Higher Scores of Ambient Temperature, Sunshine Hours and UV Index are Associated with Lower COVID-19 Mortality

Following two years of the COVID-19 pandemic, thousands of deaths were registered around the world. A question on whether climate parameters in each country could or not affect coronavirus incidence and COVID-19 death toll is under debate.

In this work, we aimed to analyse possible relation between the prevalence of COVID-19 deaths and the geographic latitude. The study focused on the geographic latitudes and some of their associated climate factors, such as the average annual level of temperature, sunshine hours and UV index.

We sought the number of the deaths caused by COVID-19 in 39 countries. Latitude levels were plotted against the average annual levels of either temperature, sunshine hours or UV index. Data were analysed by simple linear regression or polynomial regression, by means of Microsoft Excel software (2016).

When COVID-19 death numbers were plotted against geographic latitudes, we obtained inverted bell-shaped curves, for both the first and second year of the pandemic, with a coefficient of determination of (R² = 0,32) and (R² = 0,39), respectively. In addition, COVID-19 death numbers were very negatively correlated with the average annual levels of temperature (R² = 0,52, P= 4.92x10^-7), sunshine hours (R² = 0,36, P= 7.68x10^-6) and UV index (R² = 0,38, P= 4.16x10^-5). Bell-shaped curves were obtained when latitude was plotted against the average annual number of temperature, sunshine hours and UV index, with a coefficient of determination of (R² = 0,85), (R² = 0,452) and (R² = 0,87), respectively.

In contrast to high-latitude countries, countries located at low latitudes may have suffered less COVID-19 death tolls, thanks to their elevated temperature, sunshine hours and UV index. The above climate factors, in addition to yet unknown factors, could have impaired the spread of the coronavirus and/or helped individual’s natural immunity to fight COVID-19 disease.