Long-term neurological effects of diving - revisited

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Michael_J

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Hi all,

I realize this topic has come up several times before, but I believe it's been several years since the last discussion and I wanted to revisit this in light of some recent literature that has come out including the below:
Curious if anyone who follows this space has any updated thoughts or assessments on risk profile and mitigation strategies. I would also be interested in how people are viewing the nitrox vs. air trade-off given some recent publications such as the below:
MJ
 
Hi all,

I realize this topic has come up several times before, but I believe it's been several years since the last discussion and I wanted to revisit this in light of some recent literature that has come out including the below:
Curious if anyone who follows this space has any updated thoughts or assessments on risk profile and mitigation strategies. I would also be interested in how people are viewing the nitrox vs. air trade-off given some recent publications such as the below:
MJ

MJ...

There's lots of things in life that negatively impact our mental health...you only have to turn on the morning news to reap the carnage...

Deteriorating mental health caused by scuba diving is the least of our worries...

I think some of our world leaders have mental health issues...and I don't know any of them that dive...I think a little NITROX would do them all a world of good...

W...
 
How do you resolve this paradox?

"Diving by itself seems to cause some decrease of short-term memory and higher cognitive function, including visual-motor skills; this resembles some of the effects of nitrogen narcosis and we suggest that this may be a prolonged effect of diving."

"There appeared to be no correlation between the diving experience (number of dives, years of diving) and the neuro-psychometric performance (Spearman correlations all p > 0.5)."

Junk Science.
 
I discovered a PFO through a couple of Neuro bends in the 90s it's closed but I have sections of memory loss from the time I started deep air and accelerated decompression.

It's difficult to know from these articles how it would translate to the indv because gases, schedules, ascent rated etc will/may be different.

As with most pursuits or lifestyle choices there will be ramifications from most forms of diving.

I now tend to only deco dive if it's worth it and avoid the weekly deep exposures in quarries over the winter that we're a feature of my diving in the 90s, favouring mines at shallow depths instead or NDL multi level quarry dives staying ahead of the curve, saving the deep stuff for wrecks.
 
This is an area that is still under investigation and is pretty complex. It stands to reason that "silent" venous gas emboli that become arterialized could cause small areas of infarction with effects being cumulative, but that has not been clearly demonstrated in the literature.

The first study (Balestra & Germonpre) you linked didn't find any correlation with PFO and the number and size of "Unidentified Bright Objects" (UBOs) found on MRI scans of diving subjects' brains, though PFO is not the only source of bubble shunting. They did find some evidence of performance decrements in divers vs control on a couple of the neuropsych tests, which would be correlated with the presence of those UBOs, but there's no demonstration of causality.

The Seyithonoglu et al. study looked at 11 divers, two of whom were saturation divers. Diffusion-weighted MRI is outside my wheelhouse so I'm not comfortable offering an in-depth critique of this study, though their statement, "These findings demonstrated the high sensitivity to hypoxia in the hippocampus, globus pallidus, and putamen[11]..." seems to indicate that they believe the changes in divers were related to hypoxia and I don't think they demonstrate this in their paper.

The Connolly & Lee meta-analysis reinforces the idea of white matter injury in divers vs controls.

The Hemelryck et al. group only did neuropsych testing, no imaging, but they had the largest "n" of the studies you linked. Their conclusion, "While it" *may* (emphasis mine) "be concluded that accident‐free SCUBA diving may have some long‐term adverse effects on short‐term memory, there is however, no evidence of general higher cognitive function deficiency..." is a good summary of what they found. I thought that the comparison with boxers (in whom chronic traumatic encephalopathy has been clearly demonstrated) was an interesting one. If there is a cumulative effect of diving on neurological functioning, it's much more subtle than CTE, but I think we're beginning to recognize that that the effect is probably there in at least some divers. It will be interesting to see research in this area evolve.

The Marinovic et al. study looked at vascular function in air divers, nitrox divers and controls. They looked at vascular "stiffness" after diving with two measurements: pulse wave velocity (PWV, higher velocity = more stiffness) and augmentation index (AI, higher AI = more stiffness). They found that PWV was higher in divers, but AI was lower, which they postulated was because of exercise while diving. I didn't see in the article where this was clearly elucidated, but these effects are transient. Higher inspired partial pressures of O2 result in vasoconstriction because the reactive oxygen species (free radicals) essentially scavenge circulating nitric oxide (NO), which is an endogenous vasodilator. The way I read the paper, the authors are wondering whether this could lead to effects similar to chronic hypertension in people who dive nitrox regularly. This has not been studied at all, and I think that the positive effects of nitrox far outweigh any of the theoretical negative effects, so I would not let this dissuade me from using nitrox to improve decompression efficiency and increase safety.

Tagging @Dr Simon Mitchell for his take on this.

Best regards,
DDM
 
How do you resolve this paradox?

"Diving by itself seems to cause some decrease of short-term memory and higher cognitive function, including visual-motor skills; this resembles some of the effects of nitrogen narcosis and we suggest that this may be a prolonged effect of diving."

"There appeared to be no correlation between the diving experience (number of dives, years of diving) and the neuro-psychometric performance (Spearman correlations all p > 0.5)."

Junk Science.

Not junk science, academic honesty IMO, and letting the reader conclude what he/she may from the two statements.

Best regards,
DDM
 
Not junk science, academic honesty IMO, and letting the reader conclude what he/she may from the two statements.

Best regards,
DDM

Academic honesty? Not what they taught me in grad school. Maybe the scientific method and intelectual honesty has been modified in the many years since. But I was taught that any hint paradox indicates your hypotheses (note - not theory) is incorrect and you are certainly missing something. There is far more than a hint of paradox here.

To flagrantly state that this may be a prolonged risk of diving when there is absolutely no evidence other than your own bias, no indication that number of dives or years diving have any effect is just bushwah. So definitely, yes - junk science. Or "alternate facts" as seems to be the current trend.
 
no indication that number of dives or years diving have any effect
Not a compelling argument. A single unfortunate incident is all it takes.....you seem to be assuming a slow build-up of effects until you reach a tipping point.....which is YOUR hypothesis.
 
https://www.shearwater.com/products/perdix-ai/

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