The relationship between serum vitamin D levels and sleep quality in fixed day indoor field workers in the electronics manufacturing industry in Korea

Table 5 Differences in the overall PSQI score and the scores for each item according to serum vitamin D level

Variables	Mean (SD)	Vitamin D				P value^a
		≥10 ng/mL		<10 ng/mL
		Mean (SD)		Mean (SD)
PSQI total score	3.97 2.26	3.85	2.15	4.25	2.37	0.002
Subjective sleep quality	0.99 0.61	0.96	0.61	1.05	0.63	0.020
Sleep latency	0.70 0.79	0.64	0.75	0.84	0.85	<0.001
Sleep duration	1.05 0.63	1.03	0.62	1.10	0.65	0.041
Habitual sleep efficiency	0.03 0.23	0.03	0.24	0.04	0.22	0.587
Sleep disturbances	0.63 0.50	0.62	0.49	0.64	0.51	0.613
Use of sleep medication	0.01 0.13	0.01	0.12	0.01	0.14	0.396
Daytime dysfunction	0.77 0.73	0.76	0.73	0.79	0.74	0.526

ISSN: 2052-4374