Table 2.

Related factors with vitamin E levels with multivariable linear regression model.

Factors	β	95%CI	p
Age	0.004	0.0037 to 0.0042	<0.001
Season
Spring	−0.002	−0.006 to 0.0008	0.146
Summer	−0.028	−0.031 to −0.024	<0.001
Autumn	−0.013	−0.017 to −0.010	<0.001
Winter	ref
Gestational trimester
1st trimester	ref
2nd trimester	0.088	0.085–0.091	<0.001
3rd trimester	0.154	0.151–0.156	<0.001
Region
Shaanxi	−0.030	−0.035 to −0.026	<0.001
Ningxia	−0.063	−0.069 to −0.057	<0.001
Qinghai	−0.027	−0.032 to −0.022	<0.001
Shanxi	ref

The four seasons are defined by date: spring, from March to May; summer, from June to August; autumn, from September to November; winter, from December to February.