Sunshine might play a key role in warding off the worst effects of Covid-19, according to a University of Edinburgh study.
The research, published in the British Journal of Dermatology, found increased exposure to the sun’s rays – specifically UVA – was associated with reduced deaths from the virus.
Researchers compared all recorded deaths from Covid-19 in the US from January to April 2020 with UV levels for 2,474 counties for the same time period.
They found that people living in areas with the highest level of exposure to UVA rays had a lower risk of dying from Covid-19 compared with those with lower levels. The results were the same in England and Italy, too.
The reduction in risk of death from Covid-19 could not be explained by higher levels of vitamin D, experts said – it was more likely to be as a result of the sun’s UV rays.
Dr Richard Weller, study author, consultant dermatologist and reader at the University of Edinburgh, said: “These early results open up sunlight exposure as one way of potentially reducing the risk of death.”
One explanation for the link between UVA rays and reduced Covid deaths is that sunlight exposure causes the skin to release nitric oxide, researchers said. This may reduce the ability of the virus that causes Covid-19 to replicate, as has been found in some lab studies.
Previous research from the same research group has shown that increased sunlight exposure is linked to improved cardiovascular health, with lower blood pressure and fewer heart attacks. As heart disease is a known risk factor in dying from Covid-19, this could also explain the latest findings.
Of course, that doesn’t mean you should – or even could – sunbathe all day to ward off the virus. We know that overexposure to UVA and UVB rays from the sun carries its own risks including sunburn, premature ageing and skin cancer, which can be deadly.
Wearing sunglasses with a UV light filter, using a sunscreen with a high protection factor (SPF 30 minimum), and staying out of the sun during the hottest part of the day (between 11am and 3pm) will help you enjoy the sun safely, Macmillan Cancer Support advises.
The research team caution that due to the observational nature of the study, it is not possible to establish cause and effect. However, it might lead interventions that could be tested as potential treatments.
Professor Chris Dibben, chair in health geography at the University of Edinburgh and study co-author, said: “The relationship between Covid-19 mortality, season and latitude has been quite striking, here we offer an alternative explanation for this phenomenon.”
Previous studies have found exposure to sunshine can kill off the virus quickly on surfaces. A study published in the Journal of Infectious Diseases found that most coronavirus particles deactivated within 10 minutes when exposed to ultraviolet light from the midday sun.
In conditions mimicking the winter sun in Spain, 90% of particles were destroyed in less than 15 minutes, while in conditions simulating summer sun, the virus lasted 6.8 minutes, the Times reported.
It had previously been suggested that the virus could last on surfaces for up to 72 hours, making this a significant reduction.