People who live in sunnier areas may have a lower risk of dying from the coronavirus, according to a new study carried out in the US and replicated in Italy and England.
Researchers compared COVID-19 deaths with ultraviolet (UV) levels for the same period and found that sunnier areas were associated with fewer deaths.
The study, published in The British Journal of Dermatology, found that the Mortality Risk Ratio – the ratio between the likelihood of dying for a certain population group and the risk of death for all other population groups – in the US fell 29% for every 100 kilojoules per square meter increase in mean daily ultraviolet light. In Italy and England, there was an estimated pooled decline of 32%.
Researchers are examining what could be behind this correlation. One possible explanation is that nitric oxide is released by the skin when it is exposed to sunlight. Some studies suggest that the skin’s release of nitric oxide may reduce the ability of the SARS Coronavirus2 to replicate, the article said.
Another possible explanation is that other studies have shown increased exposure to sunlight is associated with fewer heart attacks and lower blood pressure, both factors that could possibly reduce the risk of dying from COVID-19.
This reduced risk could not be explained by vitamin D levels in the local population, according to the research. This is because the research was based in areas where UVB (type B ultraviolet) levels are too low to produce significant vitamin D levels in the body.
The study accounted for other known risk factors related to exposure and an increased risk of COVID death, including age, socioeconomic status, ethnicity, levels of infection in the area, air pollution and temperature.
Because the study was observational, it could not establish cause and effect. But researchers say if further studies determine that there is a causal effect, sunlight could act as a simple public health intervention.
“These early results open up sunlight exposure as one way of potentially reducing the risk of death,” said Dr. Richard Weller, a corresponding author, consultant dermatologist and reader at the University of Edinburgh.
The new study may be particularly relevant to Israel, which is a sunny country with a high UV index.