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NaturistDoc
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Posted - 03/05/2020 : 02:47:18 AM
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At last! At long last Dr. Weller's study has been published, and it is indeed large, involving some 342,457 patients. It asks (and purports to answer) the question, "Does Incident Solar Ultraviolet Radiation Lower Blood Pressure?" The article has already found its way into the mass media via, once again, 'Outside' magazine. His answer is, of course, "Yes", but I'm not at all sure I agree.
Weller et al rather astutely used a database of kidney dialysis patients, since these folks get their blood pressure measured very frequently at dialysis centers by trained personnel who know how to work a blood pressure cuff. But one could reasonably ask if kidney failure patients are a fair representation of the population at large. That is only one of the problems I have with Dr. Weller's paper.
First let's look at the overall results, shown in Figure 3. Systolic blood pressure (the "top number") declines from a little under 150 to a little over 147 with increases in temperature, UVA exposure, and UVB exposure. A decline of less than 3 mmHg may be statistically significant, but is it clinically or physiologically relevant? Maybe, maybe not. But there are other problems. First of all, seasonal variation in blood pressure have been known for decades, and have largely been attributed to temperature: warmth causes vasodilation while cold causes vasoconstriction. Obviously, solar UV radiation will go up along with temperature as winter turns to summer. Weller claims to show that UV exposure decreases systolic blood pressure in a manner independent of temperature, but if you read carefully you'll see that the patients' level of UV exposure is never actually measured, but rather estimated from a computer model run by the National Center for Atmospheric research. As the authors concede, "[s]ince it was not feasible to determine personal exposures to UV radiation and temperature, we approximated these exposures using environmental data retrieved from public databases at matched locations." My guess is that people with end-stage kidney failure probably don't get out as much as the rest of us, drawing the applicability of the data to the general population into question. The authors also state that ".[w]e analyzed systolic rather than diastolic BP as in dialysis patients the former is associated with patient outcomes." Yet the reference they cite clearly indicates that systolic blood pressure measurements taken in dialysis centers did NOT correlate with mortality. My last objection is that they claim that solar UV lowers blood pressure independently of temperature, while at the same time writing "[a]s expected, incident UV radiation and environmental temperature were closely associated." The complicated statistical gymnastics they use to tease out the separate effects of temperature and solar UV exposure seem suspect to me, although I concede I am no genius when it comes to statistics.
To be clear, Weller et al MAY be correct in stating that the UV radiation in sunlight, by itself and independently of temperature, causes a decrease in systolic blood pressure. I don't believe they're proven their caae, and at best the contribution of UV radiation to the overall seasonal variability in blood pressure, if it exists at all, is very small. My general reaction is "Meh."
https://www.ahajournals.org/doi/10.1161/JAHA.119.013837
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calgarymark
Forum Member
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 Posted - 05/27/2021 : 3:18:33 PM
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I couldn't find a suitable thread for this item; this one seemed the most suitable, if a naturist can use that term. This is mainly about the benefits of sunshine and Vitamin D.
Dr Roger Gillie was a British journalist who wrote extensively about the benefits of sunlight and Vitamin D. We know what that means for good health and a sense of well-being (as well as no tan lines). I just searched for Roger on DuckDuckGo (I refuse to use Google) and found an updated Wikipedia entry for him:
https://en.wikipedia.org/wiki/Oliver_Gillie
He died on 15 May 2021. Somebody updated the entry just a couple of days ago. The entry references an extensive obituary in the Guardian https://www.theguardian.com/society/2021/may/21/oliver-gillie-obituary
I crossed paths with Oliver at high school in the late 1950s and read many of his newspaper articles in the 1960s before I emigrated to Canada. I recommend that you study his paper ‘Sunlight Robbery’, which you can download at https://www.healthresearchforum.org.uk/oliver.html
RIP, Roger.
CalgaryMark
"Life's too short to be taken seriously".
"Be yourself - everyone else is taken". Attributed to Oscar Wilde.
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