Table 1.

Background of subjects

		Dark condition (n=17)	Well-lit condition (n=10)
Sex	Male	0	1
	Female	17	9
Age	Mean±SD	34.6±13.2	36.0±13.1
Mean duration of work	Mean±SD	12.4±13.6	13.6±13.4
Sleep disorder	No	11	7
	No answer	6	3
Sleeping drug	No	12	7
	No answer	5	3
Past illness	Allergy	1	0
	Asthma	1	1
	Myoma of the uterus	1	0
	Fatty liver	0	1
	Slipped disk	1	0
Corrected eyesight	Left	0.94±0.27	0.76±0.43
	Right	0.92±0.32	0.81±0.63