I searched the forums, but couldn't find any references to the following study (full text available in pdf http://dmnu-pet5.hcuge.ch/pdf/BJSM2004.pdf and html http://bjsm.bmjjournals.com/cgi/content/full/38/2/108)
Negative neurofunctional effects of frequency, depth and environment in recreational scuba diving: the Geneva "memory dive" study.
D O Slosman1, S de Ribaupierre1, C Chicherio1,2, C Ludwig1,2, M-L Montandon1, M Allaoua1, L Genton1,3, C Pichard3, A Grousset4, E Mayer5, J-M Annoni5 and A de Ribaupierre2
Objectives: To explore relationships between scuba diving activity, brain, and behaviour, and more specifically between global cerebral blood flow (CBF) or cognitive performance and total, annual, or last 6 months’ frequencies, for standard dives or dives performed below 40 m, in cold water or warm sea geographical environments.
Methods: A prospective cohort study was used to examine divers from diving clubs around Lac Léman and Geneva University Hospital. The subjects were 215 healthy recreational divers (diving with self-contained underwater breathing apparatus). Main outcome measures were: measurement of global CBF by 133Xe SPECT (single photon emission computed tomography); psychometric and neuropsychological tests to assess perceptual-motor abilities, spatial discrimination, attentional resources, executive functioning, and memory; evaluation of scuba diving activity by questionnaire focusing on number and maximum depth of dives and geographical site of the diving activity (cold water v warm water); and body composition analyses (BMI).
Results: (1) A negative influence of depth of dives on CBF and its combined effect with BMI and age was found. (2) A specific diving environment (more than 80% of dives in lakes) had a negative effect on CBF. (3) Depth and number of dives had a negative influence on cognitive performance (speed, flexibility and inhibition processing in attentional tasks). (4) A negative effect of a specific diving environment on cognitive performance (flexibility and inhibition components) was found.
Conclusions: Scuba diving may have long-term negative neurofunctional effects when performed in extreme conditions, namely cold water, with more than 100 dives per year, and maximal depth below 40 m.
From the Discussion:
To our knowledge, the present study represents the first attempt to study long-term neurological effects in recreational scuba divers in a large sample of over 200 subjects by using a wide range of psychometric tests and objective quantitative parameters of global cerebral blood flow. It leads us to conclude that, apart from standard recreational diving which remains safe when performed in warm seas and at depths above 40 m, the combination of depth (below 40 m) and cold water diving appears to be associated with long-term neurological effects in active divers. Therefore this type of scuba diving should no longer be considered recreational scuba diving, but more rather an "extreme sport", for which specific medical advice should be considered. However, the residual risk can be lowered with increased control measures and appropriate risk assessment. A longitudinal follow-up study will be conducted to confirm these observations and warn the fast growing recreational scuba diving community against risks associated with regular deep dives in cold water.
As this was not a longitudinal study, there's an obvious correlation/causation question, i.e. instead of concluding that deep, cold water makes you stupid, they could have concluded that smart people seek out warm and shallow water :05:. The authors do note they are planning a follow-up which should help answer this.
I posted this here because of of their hypothesis (more of a speculation really) that "Overall, for an identical dive profile, diving in cold water may result in an increased nitrogen saturation state. In addition, knowing that the temperature of exhaled air is decreased, one may hypothesize that the blood wash-out of nitrogen may be lowered and therefore the increased tissue residence time of nitrogen could be associated with an increased risk of tissue alteration by local development of microbubbles, particularly in very sensitive tissue such as cerebral tissue."
Alex
Negative neurofunctional effects of frequency, depth and environment in recreational scuba diving: the Geneva "memory dive" study.
D O Slosman1, S de Ribaupierre1, C Chicherio1,2, C Ludwig1,2, M-L Montandon1, M Allaoua1, L Genton1,3, C Pichard3, A Grousset4, E Mayer5, J-M Annoni5 and A de Ribaupierre2
Objectives: To explore relationships between scuba diving activity, brain, and behaviour, and more specifically between global cerebral blood flow (CBF) or cognitive performance and total, annual, or last 6 months’ frequencies, for standard dives or dives performed below 40 m, in cold water or warm sea geographical environments.
Methods: A prospective cohort study was used to examine divers from diving clubs around Lac Léman and Geneva University Hospital. The subjects were 215 healthy recreational divers (diving with self-contained underwater breathing apparatus). Main outcome measures were: measurement of global CBF by 133Xe SPECT (single photon emission computed tomography); psychometric and neuropsychological tests to assess perceptual-motor abilities, spatial discrimination, attentional resources, executive functioning, and memory; evaluation of scuba diving activity by questionnaire focusing on number and maximum depth of dives and geographical site of the diving activity (cold water v warm water); and body composition analyses (BMI).
Results: (1) A negative influence of depth of dives on CBF and its combined effect with BMI and age was found. (2) A specific diving environment (more than 80% of dives in lakes) had a negative effect on CBF. (3) Depth and number of dives had a negative influence on cognitive performance (speed, flexibility and inhibition processing in attentional tasks). (4) A negative effect of a specific diving environment on cognitive performance (flexibility and inhibition components) was found.
Conclusions: Scuba diving may have long-term negative neurofunctional effects when performed in extreme conditions, namely cold water, with more than 100 dives per year, and maximal depth below 40 m.
From the Discussion:
To our knowledge, the present study represents the first attempt to study long-term neurological effects in recreational scuba divers in a large sample of over 200 subjects by using a wide range of psychometric tests and objective quantitative parameters of global cerebral blood flow. It leads us to conclude that, apart from standard recreational diving which remains safe when performed in warm seas and at depths above 40 m, the combination of depth (below 40 m) and cold water diving appears to be associated with long-term neurological effects in active divers. Therefore this type of scuba diving should no longer be considered recreational scuba diving, but more rather an "extreme sport", for which specific medical advice should be considered. However, the residual risk can be lowered with increased control measures and appropriate risk assessment. A longitudinal follow-up study will be conducted to confirm these observations and warn the fast growing recreational scuba diving community against risks associated with regular deep dives in cold water.
As this was not a longitudinal study, there's an obvious correlation/causation question, i.e. instead of concluding that deep, cold water makes you stupid, they could have concluded that smart people seek out warm and shallow water :05:. The authors do note they are planning a follow-up which should help answer this.
I posted this here because of of their hypothesis (more of a speculation really) that "Overall, for an identical dive profile, diving in cold water may result in an increased nitrogen saturation state. In addition, knowing that the temperature of exhaled air is decreased, one may hypothesize that the blood wash-out of nitrogen may be lowered and therefore the increased tissue residence time of nitrogen could be associated with an increased risk of tissue alteration by local development of microbubbles, particularly in very sensitive tissue such as cerebral tissue."
Alex
