Antarctic Medicine

During the early part of the long polar night Lieutenant Danco died. Except for the depression of this melancholy bereavement, the health of the members of the expedition was fairly good; but the 70 days of continued darkness weighed heavily upon us. —Frederick A. Cook, MD, 1900¹

With its long winters of unremitting darkness, cold, and isolation, Antarctica is perhaps the harshest sustained human environment on earth. It would have astonished Dr Cook, who accompanied the first winter expedition to Antarctica in 1898, to know that 100 years later 18 nations would be operating 37 winter stations in the Antarctic, south of the 60th parallel,² and that more than 10,000 tourists and adventure seekers would visit Antarctica in the austral summer.

The environment is no less challenging now than it was then, however, and Antarctica continues to provide a natural laboratory in human response to sustained physiological and emotional stress. The isolation, confinement, and reliance on technology make Antarctica the closest earth analogue for long-duration space flight, despite the inability to replicate space-specific effects such as weightlessness, radiation, and altered atmosphere. Symposia and volumes devoted to Antarctic human biology have shown the multidisciplinary and international nature of the research,^{3 - 5} which has revealed systematic changes in endocrine function, cardiovascular health, immunology, and psychological adaptation.

Antarctica is an international continent, and each nation conducting research there has developed health care programs in response to its particular needs. Factors include the degree of physical isolation, the ability to provide supplies and medical evacuation by ship or aircraft, and the number of medically trained staff. On tourist ships, medical services are traditionally provided for older passengers with age-related medical problems.⁶ Younger and more adventuresome visitors to the Antarctic require medical treatment for traumatic injuries.⁶

Health care and research have gained greatly from international collaboration, especially within the framework of the Scientific Committee on Antarctic Research, in which a working group on human biology and medicine has been active for 25 years. The sharing of data, experiences of equipment, pharmaceuticals, diagnostic dilemmas, and management of difficult cases between physicians of different national Antarctic programs is a continuing process, and standards have improved with experience. New nations establishing health care facilities for the first time in Antarctica are able to gain from the decades of collective experience of others.

Original surveys in the 1970s recorded on handwritten medical logs showed that trauma and accidents were the most common health events, with most being of a minor nature.^{7 - 8} The next most common category was symptoms and ill-defined diseases, such as headaches, dyspepsia, and insomnia. High rates of dental problems and skin diseases contrasted with low rates of diseases related to the environment (eg, cold injury, sunburn, snowblindness) and psychiatric problems. Diagnoses have included cutaneous herpes, tinea, amoebic dysentery, hepatitis, malaria, pneumonia, and gout.

A computerized register has laid the foundation for more accurate data collection.⁹ One study, in the period from 1988 to 1997 (1967 person-years of data), recorded 5103 illnesses and 3910 injuries and adverse reactions (Table 1).¹⁰ Another study has confirmed that cold-related injuries are uncommon in Antarctica, and most are associated with recreational activities such as skiing and snowmobile driving.¹¹ Neither temperature nor windchill was found to influence the severity of frostbite, but prior cold injury was associated with a higher risk of subsequent cold-related injury. Skiing injuries were significantly more likely to be nontrivial than work-related injuries or injuries of other causes.¹² No polar-specific disease has been found in Antarctica, and any condition may occur consistent with age and sex of individuals, a ruptured intracranial aneurysm¹³ and intestinal hemorrhage¹⁴ being among such cases.

Most nations have predeparture medical screening, and some have psychological or psychiatric assessment. Varying forms of telemedicine are now in use,¹⁵ and today many stations have Internet access. Predeparture training of physicians in surgery, anesthesiology, radiology, dentistry, laboratory techniques, and medical training of lay staff are required for stations that are completely isolated,¹⁶ while a lower level of skill is generally acceptable in locations that are accessible by sea or air (Figure 1). Some nations, such as Australia, require a prophylactic appendectomy for the wintering physician.

At Antarctic research stations, the physician's prime task generally is to provide health care. Beyond the demands of such a broad and remote practice, the isolation from colleagues, family, and friends adds to the challenge for the Antarctic physician. However, many physicians perform a research program as a spare-time occupation, and are thus in a unique position to integrate clinical and evidence-based observation of their colleagues, who participate as research subjects during the winter isolation. This close association between research and clinical practice is not often available to primary care physicians in less remote situations.

