Yet Another Sunlight Benefit in the Battle Against Covid-19?

Pure gold? Or perhaps just a flash in the pan ....

Is Donald Trump REALLY smarter than we thought? Following that theme line a bit further ...

"There are three kinds of lies: lies, damned lies, and statistics." Mark Twain

A recent paper that was published in the British Journal of Dermatology (BJD) by Mark Cherrie and colleagues at the University of Edinburgh shows a statistically-significant association between death rates from COVID-19 and regional differences in the daily ambient UVA. Similar correlations are found in three countries (USA, UK, and Italy) despite large differences in their mortality rates.

The study covers the initial three months of the pandemic, and is restricted to situations where the production of vitamin-D from sunlight in that winter period is small. The authors argue that despite those low levels of UVB, there’s still enough UVA present to affect the release of nitric oxide from the skin - and that differences between regions were sufficient to reveal the association. They postulate that the resulting elevated levels of nitric oxide in the blood due to higher UVA lead to better outcomes through its ability to lower blood pressure, and through its possible effects on the ability of the COVID-19 virus to self-replicate.

While interesting, and potentially important in the ongoing battle against COVID-19 (and its variants) there are other possible explanations for their observed association. While several were explored in the analysis, doubts will remain despite the statistical significance found by the model.

The editors of BJD asked me to write a “Commentary” on the paper. It’s now available on line, and will appear in this month’s issue of the printed version. Full marks to the journal’s publishers - Wiley Publishing. In the public’s interests they’re are waiving the on-line publication charges for COVID-related papers. Normally they’d be hiding our paper behind a paywall unless we’d come up a ransom of about US$4,200. At today’s exchange rate that’s about NZ$5,800, close to NZ$8 per word, which is about NZ$8 per word more than I received for doing the work!! Notwithstanding the old adage that “free advice is worth what you paid for it”, I’d already decided to provide a short free summary here, hopefully in terms understandable by the layman.

So here it is …

As we say in our Commentary, for many the paper will raise more questions than it answers.

A few examples:

1. Could the observed association really result from much more direct effect of UV on the outdoor survival of COVID-19, that I discussed earlier (since verified).

2. Is the ambient UV exposure from sunlight a good enough proxy for personal exposure? Our own study involving hundreds of participants using personal dosimeter badges found that they typically received less than 3% of the ambient UVB, showing that most of their time was not spent outside. In the case of UVA, it’s further confounded by the availability of indoor radiation. With modern work environments - and total lock-downs over the period interest - the total received UVA exposure may be only weakly dependent on the contribution from sunlight.

3. With the benefit of hindsight, we now know that factors other than UV - including political mismanagement - play a part in waves of infection (and mortality). Could regional differences in the phasing of waves of infection be confused with the strong seasonal increase in UV over the period of study.

   

4. Can the statistical model really differentiate between the possible benefit from UV-A in sunlight (through production of nitric oxide) compared with the possible benefit from UVB in sunlight (through its production of vitamin-D)? The figure below shows that the two are highly correlated, with more than 93 percent of the variance in one being attributable to variance in the other.

Correlation between UVA and UVB derived from spectral irradiance measurements at Lauder New Zealand.  Data points from the 4 winter months corresponding in the study are highlighted.

Because of the ongoing risk from COVID-19, there will be justifiably strong interest in the paper. But more work on the subject is definitely warranted. A key question will be whether the association still hangs together another 12 months down the track.

Could this explain Donald Trump’s miraculous recovery from his supposed bout of COVID-19 last year? 😊 His unnaturally yellow skin can’t the result of a cosmetic skin application. He could surely afford a better colour than that. Could it attest to frequent exposures to UVA in sunbeds? He’s certainly silly enough to subject his body to the risks that entails - though the white strip around his eyes shows he apparently does have the sense to cover them (unlike when he views solar eclipses).

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Thanks for getting this far! Previous posts on the intersection between Ozone, UV, Climate, and Health can be found at my UV & You area at Substack. Click below to subscribe for occasional free updates.