–5.0)<0.001
  55–2462411.2 (8.3–15.0)−37.7 (−55.1 to −13.6)0.0059:12 (7:18–11:30)3.2 (1.4–5.0)<0.001
  • aExpressed in ng/mg creatinine/hour.

  • bAdjusted for age, chronotype, educational level, sex, menopausal status, parity, and age at first full-term birth.

  • cWald test.

  • dExpressed as local time.