. 2022 Nov 23;77(3):342–347. doi: 10.1038/s41430-022-01241-z

Table 3.

Comparison of the changes in serum 25-hydroxyvitamin D levels between the experimental and control groups.

25-hydroxyvitamin D (ng/ml)	Experimental group (n = 64)	Control group (n = 72)	p value^a	p value^b
25-hydroxyvitamin D (ng/ml)	Mean ± SD	Mean ± SD	p value^a	p value^b
Baseline	21.15 ± 10.19	22.04 ± 10.42	0.618
Week 2	21.40 ± 9.85	20.97 ± 10.13
Δ	0.25 ± 3.10	−1.07 ± 2.68	0.009	0.018
p value^c	0.523	0.001
Week 4	21.90 ± 9.58	20.28 ± 10.07
Δ	0.75 ± 3.98	−1.75 ± 3.04	<0.001	<0.001
p-value^c	0.139	<0.001
Week 6	22.14 ± 9.53	20.33 ± 9.69
Δ	0.99 ± 4.97	−1.70 ± 3.64	0.001	0.002
p value^c	0.117	<0.001

Data are presented as mean ± standard deviation.

Δ represents a change from baseline.

SD standard deviation.

^aIndependent t-test was performed to examine between-group differences.

^bAnalysis of covariance adjusted for age, sex, time spent on outdoor activities, dietary vitamin D intake, compliance with device use, season of study enrollment, and baseline serum 25-hydroxyvitamin D levels, was performed to examine between-group differences.

^cPaired t-test was performed to examine within-group differences in changes from baseline serum vitamin D levels.