COVID-19, vitamin D and latitude – Update

Emeritus Professor of Medicine Jonathan M Rhodes, University of Liverpool’s Department of Cellular and Molecular Physiology

Dr Sreedhar Subramanian, University of Liverpool’s Department of Cellular and Molecular Physiology

Emeritus Professor of Statistics, Frank Dunstan, School of Medicine, Cardiff University
Eamon Laird, The Irish Longitudinal Study on Ageing, School of Medicine, Trinity College Dublin

Professor Rose Anne Kenny, Department of Medical Gerontology, Mercers Institute for Ageing, St James Hospital

“We have published a letter in BMJ Nutrition, Prevention & Health that highlights the association between COVID-19 mortality by country and latitude.

Previously we reported a north–south gradient in global COVID-19 mortality but were conscious that lack of ultraviolet exposure and consequent vitamin D insufficiency was not the only possible explanation.

We have now investigated the relationships between latitude, age of population, population density and pollution with COVID-19 mortality.

Our study showed a 4.9% increase in mortality for each 1 degree latitude further north from a latitude of 28 degrees. This strongly suggests an effect of ultraviolet light, most plausibly mediated via its effect on vitamin D synthesis in the skin.

This complements our previous report based on a simpler analysis. It shows that, although much of the association between latitude and mortality can be accounted for by differing ages of populations, there remains a significant association after this has been taken into account.

We conclude that whilst this does not prove causation it supports the hypothesis that vitamin D deficiency may increase the severity of COVID-19.”

The full letter, entitled ‘COVID-19 mortality increases with northerly latitude after adjustment for age suggesting a link with ultraviolet and vitamin D’, can be found here.