Who Gets Bent More?

During 1998 and 2002, Dan’s Project Dive Exploration tracked the incidence of decompression sickness (DCS) in four different recreational diving populations: live-aboards, shore/day boats, Cozumel dive guides, and Scapa Flow wreck divers (Britain’s Orkney Islands). Each group has certain inherent risks: Cozumel dive guides dive most frequently; shore/day boats attract more novice divers; live-aboards host gorilla divers who do multiple dives for seven to ten-day stretches; Scapa Flow wreck divers endure cold water and dive square profiles. Try hazarding a guess as to how these risk factors translate into actual bends rates for each different population; then compare your prediction to the actual rates shown in the table below.

For the study, 4,255 divers conducted 6,397 dive series (each series with between one and 88 dives) involving 41,294 air and 7,254 Nitrox dives. Out of these, there were 26 DCS cases (9 Type I, 17 Type II). The table below shows the DCS rate per 10,000 dives and the DCS rate per 100 divers.

As you can see from the table, live-aboard divers came out on the low end with one case of DCS per 10,000 dives (0.1%). Scapa Flow divers and Cozumel dive guides were on the high end in rates per 10,000 dives. While numerous variables affect the different dive groups studied, the results are interesting and should encourage more study as to the reasons for the wide variance.