Table 2.

Differences in overall PSQI score and scores for each item according to vitamin D level

Variable	Mean (95% CI)	Vitamin D
		Sufficiency Mean (95% CI)	Deficiency Mean (95% CI)	P value *
PSQI total score	6.33 (6.03–6.62)	6.19 (5.90–6.47)	7.02 (6.18–7.86)	0.039
Subjective sleep quality	1.04 (0.97–1.10)	1.00 (0.93–1.07)	1.20 (1.08–1.32)	0.004
Sleep latency	1.48 (1.39–1.57)	1.50 (1.39–1.61)	1.43 (1.27–1.59)	0.458
Sleep duration	0.80 (0.70–0.89)	0.76 (0.67–0.85)	1.00 (0.69–1.32)	0.022
Sleep efficiency	0.72 (0.64–0.80)	0.71 (0.62–0.79)	0.79 (0.55–1.03)	0.517
Sleep disturbances	1.35 (1.30–1.41)	1.33 (1.27–1.39)	1.45 (1.31–1.59)	0.105
Use of sleep medication	0.31 (0.24–0.38)	0.27 (0.20–0.35)	0.42 (0.27–0.57)	0.086
Daytime dysfunction	0.62 (0.56–0.69)	0.61 (0.54–0.69)	0.72 (0.55–0.89)	0.177

PSQI, Pittsburgh Sleep Quality Index.

Vitamin D concentrations were classified according to the Institute of Medicine as deficient when 25(OH)D < 20 ng/mL and sufficient when 25(OH)D ≥ 20 ng/mL.

^⁎Comparisons made using the Student t test.