The diving age range varies from 17 to 20 years at one extreme, to 35 at the other. In adulthood, age is of limited value in success prediction for achieving diving skills, but the most satisfactory age is in the early twenties.
Most professional diving schools prefer to select divers aged 22 to 29 years. Beyond this range the candidate will have a more limited life as a working diver, whereas under the age of 22 years they are usually not experienced enough in their basic work skills, and also perhaps are not as reliable or mature. Failure rates in training professional diving candi¬dates below the age of 19 years makes this practice commercially unprofitable.
The incidence of decompression sickness (DCS) (which is very relevant to deep or commercial diving) doubles in divers of 28 years, compared to those of 18 years. The incidence of death from cardiac disease is much greater after the age of 45-50 years, when it is second only to drowning as the cause of death. It has been shown that dysbaric osteonecrosis incidence is related to diving age (but this may also be due to greater hyperbaric exposure with age).
Beyond the age of 35 years, apart from an appreciable increase in susceptibility to some diving illnesses, there is a probable reluctance to persevere with adverse environmental and social conditions. There is also an increased incidence of general medical problems. In an Australian survey, the incidence of medical disorders causing failure to comply strictly with the Australian Standards for Professional Divers was 45 per cent in the over-thirty-fives (diving medical standards). This was compared to a 20 per cent incidence in the candidates in their twenties, and illustrates the high medical standards required (but not always achieved), as well as the adverse effects of diving age.
In recreational diving, there is no upper age limit. Especially with experienced divers, they can often modify their diving activities to take into account the limitations imposed by aging.
There is also a tendency for much older people, and especially those associated with yachting, to take up diving as part of their marine lifestyle. Thus we now have people commencing diving who have retired from their normal occupation, and although diving is often a valuable contribution to the quality of life of these people, this places an added burden on the medical examiner. There are still the same hazards as mentioned above, but because the diving activities can be tailored to the individual, greater tolerance can be allowed in recreational than professional diving. Nevertheless, recreational diving often does not have the same logistical support and safety procedures that are employed by professionals.
With increasing diving age, there is increasing infirmity and the increased use of medications, both of which can reduce diving safety. Of special note is the prevalence of:
• arthritis and musculoskeletal disorders;
• cardiovascular disorders
• cerebrovascular disease and dementias;
• ocular problems; and
The reduction in physical fitness, involving both cardiac and respiratory function as well as muscular strength, is likely to restrict considerably the environmental demands that can be met safely. Reduced physiological reserves attributed to aging may also be related to genetically determined disorders or disuse. Preconceived attitudes may reduce the expectations of performance, leading to disuse.
Maximum oxygen consumption reduces approximately 1 per cent per year of life. In sedentary individuals, the decline is greater in early adulthood and the curve is less steep in later life, but with regular exercise this decline can be halved. The decline is due to both cardiorespiratory and musculoskeletal factors.
Swimming without fins, at a speed of about 30 metres per minute (a 1-knot current speed), requires a metabolic equivalent unit (MET) of 10.0. (One MET unit is defined as consumption of 3.5 ml Q/kg body weight per minute.)
There is an increase in arterial stiffness with aging, leading to an increase in blood pressure and left ventricular hypertrophy. The exercise-induced rise in heart rate declines by 3.2 per cent per decade of life.
There is a decrease in elasticity of the lung parenchyma, and increase in fibrous tissue and increased resistance to airflow, with age. The vital capacity reduces by 30-50 per cent, and there is an increase of residual volume by 40-50 per cent, by the age of 70 years. This produces breathlessness at lesser work loads.
Maximum strength is achieved by the third decade, levels off until about the age of 60 years and then declines by 10-15 per cent per decade.
Listing the physiological decrements associated with age ignores the considerable individual variation, and so our assessment must be performance based in each case.
If the aged diver is able to continue to achieve a standard of physical fitness commensurate with diving safety, then the multiple theoretical and practical decrements should not be held against him. Thus, irrespective of age, the diver (either trainee or experienced) should still be able to perform a 1-km swim in less than 30 minutes, or a 200-metre swim in less than 5 minutes, unaided by equipment. If the diver, aged or otherwise, is unable to achieve such a basic standard of physical fitness and aquatic skill, then much diving activity would be unacceptably hazardous.
Certain diving illnesses are more likely to develop with age. The most important of these is cardiac disease, which is now probably the most common genuine cause of death in recreational diving (drowning only reflects the medium in which the accident occurs). The strenuous exercise required to swim against tidal currents and to rescue other divers, is such that a subclinical obstruction to a coronary artery (80 per cent or greater) is likely to be converted into a clinical case report of the sudden death syndrome.
Although physiological diving age is more important than chronological age, for divers aged over 40 years it is recommended that regular re-examinations be carried out in order to detect medical abnormalities which may interfere with efficiency and safety in the diving environment. Electrocardiographic examinations during maximal exercise may be recommended as part of each five-year medical, after this age, especially if cardiac risk factors are present.
DCS is also far more common with increasing age, and becomes a considerable handicap beyond the age of 40 years. With increasing age, a more conservative allowance must be made - restricting the decompression schedules. These authors arbitrarily recommend that older divers reduce their allowable bottom time by 10 per cent for each decade after the age of 30 years.
One of the commonest problems with the aging diver, is presbyopia. This interferes with the diver reading his meters, gauges and camera settings. It can be overcome by the use of a convex lens, stuck onto the lower rim of the face mask.
Increased sensitivity to cold can be partly countered by limiting diving to warmer waters, or by the use of thermal protection clothing.
There are suggestions that repetitive and excessive diving may produce some form of cerebral impairment which increase the effects of aging, but there is little evidence to support such a concept. Indeed, the anecdotal evidence for such a situation is countered by similar anecdotal evidence implying that old divers are an exciting, innovative and socially active group.
There are positive aspects to age, including the accumulated knowledge both of diving and other related activities, more prudence and care in dive planning and the choice of diving sites, and possibly more mature judgement. The aged diver is less likely to be swayed by social, peer, financial or ego pressures.
Many divers have continued diving into their eighties, and the social value of diving should not be underestimated. In Australia, there is even a Sub- Aquatic Geriatric Association (SAGA), to which this author has received (junior) honorary membership.