Diabetes and Diving. The question DAN wants to explore is: How safe is it?

Reprinted from Alert Diver (Jan/Feb 1997) By Guy de Lisle Dear, M.B., FRCA, DAN Assistant Medical Director

Diabetes and Diving Get New Scrutiny The traditional view of diving physicians has been to ban individuals with diabetes from diving. Dive medical researchers discussed the topic of diving with diabetes at the May 1996 meeting of the Undersea and Hyperbaric Medical Society (UHMS). The work shop, "Some Diabetics Are Fit to Dive, But Who?" convened to discuss the issue. Researchers discussed the possibilities that the ban on divers with insulin-dependent diabetes mellitis (IDDM) may be too severe, noting that hypoglycemia while underwater or on the surface may be less common than previously believed.

The undisputed risk remains, however, that divers with diabetes who experience a hypoglycemic attack while underwater risk drowning. At the same time, they can endanger their buddies, since diving is a shared responsibility.

DAN statistics reported at the UHMS meeting showed that of 550 fatalities reported to DAN from 1989 to 1994, seven had diabetes mellitus, which may have contributed to their deaths. Eight of the 2,400 episodes of decompression illness reported were divers with diabetes. This is in line with the expected numbers in the general population.

In the DAN survey reported on in the January/February 1996 issue of Alert Diver ("The Diabetes Question," p. 21), 164 divers with diabetes completed the questionnaire, noting they had made hundreds of dives safely. The majority of those who responded (129 divers) were IDDM divers.

Dr. George Burghen, Chief of Endocrinology and Metabolism at the University of Tennessee, a committee member in the American Diabetes Association, has developed procedures and special training for divers with diabetes. He presented evidence that selected individuals with diabetes could be allowed to dive under specified conditions.

This view was endorsed by Dr. Chris Edge of the UK Sports Diving Medical Committee. In England, he notes, the diver with diabetes has the responsibility of running the training program for his respective club.

The selection of the diver with diabetes and the pre-dive, in-dive and post-dive procedures have been precisely defined by the UK Sports Diving Medical Committee. The committee has nearly 100 divers registered in its database that is designed to record any incidents that occur during or after the dive. The good news is that to date they have registered no incidents in divers with diabetes.
At the UHMS meeting, Dr. Michael Lerch, researcher with the Department of Diabetology, Protestant Hospital, Witten, Germany, presented data from seven IDDM divers. Blood glucose levels were measured before and after every dive, and in no case did the blood sugar levels rise or fall excessively. One factor he did find to be a problem was that dehydration was more noticeable in his diabetic group.

Challenges

The problem of diving with diabetes is threefold.

The effect of diving on blood sugar levels is not known with confidence. Although persons with diabetes may participate in strenuous sports above the water, little data have been gathered on the true incidence of hypoglycemia during scuba diving.

The procedures by which divers with diabetes can dive safely have not been defined.

The numbers of divers on whom appropriate observations have been made is insufficient to draw firm conclusions regarding the safety of diving for individuals with diabetes. Very small numbers of divers with diabetes have been studied in the field.

DAN's new field study in divers with insulin-dependent diabetes will log approximately 400 dives and record blood sugar levels before and after multiple dives during a multiday dive period. This should enable the study of a fairly wide selection of divers, and hopefully, some insight gained into the variation blood sugar levels in IDDM divers.

What exactly is diabetes?
Diabetes mellitus (DM) is a disorder of the endocrine system, manifested by one of two things:

1. an insufficient production of insulin, or

2. the resistance of the body's cells to the actions of insulin, despite normal.

Persons with DM often have excessively high blood glucose (BG), called hyperglycemia, or a very low BG, better known as hypoglycemia.

Diabetes mellitus itself has two major forms:

1. Insulin-dependent diabetes (IDDM) in which insulin must be given by injection to control blood sugar levels, and

2. Non-insulin-dependent diabetes, which may be controlled bydiet or by oral hypoglycemic medications.

Who gets diabetes?
IDDM may occur in any age group from childhood to adulthood. The prevalence of diabetes in the United States population has been estimated to range between 2 percent at age 20 to 17.7 percent at ages 65-74. These rates include undiagnosed diabetes as well as previously diagnosed diabetes.(Diabetes, 1987).

The main risk to the diver is the occurrence of hypoglycemia, or low blood sugar levels, which may manifest as confusion, sweating, rapid heartbeat, unconsciousness and even death. High blood sugar levels, or hyperglycemia, may also cause unconsciousness although this usually develops much more slowly than with hypoglycemia. Impaired consciousness underwater can lead to almost certain death. Although hypoglycemia occurs most commonly in IDDM, it can also occur in individuals taking oral hypoglycemic medications.

Although hypo- or hyperglycemia can occur daily, other problems can develop in diabetes over the long term, including:

retinopathy (alterations in visual acuity)

disorders of the kidneys

coronary artery disease

changes in the central nervous system including abnormal nervous conduction, and

atherosclerosis, causing poor circulation in the limbs.

UHMS Conclusions
The UHMS workshop did come up with some important conclusions by a consensus of the diving physicians present. These were summarized by Dr. David Elliott, diving physician and physiologist and civilian consultant to the Royal Navy:

- Divers with diabetes are at risk of sudden loss of consciousness. As divers, this carries the ultimate risk of drowning and implies additional risks for their healthy buddies. Individuals with diabetes, however well the diabetes is controlled, should not be passed as fit to dive without restriction

- Individuals with diabetes who meet certain criteria can dive provided they dive in accordance with detailed procedures, such as those of the U.K. Sports Diving Medical Committee.

- Divers with diabetes should be examined periodically for complications of their disorder that disqualify them on the grounds of additional risks.

- Hypoglycemia in deep dives could be wrongly perceived by a diver with diabetes as nitrogen narcosis.

- Many questions remain unanswered - additional data collection in the field is essential.

Sources
- Prevalence of diabetes and impaired glucose tolerance and plasma glucose levels in the U.S. Population age 20-74 years. Diabetes April 1987.

- Alert Diver. Jan-Feb. p.21-23, 1996.

- Edge C. The Diabetic Diver in Medical Assessment of Fitness to Dive. Proceedings from the International Conference at the Edinburgh Conference Center. Pressure 25(4 July/August) 1996.

- Lerch M. and U. Thurm: Beyond the Frontier-IDDM and Scuba Diving - a Field Study. Undersea and Hyperbaric Medicine 23:15, 1996.

- Winsett R. et al. Diving Safely with Diabetics. International Conference on Underwater Education. p. 231-236, 1992.