Evaluation of cognitive performance in professional divers by means of event-related potentials and neuropsychology

Persistent neuroinflammation and functional deficits in a murine model of decompression sickness

We hypothesized that early intra-central nervous system (CNS) responses in a murine model of decompression sickness (DCS) would be reflected by changes in the microparticles (MPs) that exit the brain via the glymphatic system, and due to systemic responses the MPs would cause inflammatory changes lasting for many days leading to functional neurological deficits. Elevations on the order of threefold of blood-borne inflammatory MPs, neutrophil activation, glymphatic flow, and neuroinflammation in cerebral cortex and hippocampus were found in mice at 12 days after exposure to 760 kPa of air for 2 h. Mice also exhibited a significant decline in memory and locomotor activity, as assessed by novel object recognition and rotarod testing. Similar inflammatory changes in blood, neuroinflammation, and functional impairments were initiated in naïve mice by injection of filamentous (F-) actin-positive MPs, but not F-actin-negative MPs, obtained from decompressed mice. We conclude that high pressure/decompression stress establishes a systemic inflammatory process that results in prolonged neuroinflammation and functional impairments in the mouse decompression model.NEW & NOTEWORTHY Elevated glymphatic flow due to astrocyte and microglial activation from high-pressure exposure triggers release of microparticles (MPs) to the circulation where neutrophil activation and production of filamentous (F)-actin expressing MPs result in a persistent feed-forward neuroinflammatory cycle and functional deficits lasting for at least 12 days.

Cognitive Functions in Scuba, Technical and Saturation Diving

Scuba diving as a recreational activity is becoming increasingly popular. However, the safety of this activity, especially in the out-of-comfort zone, has been discussed worldwide. The latest publications bring conclusions regarding negative effects on cognitive functions. We compare the acute and chronic effects of diving on cognitive functioning depending on the type of dive performed, including recreational, technical and saturation diving. However, the results of research show that acute and chronic effects on cognitive functions can be negative. While acute effects are reversible after the ascent, chronic effects include white matter lesions in magnetic resonance imaging scans. We believe that more investigations should be performed to determine the chronic effects that could be observed after a few months of observations in a group of regular, intense divers. In addition, publications referring to technical divers are very limited, which is disquieting, as this particular group of divers seems to be neglected in research concerning the effects of diving on cognitive functions.

Cognition impairment of rat in undersea environment

This study was designed to examine the cognitive responses of rat simulation model of the undersea environment. Rats were randomized into five groups: control, restraint, hyperbaric air, restraint with hyperbaric air, and restraint with hyperbaric air and immersion The cognition functions were assessed by Morris water maze test and forced swimming test. The cerebral blood flow (CBF) was monitored. The parameters examined were total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-px), glutathione (GSH), glutathione reductase (GR), and malondialdehyde (MDA). It was observed that the rats in the experimental groups had impaired learning and memory and behavioral despair accompanied by increase in CBF and MDA levels but decrease of TAC, SOD, CAT, GSH-px, GSH, and GR levels. These indicated that the simulated underwater conditions might cause immediate and transient cognition impairment in the rat models. The simulated environment induced oxidative stress led to the negative cognitive changes.

Protein tau concentration in blood increases after SCUBA diving: an observational study

Purpose

It is speculated that diving might be harmful to the nervous system. The aim of this study was to determine if established markers of neuronal injury were increased in the blood after diving.

Methods

Thirty-two divers performed two identical dives, 48 h apart, in a water-filled hyperbaric chamber pressurized to an equivalent of 42 m of sea water for 10 min. After one of the two dives, normobaric oxygen was breathed for 30 min, with air breathed after the other. Blood samples were obtained before and at 30–45 and 120 min after diving. Concentrations of glial fibrillary acidic, neurofilament light, and tau proteins were measured using single molecule array technology. Doppler ultrasound was used to detect venous gas emboli.

Results

Tau was significantly increased at 30–45 min after the second dive (p < 0.0098) and at 120 min after both dives (p < 0.0008/p < 0.0041). Comparison of matching samples showed that oxygen breathing after diving did not influence tau results. There was no correlation between tau concentrations and the presence of venous gas emboli. Glial fibrillary acidic protein was decreased 30–45 min after the first dive but at no other point. Neurofilament light concentrations did not change.

Conclusions

Tau seems to be a promising marker of dive-related neuronal stress, which is independent of the presence of venous gas emboli. Future studies could validate these results and determine if there is a quantitative relationship between dive exposure and change in tau blood concentration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-022-04892-9.

The practice of speleology: What is its relationship with spatial abilities?

Given the evidence of motor and exploring activities being related to spatial abilities on different scales, the present study considers the case of speleology, a peculiar underground exploratory activity. The relation of this practice with spatial abilities was examined. The study compares a group of expert speleologists (18), a group with a reduced amount of experience in speleology (19 novice speleologists), and a group with a similar amount of practice but in the outdoors (19 experts mountaineers). Group differences will be investigated in terms of (i) small-scale spatial task performance (rotation-based and spatial working memory); (ii) large-scale environment learning (reproduced using verbal descriptions) asking participants to learn a path through a cave or up a mountain (in a counterbalanced order) and then to test their recall with true/false spatial questions and graphical representation tasks; and (iii) self-reports of wayfinding attitudes. The results of linear models showed that, after controlling for age, gender, years of education, and vocabulary scores, expert speleologists had greater mental rotation and perspective-taking abilities and less spatial anxiety than expert mountaineers, and the former performed the true/false questions better than the latter. It should be noted that participants who reported having guiding/path-finding experiences had greater accuracy in graphical representation performance and higher scores in attitude towards orientation. Overall, expertise in speleology is related to spatial abilities on different scales and might have a distinctive role in comparison with other motor practices, pointing to the potential value of examining speleology in the spatial cognition framework.

