Table 2.

Descriptive statistics for all different exposure variables used in linear regression models for the whole sample and the five media use groups separately.

Variable	Total			Low use			Media usea			Gaming			Call preference			High social use
	n	$\text{mean}\pm \text{SD}$	IQRb	n	$\text{mean}\pm \text{SD}$	IQR	n	$\text{mean}\pm \text{SD}$	IQR	n	$\text{mean}\pm \text{SD}$	IQR	n	$\text{mean}\pm \text{SD}$	IQR	n	$\text{mean}\pm \text{SD}$	IQR
Whole sample
Verbal memory scorec
Baseline	751	$4.9\pm 2.8$	4.0	196	$5.3\pm 2.7$	3.5	191	$4.8\pm 2.7$	4.0	88	$4.8\pm 2.8$	3.5	110	$4.8\pm 2.8$	4.0	166	$4.6\pm 3.0$	5.0
Follow-up	738	$5.9\pm 2.7$	4.0	187	$6.5\pm 2.6$	5.0	193	$5.9\pm 2.8$	4.0	84	$5.5\pm 2.7$	4.0	110	$5.8\pm 2.8$	4.0	164	$5.6\pm 2.8$	4.0
Difference ($\text{follow}\text{-up}–\text{baseline}$)	676	$1.1\pm 3.0$	4.0	180	$1.3\pm 2.9$	4.0	168	$1.0\pm 3.0$	4.0	78	$0.8\pm 2.7$	3.0	106	$1.2\pm 2.9$	4.0	144	$1.2\pm 3.3$	4.5
Figural memory scorea
Baseline	740	$7.8\pm 2.8$	4.0	195	$8.5\pm 2.5$	3.0	189	$7.3\pm 2.8$	4.0	86	$6.9\pm 2.7$	4.0	110	$8.1\pm 2.7$	4.0	160	$7.6\pm 3.1$	4.0
Follow-up	742	$7.9\pm 3.3$	6.0	189	$8.5\pm 3.2$	5.0	194	$8.0\pm 3.2$	5.0	85	$6.8\pm 3.5$	6.0	110	$7.5\pm 3.3$	5.0	164	$7.7\pm 3.5$	6.0
Difference ($\text{follow}\text{-up}–\text{baseline}$)	670	$0.2\pm 3.2$	4.0	180	$0.1\pm 2.8$	4.0	168	$0.7\pm 3.0$	4.0	77	$-0.3\pm 3.6$	6.0	106	$-0.5\pm 3.2$	5.0	139	$0.5\pm 3.6$	5.0
Usage related to EMF exposure to the head
Cordless phone calls [$\text{min}/\mathrm{d}$]	843	$6.2\pm 6.6$	5.1	207	$6.0\pm 5.6$	5.1	223	$4.7\pm 4.1$	4.0	97	$4.0\pm 3.6$	2.3	119	$10.8\pm 9.6$	11.3	197	$6.5\pm 7.6$	5.1
Mobile phone calls [$\text{min}/\mathrm{d}$]d	843	$10.6\pm 13.7$	12.6	207	$5.9\pm 7.7$	7.4	223	$9.0\pm 12.8$	10.2	97	$9.9\pm 12.3$	15.7	119	$15.9\pm 11.9$	13.2	197	$14.4\pm 18.4$	15.3
Mobile phone calls, self-reported [$\text{min}/\mathrm{d}$]	843	$17.2\pm 27.6$	16.3	207	$7.3\pm 10.9$	7.0	223	$11.4\pm 19.1$	9.9	97	$13.8\pm 34.5$	9.4	119	$31.1\pm 35.8$	27.5	197	$26.7\pm 32.1$	27.4
Usage marginally related to EMF exposure to the head
Data traffic [$\text{min}/\mathrm{d}$]	843	$56.7\pm 34.3$	55.4	207	$27.6\pm 25.2$	35.5	223	$51.3\pm 28.3$	43.4	97	$59.2\pm 30.5$	44.7	119	$66.7\pm 26.5$	41.4	197	$86.1\pm 27.3$	44.8
Gaming [$\text{min}/\mathrm{d}$]	843	$43.0\pm 56.9$	55.7	207	$38.6\pm 48.6$	51.3	223	$20.9\pm 33.9$	29.3	97	$116.1\pm 63.2$	63.6	119	$49.6\pm 62.0$	56.8	197	$32.7\pm 50.2$	40.0
Texts sent [$\text{number}/\mathrm{d}$]	843	$35\pm 21$	40	207	$15\pm 12$	17	223	$32\pm 18$	30	97	$36\pm 20$	35	119	$43\pm 17$	24	197	$54\pm 12$	13
Cumulative brain dose [$\text{mJ}/\mathrm{kg}\text{per}\text{day}$]e	830	$858\pm \mathrm{1,027}$	953	198	$551\pm \mathrm{1,029}$	471	221	$753\pm 824$	800	97	$806\pm 956$	997	118	$\mathrm{1,214}\pm \mathrm{1,259}$	1,391	196	$\mathrm{1,098}\pm \mathrm{1,003}$	1,110
Sample with operator data
Duration mobile phone calls [$\text{min}/\mathrm{d}$]	322	$3.2\pm 13.3$	1.8	116	$1.1\pm 2.9$	0.8	63	$4.2\pm 4.1$	1.7	30	$1.7\pm 3.1$	1.2	65	$2.8\pm 3.8$	2.7	48	$8.8\pm 29.2$	8.0
Cumulative brain dose [$\text{mJ}/\mathrm{kg}\text{per}\text{day}$]e	318	$469\pm 814$	341	115	$357\pm 918$	187	61	$465\pm 638$	324	30	$344\pm 694$	152	65	$620\pm 793$	517	47	$607\pm 842$	443

Note: EMF, electromagnetic field; IQR, interquartile range; SD, standard deviation.

^aMedia use groups were determined by latent class analysis on 11 qualitatively different media use variables as described in Foerster and Röösli (2017).

^bUser-group–specific IQRs are displayed for descriptive purposes. For reporting user-group–specific IQRs (see Figure S2), the whole population IQR was used.

^cDue to technical problems with the computerized testing system, completed tests for both time points were only available for a reduced number of participants.

^dAdjusted via multilevel linear regression estimates calibrated on the objectively recorded duration of calls obtained by mobile phone operators. Models were clustered over schools and the following predictors were selected from the self-reported questionnaire data: age, gender, daily frequency of mobile phone calls at follow-up, daily frequency of text messages at follow-up, daily duration of mobile phone data traffic at follow-up, daily duration of cordless phone calls at follow-up, difference in daily duration of mobile phone calls between follow-up and baseline.

^eCumulative brain dose derived based on the following cumulative exposure variables. Near-field bands (if not indicated otherwise, taken from the questionnaire): daily duration of mobile phone calls (for the whole sample: calibrated via operator data; for the operator sample: operator recorded), network proportions of UMTS and GSM (for the whole sample: calibrated via operator data and far-field UMTS proportion; for the operator sample: operator recorded), proportion of headset use, daily duration of cordless phone calls, daily duration of mobile phone data traffic on WiFi and 3G, daily duration of WiFi use via laptop, PC, and tablet, daily duration of mobile phone held close to body; far-field bands: Uplink from surrounding mobile phones and Wifi (modeled via linear regression estimation based on questionnaire and personal measurements), downlink GSM900, downlink GSM1800, downlink UMTS, radio/broadcast, TV [(determined by geospatial propagation modeling using the NISMap software (Bürgi et al. 2010)], DECT (mean of the measurements).