COVID-19 mortality increases with northerly latitude after adjustment for age suggesting a link with ultraviolet and vitamin D

Dear Editors, We read with interest the review by Dr Kohlmeier in which he reported a correlation between COVID-19 mortality among African-Americans across the USA and northern latitude.1 We previously 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.2 We have now investigated the relationships between latitude, age of population, population density and pollution with COVID-19 mortality. COVID-19 mortality per million by country was downloaded from https://www.worldometers.info/coronavirus/ on 18 May 2020.3 We included all 117 countries with population >1 million and ≥150 COVID-19 cases. Data by country for population %≥65 years, population density and air pollution (particles of matter