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Table 2 The light levels in the intervention group and the control group

From: Ambient bright light treatment improved proxy-rated sleep but not sleep measured by actigraphy in nursing home patients with dementia: a placebo-controlled randomised trial

  Mean (SD; min-max) vertical photopic lux Mean (SD; min-max) vertical melanopic lux Mean (SD; min-max) horizontal photopic lux Mean (SD; min-max) horizontal melanopic lux Mean (SD; min max) Kelvin vertical Mean (SD; min-max) Kelvin horizontal
Intervention 1039 (225; 722–1242) 915 (174; 676–1050) 1842 (528; 1388–2585) 1680 (557; 1270–2488) 5369 (251; 5088–5641) 5521 (275; 5211–5879)
Control 242 (102; 134–368) 137 (90; 56–261) 343 (65; 259–408) 178 (52; 106–218) 3049 (470; 2707–3622) 3048 (397; 2707–3048)
p-value .001 .000 .001 .002 .000 .000
  1. Note: Vertical lux was measured 120 cm above the floor in the middle of the room in four directions that were averaged to produce the mean vertical illumination. Mean horizontal lux was calculated as the mean of measurements 80 cm above the floor in the middle of the room and 50 cm from the back wall. Mean lux values were calculated for the intervention and control group by averaging the values across clusters. Differences between groups tested with Student’s t-test