Table 2. Multivariate-adjusted^a mean serum 25-hydroxyvitamin D concentration (ng/ml) in relation to demographic and lifestyle factors according to survey season and sex.

	Workplace A (July)						Workplace B (November)
	Men (n = 100)			Women (n = 61)			Men (n = 212)			Women (n = 156)
	n	Mean (SE)	P valueb	n	Mean (SE)	P valueb	n	Mean (SE)	P valueb	n	Mean (SE)	P valueb
Age (years)
<35	22	28.4 (1.6)		18	23.7 (2.3)		52	22.9 (1.1)		55	16.9 (1.8)
35–44	38	28.1 (1.3)	0.83	30	25.2 (2.1)	0.26	75	23.8 (0.9)	0.49	52	19.7 (1.7)	0.02
≥45	40	28.9 (1.2)	0.73	13	25.9 (2.5)	0.31	85	22.3 (1.0)	0.62	49	19.7 (1.7)	0.04
	P for interaction = 0.45						P for interaction = 0.07
Body mass index (kg/m2)
<21	14	27.2 (1.8)		38	26.9 (2.2)		52	22.9 (1.1)		84	18.3 (1.6)
21–22.9	27	28.6 (1.4)	0.42	14	28.0 (2.5)	0.43	58	23.0 (1.1)	0.90	31	18.2 (1.8)	0.97
23–24.9	20	29.9 (1.4)	0.14	2	22.6 (3.8)	0.23	41	24.3 (1.2)	0.31	21	19.1 (1.9)	0.59
≥25	39	28.2 (1.3)	0.54	7	22.3 (2.1)	0.04	61	21.9 (1.1)	0.46	20	19.6 (2.1)	0.40
	P for interaction = 0.25						P for interaction = 0.17
Occupation
Office work	93	27.5 (0.7)		34	24.5 (2.2)		185	22.8 (0.6)		111	18.7 (1.6)
Others	7	29.5 (2.0)	0.32	27	25.3 (2.1)	0.51	27	23.2 (1.3)	0.78	45	18.8 (1.7)	0.96
	P for interaction = 0.32						P for interaction = 0.89
Smoking
Nonsmoker	57	29.2 (1.2)		59	24.4 (1.2)		118	24.6 (0.9)		152	19.3 (0.8)
Current smoker	43	27.8 (1.3)	0.20	2	25.5 (3.5)	0.74	94	21.4 (0.9)	0.002	4	18.2 (3.0)	0.74
	P for interaction = 0.89						P for interaction = 0.64
Alcohol drinking
Nondrinker	16	26.6 (1.6)		18	25.5 (2.0)		28	22.1 (1.4)		54	18.5 (1.8)
<20 g/day	52	29.6 (1.2)	0.046	40	25.9 (1.9)	0.77	111	22.0 (0.9)	0.98	90	19.5 (1.7)	0.35
≥20 g/day	32	29.3 (1.4)	0.12	3	23.3 (3.4)	0.48	73	25.0 (1.0)	0.07	12	18.3 (2.1)	0.92
	P for interaction = 0.55						P for interaction = 0.20
Non-job physical activity
None	34	29.0 (1.4)		33	24.0 (2.1)		77	20.9 (0.9)		78	19.2 (1.6)
<2 hours/week	20	29.5 (1.5)	0.76	17	25.0 (2.3)	0.46	46	23.6 (1.2)	0.04	41	19.0 (1.7)	0.86
≥2 hours/week	46	27.0 (1.3)	0.11	11	25.8 (2.5)	0.39	89	24.5 (1.0)	0.002	37	18.0 (1.9)	0.32
	P for interaction = 0.10						P for interaction = 0.004
Vitamin D intake (µg/1000 kcal)
T1 (<4.54)	36	29.8 (1.3)		16	23.7 (2.3)		73	20.9 (1.0)		51	17.2 (1.7)
T2 (4.54–<7.0)	34	27.5 (1.4)	0.07	27	24.7 (2.3)	0.49	64	23.5 (1.0)	0.03	52	19.3 (1.7)	0.08
T3 (≥7.0)	30	28.3 (1.4)	0.27	18	26.4 (2.1)	0.11	75	24.6 (1.0)	0.001	53	19.7 (1.8)	0.04
	P for interaction = 0.04						P for interaction = 0.83
Fish/shellfish intakec (g/day)
T1 (<44.4)	28	28.1 (1.5)		20	22.1 (2.2)		68	21.2 (1.0)		60	17.9 (1.6)
T2 (44.7–<83.0)	34	29.1 (1.3)	0.47	20	24.3 (2.1)	0.11	66	22.8 (1.0)	0.19	56	20.2 (1.8)	0.052
T3 (≥83.0)	38	28.7 (1.4)	0.69	21	26.4 (2.0)	0.006	78	24.7 (1.0)	0.003	40	19.6 (1.8)	0.20
	P for interaction = 0.12						P for interaction = 0.48
Egg intaked (g/day)
T1 (<21.3)	25	28.5 (1.5)		23	25.2 (2.2)		59	21.6 (1.1)		68	17.8 (1.7)
T2 (21.4–<37.8)	28	27.5 (1.5)	0.50	17	24.8 (2.2)	0.78	86	23.1 (0.9)	0.20	40	19.2 (1.8)	0.24
T3 (≥42.4)	47	29.3 (1.2)	0.55	21	26.5 (2.2)	0.41	67	24.1 (1.0)	0.04	48	19.3 (1.7)	0.19
	P for interaction = 0.77						P for interaction = 0.71

^aAdjusted for other variables, excluding intake of fish/shellfish and egg in this table.

^bAs compared with the first category of the variable.

^cAdjusted for other variables, excluding intake of vitamin D and egg in this table.

^dAdjusted for other variables, excluding intake of vitamin D and fish/shellfish in this table.