TABLE 4.

Associations of serum 25(OH)D₃ concentration in an unrelated subset of Alaska Native (Yup’ik) people¹

		Full model
Characteristic	n	β-Coefficient2	P	Variability explained,3R2
Fully adjusted model4	526			(0.53)
Age5				(0.34)
<20 y			Ref
20–39 y		2.7 ± 1.1	7.1 × 10−3
40–59 y		8.6 ± 1.3	2.7 × 10−10
>59 y		12.5 ± 1.6	6.6 × 10−13
Season				(0.10)
May–July	150	−4.9 ± 1.2	9.9 × 10−6
August–October	136		Ref
November–January	207	−4.1 ± 1.0	2.6 × 10−5
February–April	33	−6.9 ± 1.9	8.9 × 10−4
RBC log10(δ15N value)6		5.0 ± 0.5	<2 × 10−16	(0.21)
Gender				(0.00)
Male	282	2.3 ± 0.9	7.1 × 10−3
Female	244		Ref
Village location				(0.06)
Coastal	270	7.6 ± 0.9	1.6 × 10−15
Inland	256		Ref
BMI7		−0.6 ± 0.5	0.13	(0.01)
CYP2R1 rs11023374				(0.02)
Homozygous variant	23	−4.5 ± 2.0	1.5 × 10−2
At least 1 reference allele	503		Ref
Age and RBC log10(δ15N value)8				(0.37)

¹Variability in 25(OH)D₃ concentration is explained by predictors in a multiple linear regression. Participants included in this regression represent an unrelated subset (n = 526) of the overall data set (n = 743). This subset included only individuals unrelated to the third degree, as determined by using pedigree information. The significance of the association of each variable with 25(OH)D₃ concentration is indicated by the P value and determined by using a likelihood ratio test. β-Coefficients for categorical data represent change in serum 25(OH)D₃ concentration between a category and its reference group. β-Coefficients for continuous data represent change in serum 25(OH)D₃ concentration for a change of 1 SD in the continuous variable. The δ¹⁵N value is a biomarker of traditional food intake as defined in Methods. CYP2R1, cytochrome P450 family 2, subfamily R, peptide 1; Ref, reference category for all discrete variables; 25(OH)D₃, 25-hydroxycholecalciferol.

²Values are β-coefficients ± SEs from a multiple linear regression model. β-Coefficients are determined as change in serum 25(OH)D₃ concentration (ng/mL) per unit of change in the predictor variable, when all other predictor variables are held constant.

³The goodness of fit of a multiple linear regression, on a scale of 0 to 1, as reflected in the R² value.

⁴The fully adjusted model of serum 25(OH)D₃ concentration as the outcome variable and including all predictors in the table: age (NHANES grouping), season of sample collection, RBC log₁₀(δ¹⁵N value), gender, village location, BMI, and genotype at CYP2R1 rs11023374.

⁵Linear regression was used to regress each listed predictor individually with outcome data of serum 25(OH)D₃ concentration. These predictors in each model are listed.

⁶Values for the RBC log₁₀(δ¹⁵N value) reflect change in serum 25(OH)D₃ concentration per 1 SD of log₁₀(δ¹⁵N values). The SD of the log₁₀(δ¹⁵N values) is 0.0595.

⁷Values for BMI reflect change in serum 25(OH)D₃ concentration per 1 SD of BMI. The SD of the BMI is 5.67.

⁸Multiple regression model of 25(OH)D₃ concentration outcome and including 2 predictors: RBC log₁₀(δ¹⁵N value) and age, divided into NHANES categories.