Table 3.

Kendall tau and Spearman correlation coefficient (95% CI) for correlation between corneal illuminance approximated from H-LEA questionnaire and photopic illuminance and circadian irradiance from Daysimeter measurements (criterion standard)a

Kendall τCrude Spearman correlation raAdjusted Spearman correlation ra
Photopic illuminance
 Overall (n = 132)0.570.720.72
 Day workers (n = 47)0.630.770.77
 Night workers (n = 85)0.540.680.68
 Day 10.570.710.71
 Day 20.610.760.76
 Day 30.590.740.74
 Day 40.550.690.70
 Day 50.550.690.69
 Day 60.540.680.69
 Day 70.590.730.73
Circadian light
 Overall (n = 132)0.580.720.73
 Day workers (n = 47)0.630.780.78
 Night workers (n = 85)0.550.690.69
 Day 10.570.720.72
 Day 20.610.760.77
 Day 30.590.740.74
 Day 40.560.700.70
 Day 50.550.700.70
 Day 60.550.690.69
 Day 70.590.740.74
  • aAll correlation and Kendall τ coefficients are statistically significant (P < 0.0001). Crude values are adjusted for nurses' ID only; adjusted values are adjusted for nurses' ID, age, BMI, day of the 7-day collection, and whether or not they were current night workers.