Fertility at low and high altitude in Central Nepal

Since the 1930s, a number of different studies have tended to show that fertility is lower at high altitude. The present investigation attempts to provide some answers to this question by examining completed fertility rate (CFR) in Highland and Lowland villages in Central Nepal and relating rate differences to age at menarche, age at 1st childbirth, age at 1st marriage, incidence of venereal disease, birth control (vasectomy or hysterectomy), length of postpartum amenorrhea, and breastfeeding. Data was obtained by direct questioning, and under-reporting of births thus cannot be excluded. Fertility histories were taken from post-menopausal women over the age of 45 years. Results indicate no significant difference in reported menarcheal ages between highlanders and lowlanders. Age at 1st marriage and 1st childbirth were both significantly later in highlanders. CFR was significantly lower in highlanders. It would appear that the reduced fertility rate at high altitude can be partly attributable to later age at marriage and later 1st childbirth. Other factors, e.g., husband absenteeism and remarriage have also been suggested as possible contributors to the observed difference. This paper presents the results of a multiple regression analysis using 9 dependent variables: ages of marriage, 1st childbirth and menarch, the average gap between pregnancies, the average amount of time the husband was away, the number of marriages, presence or absence of venereal disease at some time, whether birth control was practiced and altitude status. Average pregnancy gap, age at 1st childbirth and presence or absence of venereal disease were the only variables that independently made a significcant contribution to CFR variance. The increase in pregnancy gap may be related to longer periods of breastfeeding in high altitude women and there would be a concomitant delay in recommencement of menstruation. In testing the hypothesis, no difference is found in reported duration of breastfeeding or in postpartum amenorrhea. The age at marriage and age at 1st childbirth accounted for over 16% of the explained variance in CFR. Some of the observed difference in CFR can be explained by the difference in marital age but not by the interval between marriage and 1st childbirth, as it was very similar in both groups. The lower CFR among the high altitude population could be due to lowering of biological fecundity at high altitude, or simply a matter of choice. The difference might reflect human reproductive hormone differences between high and low altitude populations. Further research will be needed to determine whether or not differences in CFR can be explained by variation in these factors.     

Electrocardiographic observations in high altitude residents of Nepal and Bolivia

Parameters computed from electrocardiographic recordings (mean frontal QRS axis, â QRS, positive (R-S) difference in lead V₁, incidence of atypical conduction pattern in V₁) were compared: (1) in two populations residing at the same altitude (3 800 m) but in different geographical sites: Aymaras in Bolivia and Tibetans in Nepal, (2) in three groups of Bolivians dwellers, ethnically similar and fully acclimatized, at three altitudes (4 780 m, 3 800 m, 400 m). This work involved 661 subjects. Results: (a) The mean â QRS value in highlanders is shifted to the right when compared to that of lowlanders: the right axis deviation increases with altitude, (b) The mean â QRS value is identical in Bolivian and Tibetan groups living at the same altitude, (c) The axis deviates to the left with aging in all the environmental conditions. This migration is accompanied by a lower incidence of positive (R-S) difference in adults compared to younger subjects, (d) The mean â QRS value of the females is always situated to the left of that males for all age groups. This difference receives a possible confirmation by the lower incidence of atypical complexes in V₁ in females, (e) The present values of â QRS as well as others found in the litterature and those of mean pulmonary arterial pressure reported by different authors have been plotted, both as a function of elevation: The two relationships can be described by two linear functions with a point of intersection. Such points suggest an altitude threshold above which a further decrease in barometric pressure results in marked cardiovascular responses. They are both located in the vicinity of 2 500 m.This work was supported by the Department of Cooperation Technique (Ministère des Affaires Etrangères) and the Centre National de la Recherche Scientifique (RCP. 253).     

Hemoglobin levels in high altitude Tibetan natives of northwest Nepal

Unusually low hemoglobin levels were found in a healthy population of Tibetan speaking people residing at 3800 m along the Nepal-Tibet frontier in northwest Nepal. Peoples native to the Tibetan plateau may have evolved novel adaptive strategies to hypoxic stress.     

