Sir,

I read with interest the article by Guggenheim et al1 describing the relationship between febrile illness in childhood and myopia.

UK Biobank collected data on 502 649 subjects, aged 37 to 73, during 2006 to 2010. Febrile illness history was ascertained during the face-to-face interview, when participants self-reported cancer and non-cancer illnesses, including the date of diagnosis by a doctor. The available illness-response terms included pneumonia, encephalitis, meningitis, rheumatic fever, measles, rubella, mumps, diphtheria, and pertussis.

A total of 91 592 participants with visual acuity data were included in the analysis.

The figures on page 4 report the number of cases of these conditions in this group.

During the childhood of most of the Biobank participants, between 150 000 and 800 000 cases of measles were reported each year in England and Wales,2 and in 1963, 150 of every 1000 children were reported as having measles. So it seems unlikely that the proportion in Biobank ever reporting measles would be 0.72%.

The main Biobank website3 reports 2737 reporting measles in 378 597 participants, again 0.72%. In addition, 61 147 (16%) with asthma, 5893 (1.6%) with rheumatoid arthritis, and 15 761 (4.2%) people with fractures were reported.