[Andreas Triantopoulos]

http://www.scuba-doc.com/LTE.htm



Conclusions
Negative effects of long-term deep diving include dysbaric osteonecrosis, decreased pulmonary function due to airway narrowing, hearing loss, and liver changes. There are studies that suggest neurologic effects of diving, but these studies have been criticized for flaws in design. Damaged cells similar to those found after exposure to ionizing radiation have been observed, but there are no controlled studies to verify that diving caused the cell damage. The severity of the effects and the point at which they manifest themselves in deep divers appears to be established. What remains unknown is the point at which these changes occur in sports divers and at what depths and times. Because no definitive scientific information is available, it can only be speculated that air bubbles will always travel to end organs, affecting them in some manner.

There have been reports of encephalopathy, impairment of cognitive function, and abnormal EEGs using this rationale as an explanation. However, the Divers Alert Network has stated: "The supposition of any damage to the brain rests on the occurrence of so called silent bubbles occurring in the blood or brain and spinal cord. That such bubbles do exist has been well demonstrated by Doppler technology in blood and tissue studies of animals' spinal cords. Whether or not, however, these silent bubbles are the cause of changes in the brain is unproved...Divers should not be unduly concerned about {the Lancet study}. More research is needed, but the world is filled with many divers who have been diving for over 40 years who show no unusual deterioration in their abilities which would affect their quality of life...
Certainly, [the study's] results should not be discounted. However, in the absence of neurological decompression illness, many other studies in which divers were compared with non-divers, have failed to demonstrate that diving causes long-term neurological impairment or any functional abnormalities."