Table 2.

Association between light and urinary melatonin

ModelRegression coefficientP
Light exposure
Full population
Peak urinary melatonina−0.033010.49
Change in urinary melatoninb−0.031280.58
Night shift only
Peak urinary melatoninc−0.040370.07
Change in urinary melatonind−0.054940.04
Day shift only
Peak urinary melatonine−0.083710.47
Change in urinary melatoninf0.043920.75
Premenopausal women only
Peak urinary melatoning0.045350.50
Change in urinary melatoninh−0.076480.27
  • aAdjusted for use of antidepressant medication and the number of caffeinated beverages consumed during the 24 hours of melatonin assessment.

  • bAdjusted for use of antidepressants, oral contraceptives, and the numbers of caffeinated beverages consumed during the 24 hours of melatonin assessment.

  • cAdjusted for total number of years of shift work and use of antidepressant medication.

  • dAdjusted for use of antidepressant medication.

  • eAdjusted for menopausal status and the number of caffeinated beverages consumed during the 24 hours of melatonin collection.

  • fAdjusted for menopausal status, antidepressant and migraine medication use, the number of caffeinated beverages consumed during the 24 hours of melatonin assessment and total number of years of shift work.

  • gAdjusted for total number of years of shift work, number of days since previous menstrual period, smoking, and both number of alcoholic beverages and number of caffeinated beverages consumed during the 24 hours of melatonin assessment. Four overly influential individuals removed to improve model fit.

  • hNo variables changed the parameter estimate by more than 10%, therefore no confounders included in model.