Acclimatization in Human Beings

the process of active adjustment (adaptation) of the organism to new climatic conditions.

Acclimatization occurs when the usual level of mobile equilibrium between an organism and the external environment under a particular climate over a prolonged period of time is altered and gradually, after a certain interval, a more or less stable equilibrium is established. The process of acclimatization is regulated by reflex and neurohumoral paths. The physical and geographical environment acts upon the human organism by means of a complex combination of meteorological factors whose continual interactions are reflected in changes in the weather. A change of climate frequently has a stimulating effect on the organism and can be employed in strengthening the body and in the treatment of various illnesses. This is the reason for sending patients to health resorts. The climate of the northern plains and mountains has the most invigorating effect on healthy people. Living conditions, work and rest conditions—housing, place of work, clothing, and diet—and special hygienic adaptations such as airconditioning and masks are also important factors.

Weak and sick people, who are especially sensitive to change of climate, may experience a derangement. Their physiological adaptive mechanism breaks down; various indispositions (sluggishness, lassitude, and headaches) and nervous and cardiovascular disorders occur. Chronic diseases—high blood pressure, stenocardia, tuberculosis, and rheumatism—can become aggravated. To ensure normal adaptation it is very important to examine a patient for any diseases which would make his moving to a particular climate inadvisable. Acclimatization to extreme conditions (that is, the north, hot climates, and mountain climates) places the greatest strain on the adaptive mechanisms.

Northern climates. In medical terms, the arctic and subarctic climates are extremely uncomfortable for man because of the acute insufficiency of ultraviolet radiation (sunlight deprivation) and the presence of polar light, magnetic disturbances, magnetic storms, and so on. Nevertheless, most people become acclimatized after one or two years, and, in rare cases, after three years. Hard work speeds up this process. However, unusually susceptible people may show a decline in health. This decline can be prevented by a suitable diet, the taking of vitamins, and strengthening the body by physical exercise.

Hot climates. Upon moving to a hot climate, where the air temperature is higher than body temperature, there is an increase in the rates of metabolism, respiration, circulation of the blood, and so on, accompanied by a lowering of the capacity to work; this is related to the difficulty of heat emission. If the air is dry, a person can endure even very high temperatures. (The upper limit on adaptation under optimal low relative humidity is held to be 40°C.) However, as the humidity in the air increases, the strain on a person’s adaptive mechanisms also increases. The most difficult adaptation is to the climate of humid, tropical forests, where the heat and very high humidity are combined with a total lack of wind. (The upper limit on adaptation when the relative humidity is 85 percent is considered to be 30°-31°C.) Overheating of the body can lead to heat stroke, heat exhaustion, and, in cases of excessive loss of mineral salts through perspiration, to heat cramps. Relief can be obtained with airconditioning, a sensible diet, adequate water-salt intake, suitable clothing, and so on.

Mountain climates. Mountain climate is characterized by lower atmospheric pressure, more intense solar radiation, increased ionization, and low air temperature. A decrease in the partial pressure of oxygen in the alveolar ducts causes an increase in the ventilation of the lungs and an increase in heart rate; irritation of the blood-producing apparatus leads to an increase in the number of erythrocytes and in the hemoglobin content of the blood. At extreme heights mountain sickness often appears. Ascents are especially difficult for elderly people. Health and the capacity to work improve if the ascent is made in more or less gradual stages (from several days to several weeks). Acclimatization usually takes place within seven to 12 days.