Analysis	Description	Background and rationale
Sensitivity analyses
1	Account for airborne emissions by redefining the exposure as living in a zone around a NPP that is equivalent in area to a circle with 5 km radius, but extends to a distance proportional to the average duration of slow winds (<3 m/s) in a given direction.a,b	Stronger associations in this analysis compared with the main analysis would support a causal effect of airborne emissions from NPPs (radionuclides or other). Downwind concentrations of pollutants are inversely related to wind speed.34 We therefore defined an exposure zone based on the direction of slow winds.
2	Exclude children living >50 km from a NPP.	Concentration of emissions from NPPs decrease rapidly with distance and will be virtually zero at distances >50 km. Regional differences in incidence rates in children living >50 km from NPPs, which are not related to emissions from NPPs, could have introduced bias.
3	Exclude calendar years 1985–90 and 2009.	Registration in the SCCR was less complete in 1985–90 and 2009.
4	Exclude children born abroad or before 1985 from the resident cohort.	Differences between the results for the birth and resident cohort might be due to the fact that the birth cohort includes only children born in Switzerland ≥1985, whereas the resident cohort also includes children born <1985 and children who were born abroad. This sensitivity analysis eliminates the difference in the two study populations.
5	Use an alternative method to calculate person-years.a	The main analysis calculates person-years for a particular age group and calendar year based on the number of children of the same age in the two census years. The alternative method uses the number children belonging to the same cohort in the census years instead.
6	Recalculate distance to nearest NPP by excluding each NPP in turn.	To investigate whether results were influenced by the characteristics of a particular NPP. Beznau I & II and Leibstadt are excluded together because of their proximity to each other.
7	Stratify the analysis by calendar period (1985–94 and 1995–2009).	All NPPs were in operation 1985–2009. Differences in results between the earlier and later periods might indicate confounding by unknown time-varying factors, or changes in emissions over time.
8	Include only children who remained in the same community since birth.b	Families with children at greater risk of developing cancer may have preferentially relocated closer or further away from NPPs as the children grew older. This could have affected results when using addresses at diagnosis, compared with addresses at birth.
Additional analyses
9	Use 1/(distance in km) as a continuous exposure variable.	To avoid the loss of information caused by categorising the exposure variable. According to an atmospheric dispersion model, air concentrations of radionuclides are approximately proportional to (distance in km)−1.4.34 We chose (distance in km)−1 for comparability with previous studies.4,5
10	Perform a direct comparison of distances to nearest NPPs between cases and the population at risk using two-sample t-tests and the Mann–Whitney U-test. We used addresses at birth of cases born in 1988–92 and 1998–2002 and addresses of infants in the 1990 and 2000 census populations. Only distances <50 km were included.b	This analysis avoids computation of person-years; rather it uses the directly observed distances of the population at risk in the census years. It also avoids categorising the exposure variable as in analysis (9), but unlike (9), no assumptions about the relationship between distance to NPPs and cancer incidence are made.

^aFurther details given in Supplementary Appendix 1, available as Supplementary Data at IJE online.

^bFurther details given in Supplementary Appendix 2, available as Supplementary Data at IJE online.