Table 3.

Parameter Estimates from GEE Models for Receiving Vitamin D Supplementation and Meeting the Vitamin D Recommendation (10 mcg/day) Among Infants Enrolled in WIC. Presented as OR (95% CI) P-value.^1–2

Independent variables	Category	Outcome
		Receiving vitamin D supplementation		Meeting vitamin D recommendation (10 mcg/day)
Time of visit	1 month	Reference		Reference
	3 month	1.11 (0.86, 1.43)	0.42	1.21 (0.95, 1.55)	0.12
	5 month	1.11 (0.83, 1.47)	0.49	1.24 (0.93, 1.65)	0.14
	7 month	0.84 (0.62, 1.14)	0.26	0.97 (0.72, 1.30)	0.82
	9 month	0.69 (0.48, 1.00)	0.05	0.79 (0.55, 1.13)	0.19
	11 month	0.67 (0.44, 1.02)	0.06	0.83 (0.56, 1.24)	0.37
	13 month	0.45 (0.29, 0.70)*	< 0.001	0.78 (0.53, 1.15)	0.21
Feeding type	Breastmilk	Reference		Reference
	Formula	0.34 (0.25, 0.46)*	< 0.001	0.92 (0.68, 1.23)	0.56
	Both	0.70 (0.49, 1.00)*	0.05	0.75 (0.51, 1.09)	0.13
	Neither	0.50 (0.31, 0.79)*	0.003	3.81 (2.67, 5.44)*	< 0.001
Maternal age, years	16–19	Reference		Reference
	20 – 25	0.90 (0.58, 1.40)	0.64	0.88 (0.73, 1.06)	0.19
	≥26	1.43 (0.87, 2.36)	0.16	1.02 (0.83, 1.27)	0.83
Education level, grade	≤9th	Reference		Reference
	10th–11th	0.95 (0.62, 1.46)	0.82	0.92 (0.73, 1.15)	0.46
	12th	1.20 (0.79, 1.82)	0.38	0.93 (0.75, 1.15)	0.49
	>12th	1.41 (0.92, 2.17)	0.11	0.87 (0.70, 1.08)	0.21
Maternal nativity	USA born	Rference		Reference
	Not USA born	1.45 (1.11, 1.89)*	0.006	0.96 (0.82, 1.12)	0.59
Parity	1st born	Reference		Reference
	2nd born	0.72 (0.56, 0.94)*	0.01	1.12 (0.97, 1.30)	0.13
	3rd or subsequent born	0.56 (0.42, 0.74)*	< 0.001	1.13 (0.96, 1.32)	0.13
Child sex	Male	Reference		Reference
	Female	0.98 (0.80, 1.20)	0.89	0.80 (0.71, 0.89)*	< 0.001
Maternal race/ethnicity	Non-Hispanic White	Reference		Reference
	Hispanic	0.91 (0.70, 1.18)	0.48	1.02 (0.88, 1.18)	0.81
	Non-Hispanic Black	1.29 (0.95, 1.75)	0.10	1.43 (1.23, 1.67)*	< 0.001
	Non-Hispanic Other	1.03 (0.67, 1.58)	0.91	1.57 (1.21, 2.02)*	< 0.001
Household poverty level	≤75%	Reference		Reference
	>75% and ≤130%	1.31 (0.97, 1.76)	0.08	0.96 (0.84, 1.10)	0.62
	>130%	1.16 (0.90, 1.48)	0.25	1.05 (0.87, 1.28)	0.60
Time of Visit & feeding type interaction 3	1 month*breastmilk	Reference		Reference
	1 month*formula	1		1
	1 month*both	1		1
	3 month*breastmilk	1		1
	3 month*formula	0.77 (0.52, 1.14)	0.20	2.04 (1.46–2.84)*	< 0.001
	3 month*both	0.87 (0.56, 1.35)	0.52	1.11 (0.72, 1.71)	0.64
	5 month*breastmilk	1		1
	5 month*formula	0.68 (0.44, 1.04)	0.07	2.90 (1.99, 4.22)*	< 0.001
	5 month*both	0.62 (0.37, 1.05)	0.08	1.04 (0.63, 1.71)	0.87
	7 month*breastmilk	1		1
	7 month*formula	0.69 (0.45, 1.07)	0.10	2.27 (1.53, 3.38)*	< 0.001
	7 month*both	0.75 (0.44, 1.28)	0.30	1.01 (0.61, 1.70)	0.96
	7 month*neither	0.42 (0.21, 0.83)*	0.01	0.77 (0.35, 1.68)	0.51
	9 month*breastmilk	1		1
	9 month*formula	0.89 (0.55, 1.44)	0.63	2.33 (1.50, 3.63)*	< 0.001
	9 month*both	0.80 (0.43, 1.50)	0.49	1.42 (0.77, 2.59)	0.26
	9 month*neither	0.67 (0.23, 1.94)	0.46	0.47 (0.22, 1.00)	0.05
	11 month*breastmilk	1		1
	11 month*formula	0.94 (0.55, 1.59)	0.81	2.12 (1.33, 3.40)*	0.002
	11 month*both	1.11 (0.54, 2.31)	0.78	1.37 (0.68, 2.74)	0.37
	11 month*neither	1.13 (0.45, 2.88)	0.79	1.02 (0.58, 1.80)	0.94
	13 month*breastmilk	1		1
	13 month*formula	1.57 (0.78, 3.15)	0.21	2.75 (1.69, 4.48)*	< 0.001
	13 month*both	1.28 (0.51, 3.18)	0.60	1.81 (0.73, 4.54)	0.20
	13 month*neither	1		1

WIC: Special Supplemental Nutrition Program for Women, Infants, and Children; GEE: Generalized estimating equation; OR: Odds ratio, CI: Confidence Interval, mcg: microgram

¹Number of participants in the GEE model = 3,830

^2*P < 0.05 after Bonferroni adjustment applied

³Interactions ORs refer to the ratios of ORs and were used to calculate the marginal ORs. For example, for 3-month-old infants, the odds for “formula fed” infants meeting the recommendation was 0.92 (formula fed vs. breastfed) × 2.04 (3 month*formula) = 1.88 times the odds for “breastfed” infants meeting the recommendation, controlling for all other variables.