Footnotes

• Contributors Both authors drafted this letter by making multiple iterations.

• Competing interests TS is Principal Investigator of a cohort mortality study of workers in the UK electricity supply industry and receives research funding from the Energy Networks Association (ENA), a trade association. JS is employed by National Grid and worked on this letter as part of his employment, but no approval was required or sought from anyone else in the Company.

• Patient consent Not relevant. The letter does not concern human subjects, it is a comment on methodology.

• Provenance and peer review Not commissioned; internally peer reviewed.