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Diving and Hyperbaric Medicine Volume 37 No. 3 September 2007162
Abstract
The effect of ageing on risk for development of decompression illness in divers has often been reported as an incidental
nding in epidemiological analyses of diving accidents. No previous publications have specically attempted to quantify
or qualify those risks if present. This study demonstrates that ageing increases risk for injury overall, serious injury in
particular, and lessens recovery potential.
Age associated risks of recreational scuba diving
Richard W Smerz
Introduction
Ageing has long been believed to increase risk for developing
decompression illness in scuba divers. As many as 11 reports
have indicated that age represented a risk factor, while three
others have suggested otherwise.
1
In a previously published
study conducted at the Hyperbaric Treatment Center (HTC)
at the University of Hawaii’s John A Burns School of
Medicine, which had assessed the efcacy and outcomes
of the unique treatment tables employed there,
2
it had been
noted that older divers who had suffered signicant injury
seemed to have less favourable outcomes. As a result of
this incidental nding, there was an interest to investigate
the interaction of ageing and decompression illness to
determine whether there was an association between age and
susceptibility to decompression illness, as well as recovery
from decompression illness. This study attempted to more
fully elucidate age-related risks associated with scuba
diving accidents and to qualify their nature and quantify
their impact.
Methods
A chart review of 889 cases treated for decompression
illness (DCI) at the HTC between 1983 and 2003 was
undertaken in 2004. During a previous review, all cases had
been scored by a single investigator with a pre-treatment as
well as a post-treatment functional impairment score based
upon physical ndings and limitations to the conduct of
activities of daily living (ADL) at the time of presentation
and at the time of discharge respectively. This allowed for
assessment of improvement resulting from recompression
therapy. Cases were then grouped according to age decades:
20 years or less, 21–30, 31–40, 41–50, 51–60, and 61 and
above. The percentage of the study population represented
by each age group was determined. These data were then
compared with the same age groupings of injured divers
as reported by the Divers Alert Network (DAN) at Duke
University for the years 1987–2002 from their database. Both
of these data sets were compared to the average percentages
in each of the same age groups for all US divers certied by
the Professional Association of Diving Instructors (PADI)
for the period of time spanning that of the HTC study
cohort to determine whether there was any disproportionate
representation of injury in any age group. The percentage
of HTC cases which failed to achieve complete functional
recovery for each group was then determined to assess age-
related recovery potential. Finally, the percentage of HTC
cases in each age group who presented with serious/severe
injury was determined as well as the percentage of those
cases that were left with residuals.
Results
The number of HTC cases and their percentage of the
total population are depicted in Table 1. The percentage
of cases in the DAN database for years 1987–2002 for the
same age groups as the HTC study population were 3.3%,
21.7%, 35.7%, 23.3%, 8.7%, and 2.0% respectively. Table
2 compares both the HTC and DAN injury percentages to
the percentage of PADI-certied US divers in the same age
groups.
There were 250 HTC cases (28.1%) that were classied as
serious. Table 3 demonstrates the numbers and percentages
of serious HTC cases as well as the percentage that had
residuals in each age group.
Of the total number of cases classied as mild/moderate
severity, only 0.5% failed to achieve full functional
recovery.
Discussion
There are few published data in the literature that address
the age associated risks of scuba diving aside from those
done annually by the Divers Alert Network in the report on
recreational diving injuries and fatalities.
3
Several studies
Age group # HTC % HTC % with
(years) cases cases residuals
20 or less 47 5.2% 6.3%
21–30 293 31.8% 3.8%
31–40 318 35.8% 6.2%
41–50 156 17.5% 8.9%
51–60 60 6.7% 13.3%
61 or more 15 1.6% 33.3%
Table 1
Percentage HTC cases by age group (n = 889)
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Diving and Hyperbaric Medicine Volume 37 No. 3 September 2007 163
have intimated that age is a risk factor, but none have
attempted to quantify that risk. This study was undertaken
to determine whether such risk exists, attempt to develop a
“sense” of the magnitude of any age associated risk as well
as to dene at what age risks may become signicant.
