Table 3. Iron biomarkers and trajectories of MSEL cognitive score.

	Unadjusted*				Effect Size	Adjusted**				Effect Size
	Coeff	P value	Age interaction	P value		Coeff	P value	Age interaction	P value
Ferritin
Low base group)
Med	0.08	0.902	-0.05	0.532	0.02	0.44	0.540	-0.08	0.326	0.11
High	0.25	0.709	-0.02	0.793	0.06	-0.37	0.594	0.04	0.621	0.10
Hb
Low (base group)
Med	-0.92	0.157	0.15	0.034	0.23	-0.95	0.176	0.19	0.017	0.24
High	0.48	0.481	0.10	0.145	0.12	0.49	0.502	0.07	0.377	0.12
sTfR
High (base group)
Med	1.39	0.031	-0.09	0.198	0.35	1.28	0.069	-0.02	0.779	0.33
Low	2.00	0.003	-0.03	0.658	0.51	1.89	0.009	-0.01	0.982	0.48

Hb; haemoglobin.

sTfR; soluble transferrin receptor.

Low/ Med/ High represent terciles of each biomarker; low = lowest tercile, med = middle tercile, high = highest tercile. Higher haemoglobin and higher ferritin both indicate better status whereas higher sTfR indicates poorer status. For each biomarker the tercile representing poorest status was used as the base group (Ferritin base = Low, Hb base = low, sTfR base = high). The co-efficients in each row of the table therefore represent the comparison between the base group and the group named in the first column.

*Unadjusted models included age terms (age & age³), biomarker terciles, biomarker-age interaction terms for Terciles included in the model and log c-reactive protein. Observations included = 837, Infants included = 177, mean observations per infant = 4.7.

** (S3–S5 Tables). In addition to the variables included in the unadjusted models, adjusted models included sex, Fourier terms for seasonality, infant height, infant gestational age at birth and maternal education. Full details are available in the Supplementary Methods. Observations included = 430, infants included = 110, mean observation per infant = 3.9.

Effect Size = (group difference/ Standard deviation of base group).