Effect of Long-Term Diving Exposure on Sleep of Male Occupational Divers in Southern Taiwan: A Cross-Sectional Study

OBJECTIVE

Divers with a history of decompression sickness may be at high risk for sleep problems. However, limited studies have investigated the relationship between diving exposure and sleep problems of occupational divers. This study investigated the association between diving exposure and sleep quality and quantity among male occupational divers in southern Taiwan.

METHODS

This descriptive, cross-sectional study included 52 occupational divers and 121 non-divers recruited from southern Taiwan in 2018. Survey data were collected using the Taiwanese version of the Hospital Anxiety and Depression Scale, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and a self-report questionnaire that included demographic variables, diving exposure/protocols, and factors associated with sleep quality.

RESULTS

Among all participants examined, occupational divers were significantly more likely to have both poor sleep quality (adjusted odds ratio [OR] = 3.00; 95% confidence interval [CI] = 1.48-6.06; P = 0.002) and excessive daytime sleepiness (adjusted OR = 4.49; 95% CI = 2.12-9.52; P < 0.001). The diving exposure time, depth, ascent rate, and decompression table use showed no significant associations between poor and good sleepers in the divers group. However, a history of decompression sickness was associated with poor sleep quality among divers (adjusted OR = 2.20; 95% CI = 1.07-4.54; P = 0.032).

CONCLUSIONS

Our results showed that occupational divers had poor sleep quality and more excessive sleepiness than non-divers. Decompression sickness likely contributes to poor sleep quality. Prevention and early detection of decompression sickness-related sleep problems should be an occupational health priority.

Effects of Hyperbaric Nitrogen Narcosis on Cognitive Performance in Recreational air SCUBA Divers: An Auditory Event-related Brain Potentials Study

BACKGROUND

The narcotic effect of hyperbaric nitrogen is most pronounced in air-breathing divers because it impairs diver's cognitive and behavioral performance, and limits the depth of dive profiles. We aimed to investigate the cognitive effects of simulated (500 kPa) air environments in recreational SCUBA divers, revealed by auditory event-related potentials (AERPs).

METHODS

A total of 18 healthy volunteer recreational air SCUBA divers participated in the study. AERPs were recorded in pre-dive, deep-dive, and post-dive sessions.

RESULTS

False-positive score variables were found with significantly higher differences and longer reaction times of hits during deep-dive and post-dive than pre-dive sessions. Also, P3 amplitudes were significantly reduced and peak latencies were prolonged during both deep-dive and post-dive compared with pre-dive sessions.

CONCLUSION

We observed that nitrogen narcosis at 500 kPa pressure in the dry hyperbaric chamber has a mild-to-moderate negative effect on the cognitive performance of recreational air SCUBA divers, which threatened the safety of diving. Although relatively decreased, this effect also continued in the post-dive sessions. These negative effects are especially important for divers engaged in open-sea diving. Our results show crucial implications for the kinds of control measures that can help to prevent nitrogen narcosis and diving accidents at depths up to 40 msw.

Executive Function among Chilean Shellfish Divers: A Cross-Sectional Study Considering Working and Health Conditions in Artisanal Fishing

Knowledge about professional diving-related risk factors for reduced executive function is limited. We therefore evaluated the association between decompression illness and executive functioning among artisanal divers in southern Chile. The cross-sectional study included 104 male divers and 58 male non-diving fishermen from two fishing communities. Divers self-reported frequency and severity of symptoms of decompression illness. Executive function was evaluated by perseverative responses and perseverative errors in the Wisconsin Card Sorting Test. Age, alcohol consumption, and symptoms of depression were a-priori defined as potential confounders and included in linear regression models. Comparing divers and non-divers, no differences in the executive function were found. Among divers, 75% reported a history of at least mild decompression sickness. Higher frequency and severity of symptoms of decompression illness were associated with reduced executive function. Therefore, intervention strategies for artisanal divers should focus on prevention of decompression illness.

Cognitive Deficits and White Matter Alterations in Highly Trained Scuba Divers

Nitrogen gas (N2), present in the normal atmospheric air, is a potential source of risk for scuba divers. It seems probable that myelin can represent, in hyperbaric conditions, a preferential site for the accumulation of N2 in central nervous system (CNS). The purpose of this study is to verify whether the practice of the scuba diving is capable to determine a damage of the brain white matter (WM) in a dose dependent manner and, consequently, possible deficiency of their cognitive abilities. For this purpose, 54 professional scuba divers (35 men and 19 women), with at least 2,000 dives in their careers, were studied. Possible alterations of brain WM were evaluated in terms of Fractional anisotropy (FA) by using Diffusion Tensor Imaging, whereas possible cognitive impairments were verified by means of neuropsychological testing, by studying: (1) General mental capability (2) Executive functioning; (3) Visuospatial construction such as Rey Complex Figure; (4) Attention and orientation: (5) Selective attention capacity and processing speed ability; (6) Memory. The results showed alteration of the WM in terms of changes in FA; these alterations, statistically significant but quantitatively quite modest, were mainly observed in the WM of the anterior part of the brain, whereas no differences were observed between left and right hemisphere. The alterations of the WM were associated with changes, also in this case statistically significant but quantitatively quite modest, of the cognitive functions, in particular of those dependent on the prefrontal cortex, such as attention and memory function. The present study leads to the conclusion that repeated dives, even performed in compliance with the current decompression tables, can progressively lead in the CNS to the formation of micro-lesions in the myelin sheet capable of altering the functioning of the neuron.