A reasonable place to begin to tackle these questions was in
rst determining how many divers there are in each of the
selected age groupings. PADI has trained about 70% of US
recreational divers. Using their statistics,
4
the percentage
of the total population of PADI-certied divers in each of
this study’s age groups could be estimated. It would seem
logical that if this is the actual distribution of divers by
age group, that accidents randomly occurring to divers
might be similarly distributed. This would presume that all
certied divers are in fact actively diving consistent with
that distribution. That in fact may not and probably is not
the case. We need better denominator data such as the total
number of dives per diver in each age group before we can
more condently draw any rational conclusions as to the
true incidence of injury in any age group. However, it is not
unreasonable to conclude that any measure of injury rate
which exceeds the known proportion of divers in a particular
age group would be unexpected and highly suggestive for
signicance. Thus beginning at age 31 in both the HTC and
DAN data sets there is an injury rate distribution ranging
from 1.4 to 2.9 times greater than the age population
percentage of certied divers in which the injuries occurred.
Between ages 31 and 50 the range is 1.4 to 1.8 times greater
and between ages 51 and 61+, the range is 2.2 to 2.9 times
greater. This suggests that as divers age, their risk for injury
increases and becomes more pronounced after age 40 based
on this study (Table 2).
Data from Table 1 based upon the HTC cases shows that
with advancing age, an injured diver is at increasingly
greater risk for incomplete recovery and again this starts to
be more pronounced after age 40 and that risk signicantly
increases at age 50 and older. Fully one-third of those over
age 60 failed to achieve full functional recovery in the
HTC population. More ominous was the nding that as
one reached the age of 50, there was greater likelihood of
sustaining a serious injury along with a markedly increased
risk for incomplete recovery (Table 3).
Conclusions
This study clearly demonstrates that as divers age, there is
some increased risk for decompression illness. Furthermore,
it suggests that they are at greater risk for serious injury.
If injured there is greater risk for incomplete recovery,
and if seriously injured they are at substantial risk for
incomplete recovery. Consequently, older divers should
become increasingly conservative with their diving practices,
limiting depth and total dive times in order to reduce and
limit these risks.
References
Bove A. Diving medicine, 3rd ed. Philadelphia: Saunders
& Co; 1997. p. 156.
Smerz R, Overlock, R, Nakayama, H. Hawaiian
deep treatments, efcacy and outcomes, 1983–2003.
Undersea Hyperb Med. 2005; 32: 363-73.
Vann RD, Denoble PJ, Uguccioni DM, et al. Report
on decompression illness, diving fatalities, and project
dive exploration: DAN’s annual review of recreational
scuba diving injuries and fatalities based on 2003 data.
Durham: Divers Alert Network; 2004. p. 46-77.
PADI Americas. PADI diver statistics. Available
at <http://www.padi.com> Accessed 23 December
2005.
Richard W Smerz, DO, MTMH, Associate Clinical Professor
University of Hawaii, John A Burns School of Medicine, and
Medical Director, Hyperbaric Treatment Center
347 N Kuakini St, Honolulu, HI 96817, USA
E-mail: <rsmerz@htchawaii.com>
Key words
Decompression sickness, scuba accidents, risk factors, age,
DAN – Divers Alert Network, data, treatment sequelae
Reprinted with kind permission from Smerz RW. Age
associated risks of recreational scuba diving. Hawaii Med
J. 2006; 65 :140-1, 153.
1
2
3
4
Age group % HTC % DAN % PADI
(years) cases cases divers
20 or less 5.2 3.3 17.7
21–30 31.8 21.7 41.0
31–40 35.8 35.7 25.3
41–50 17.5 23.3 12.5
51–60 6.7 8.7 3.0
61 or more 1.6 2.0 0.7
Table 2
Percentage HTC and DAN cases vs. PADI–certied
divers by age group
Age group # HTC % serious % with
(years) serious cases cases residuals
20 or less 15 31.9% 20%
21–30 62 21.1% 19.3%
31–40 83 26% 21.6%
41–50 49 31.4% 30.6%
51–60 27 45% 29.6%
61 or more 9 60% 44%
Table 3
HTC serious cases and percentage with residuals by
age group
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