Recent research has found consistent alterations in thyroid-hormone economy among persons living for extended periods in Antarctica. After several winter months in Antarctica, subjects show baseline increases in thyroid-stimulating hormone, as well as release of higher levels of thyroid-stimulating hormone in response to a standard challenge with intravenous thyroid-releasing hormone.¹⁷ Although they do not exhibit an overall increase in the levels of circulating triiodothyronine and thyroxin, such subjects show a consistently more rapid production and clearance of triiodothyronine. Collectively, these changes in thyroid-axis kinetics are known as the polar T3 [triiodothyronine] syndrome.^{17 - 18} Similar alterations in the hypothalamic-pituitary-thyroid axis have been replicated under laboratory conditions of low-temperature stress¹⁹ and may represent a physiological adaptation to cold.²⁰

Decreased hydroxylation of vitamin D in Australian and French subjects has been associated with the near-complete absence of UV-B radiation during the Antarctic winter.^{21 - 22} These findings were replicated in a recent Japanese study,²³ which also demonstrated a significant increase in parathyroid hormone, but there was no evidence of decreased bone mass over a 12-month period. Other studies have found decreased levels of testosterone and pituitary hormones,²⁴ and possibly improved insulin sensitivity.²⁵ Although these findings are suggestive, the long-term endocrine effects of repeated exposure to the circumpolar environment are still unknown.

The sedentary indoor life during the Antarctic winter, increased caloric intake, and decreased physical activity are all important factors to those incarcerated in Antarctica, albeit voluntarily. Weight, lipid levels, and blood pressure (BP) all typically increase in wintering staff. However, because Antarctic personnel generally live and eat with their physician, counseling and intervention are possible much earlier than in general practice.

One study found that normotensive subjects had a significant increase in systolic BP and decrease in heart rate, which followed a 24-hour cycle despite the absence of circadian light cues.²⁶ A randomized study examined the modification of cardiovascular risk factors in subjects who were sedentary in the winter.²⁷ The addition of either 3 or 7 weekly sessions of moderate exercise (30 minutes of bicycling at 60%-70% of cardiovascular capacity) significantly lowered BP. During the summer, when the background level of activity was higher, BP without added exercise was similar to exercising levels in winter. There was no further decrease in BP with additional exercise.²⁸

Prolonged residence near the South Pole may result in systemic changes in immune function. Following initial observations of an enhanced, delayed reactivity to the Mycobacterium antigen purified protein derivative,²⁹ cell-mediated immunity was assessed over a year at Mawson on the Antarctic continent, and also at sub-Antarctic Macquarie Island. The Mawson group showed decreased cutaneous responses with significant anergy and hypoergy, while the response of the Macquarie Island group was similar to healthy populations in temperate zones.³⁰ A follow-up study found that the Macquarie Island subjects had levels of hypoergy (9%) comparable with healthy populations, but there was a 4-fold increase in the prevalence of hypoergy (36%) in the Antarctic continental groups.³¹

Other studies have found evidence of alterations in T-cell function, including depression of cell-mediated immunity responses and a 50% reduction of T-cell proliferation to phytohemagglutinin mitogen,³² as well as changes in cytokine levels. Subjects also showed increased herpesvirus shedding and expansion of polyclonal latent Epstein-Barr virus–infected B-cell populations.^{32 - 33} Although no specific pattern of disease was associated with these immune changes, the findings have important health implications should viral diseases occur in the confined environment of space travel.

Australian personnel participating in 6-person, 100-day, 3000-km Antarctic traverses cannot be evacuated in an emergency, and are probably the most geographically isolated humans on the planet. A collaborative research program³⁴ with the Psychology and Behavior Laboratory at Johnson Space Center studied individual adaptation and team function in this psychologically challenging environment. In general, these groups functioned well with few systematic effects. Most of the psychological difficulties appeared to occur within specific individuals or between individuals, and did not affect all members of the group equally. These results are similar to those found among groups from New Zealand,³⁵ Japan,³⁶ and the United States,³⁷ although these studies have found some evidence for a general syndrome of subclinical depression during the Antarctic winter.

In larger wintering groups, the primary sources of social dysfunction also seem related to individual personality factors, unique social interactions in each group, and local events, although the degree and length of isolation were also important.³³ The primary factors reported to have positive effects on staff were social events, a sense of accomplishment for difficult tasks, feelings of personal growth and introspection, and sense of community. Such results provide important data and insight on how humans adapt to the stress of extreme isolation, confinement, and the harsh environment of Antarctica, all of which will be critical to the success of long-duration human space travel.³⁸