No clinically relevant effect on cognitive outcomes after low-dose radiation to the infant brain: A population-based cohort study in Sweden

Figures & data

Figure 1. Inclusion and exclusion criteria in the study.

Figure 2. For each patient the estimated absorbed dose to the anterior brain, the posterior brain and the hippocampus was calculated. The number of subjects in each dose category (mGy) is shown, separated into the anterior brain (green), posterior brain (blue) and the hippocampus (red).

Table I. Estimated absorbed doses (mGy) to different parts of the brain. Cohort for analysis of military tests as outcome.

Part of brain Dose category (mGy)	Anterior			Posterior			Hippocampus
	Number	Mean dose (mGy)	Median dose (mGy)	Number	Mean dose (mGy)	Median dose (mGy)	Number	Mean dose (mGy)	Median dose (mGy)
0	785	0	0	845	0	0	825	0	0
1–20	986	14	10	1000	14	10	765	14	10
21–100	678	48	40	931	56	50	1093	55	50
100–250	437	166	160	171	151	140	256	148	140
250–	144	675	363	83	652	420	91	1105	680
Totals	3030	71	20	3030	48	20	3030	69	20

Figure 3. Results from the Swedish Military Service Conscription Register Data from the cognitive test for the 3030 subjects, separated into the five dose categories. The results are plotted based on the dose to the anterior brain (green), the posterior brain (blue) and the hippocampus (red). The tests results were adjusted for age at treatment and year of birth. The error bars indicate standard error. (A) Results from the logical test. P for trend: anterior 0.12, posterior 0.79 and hippocampus 0.09. (B) Results from the verbal test. P for trend: anterior 0.02, posterior 0.97 and hippocampus 0.005. (C) Results from the spatial test. P for trend: anterior 0.70, posterior 0.58 and hippocampus 0.35. (D) Results from the technical test. P for trend: anterior 0.45, posterior 0.81 and hippocampus 0.18. (E) Combined results from the four tests, yielding a global score. P for trend: anterior 0.23, posterior 0.91 and hippocampus 0.06.

Table II. Higher education in relation to dose, part of the brain and parents’ education. The numbers represent absolute values and in brackets the proportion of individuals with higher education is shown.

Dose (mGy)	No in cohort	Parents without higher education	Parents with higher education
Anterior	2559 (0.25)	2103 (0.19)	456 (0.53)
0	657 (0.27)	510 (0.19)	147 (0.52)
1–20	843 (0.24)	714 (0.18)	129 (0.54)
> 20–100	573 (0.28)	465 (0.22)	108 (0.51)
> 100–250	359 (0.23)	312 (0.20)	47 (0.45)
> 250	127 (0.25)	102 (0.15)	25 (0.68)
Posterior	2559 (0.25)	2103 (0.19)	456 (0.53)
0	710 (0.27)	550 (0.19)	160 (0.52)
1–20	856 (0.24)	727 (0.18)	129 (0.54)
> 20–100	776 (0.26)	639 (0.21)	137 (0.48)
> 100–250	153 (0.24)	134 (0.19)	19 (0.63)
> 250	64 (0.27)	53 (0.17)	11 (0.73)
Hippocampus	2559 (0.25)	2103 (0.19)	456 (0.53)
0	696 (0.27)	541 (0.20)	155 (0.53)
1–20	653 (0.25)	551 (0.19)	102 (0.56)
> 20–100	923 (0.24)	769 (0.19)	154 (0.47)
> 100–250	208 (0.28)	175 (0.22)	33 (0.64)
> 250	79 (0.24)	67 (0.16)	12 (0.67)

Table III. Odds ratios and 95% confidence intervals of higher education, in relation to dose.

Dose (mGy)	Crude odds ratio (95% CI)	Multivariate* odds ratio (95% CI)
Anterior	n = 2559	n = 2559
0	1.00	1.00
1–20	0.86 (0.68–1.09)	0.97 (0.75–1.24)
> 20–100	1.05 (0.82–1.35)	1.09 (0.83–1.42)
> 100–250	0.84 (0.62–1.13)	0.97 (0.70–1.33)
> 250	0.93 (0.60–1.44)	0.88 (0.56–1.41)
Odds ratio per 50 mGy	0.99 (0.97–1.02)	0.99 (0.97–1.02)
Posterior	n = 2559	n = 2559
0	1.00	1.00
1–20	0.86 (0.68–1.08)	0.97 (0.76–1.23)
> 20–100	0.96 (0.76–1.21)	1.02 (0.79–1.30)
> 100–250	0.87 (0.65–1.31)	1.00 (0.65–1.54)
> 250	0.99 (0.55–1.77)	1.02 (0.55–1.89)
Odds ratio per 50 mGy	0.99 (0.95–1.02)	0.99 (0.95–1.02)
Hippocampus	n = 2559	n = 2559
0	1.00	1.00
1–20	0.90 (0.70–1.15)	1.00 (0.77–1.30)
> 20–100	0.85 (0.68–1.07)	0.91 (0.71–1.15)
> 100–250	1.07 (0.76–1.51)	1.18 (0.82–1.69)
> 250	0.86 (0.50–1.47)	0.88 (0.50–1.55)
Odds ratio per 50 mGy	1.00 (0.99–1.02)	1.00 (0.99–1.02)

*Adjusted for age at treatment, year at birth and parents’ education.