Xerotolerant mycobiota from high altitude Anapurna soil, Nepal

Xerophilic and xerotolerant microfungi were isolated from soil samples collected in Anapurna Mountains, Nepal, at altitudes from 3000 to 5400 m. The total numbers and proportions of xerotolerant and psychrophilic strains in comparison with mesophilic mycobiota were determined by using different enumeration, selective media and four isolation methods. The most extreme xerophilic fungi were taxonomically identified as belonging to the genera Eurotium and Aspergillus. The low water activity of the soil due to dry climate and frequent binding of water in ice crystals favors a high proportion of xerotolerant fungal species. The correlation between xerotolerant and psychrophilic fungi was observed.     

Oxygen debt in submaximal and supramaximal exercise in children at high and low altitude

The effect of high altitude (HA) on O2 debt and blood lactate concentration [( L]) was examined in 10- to 13-yr-old children who exhibited the same level of physical fitness. Fifty-one children acclimatized to HA (3,700 m) were compared with 40 children living at low altitude (LA, 330 m) during submaximal (20-95% maximal aerobic power, MAP), maximal and supramaximal (115% MAP) bicycle exercise. Results showed that 1) maximal O2 uptake (VO2max) and maximal heart rate were significantly (P less than 0.001) lower at HA than at LA by 15% and 11 beats X min-1, respectively; 2) for a given absolute work load, O2 debt was higher at HA than at LA, and the slopes of the linear relationships between O2 debt and O2 uptake were significantly higher at HA; 3) when related to percent of VO2max, O2 debts in HA and LA were similar; for 115% MAP maximal O2 debt and [L] were not significantly different (maximal O2 debt, 45.7 +/- 2.7 and 45.9 +/- 3.8 ml X kg-1; [L], 6.0 +/- 0.3 and 6.7 +/- 0.5 mM); and 4) linear relationships between maximal O2 debt and [L] were the same at HA and LA. This suggests that HA did not modify the anaerobic capacity in children.     

Effects of exercise on young and adult cattle at low and high altitude

Nine calves and nine oxen walked on a treadmill in a climatized low pressure chamber for one hour each day, 2 weeks at 400 m and 4 weeks at 3,500 m. The overall effects of walking were: increases in heart rate, pulmonary arterial pressure, rectal temperature, respiratory rate, blood-pH and lactate/pyruvate ratio. Haemoglobin, haematocrit, blood specific gravity and blood viscosity increased in the oxen but decreased in the calves. Blood lactate and blood pyruvate declined in both age groups, plasma viscosity only in the calves. The exercise effects were more pronounced at 3,500 m than at 400 m as exemplified by the following percentile differences (3,500-400 m): in heart rate 26%, mean pulmonary arterial pressure: 22%, respiratory rate: 11%, blood pH: 0.3%, blood lactate: 39%, blood pyruvate: 56%, haemoglobin: 4%, blood viscosity: 5%. Compared with the calves, the oxen experienced larger increases in heart rate and respiratory rate in response to exercise, suggesting a greater rise in metabolic rate: they also showed a more pronounced respiratory alkalosis. Thus, exercise seems to have strained the oxen more than the calves. In the oxen, there was a training effect as judged by reductions in exercising heart rate, respiratory rate and rectal temperature.     

A case of high altitude cutaneous leishmaniasis in a non-endemic region in Nepal

A case of cutaneous leishmaniasis was discovered in a 32-year old man with a persistent erythematous plaque. The patient resides in a high altitude (~2000 m above sea level) area that is not endemic for cutaneous leishmaniasis in the Dunai village of Dolpa, Nepal. The patient's lesion was initially misdiagnosed as lupus vulgaris. After response failure to initial treatment, additional testing by histological microscopy revealed the presence of Leishmania amastigotes in tissue from the lesion, and the diagnosis of cutaneous leishmaniasis was confirmed by nested PCR DNA assay of tissue from the lesion, and by a positive rK39 test in blood. Sequencing of the kinetoplast region confirmed the presence of Leishmania donovani complex. The patient responded well to treatments for cutaneous leishmaniasis and the skin lesions regressed after 6 months. This is the first known case of cutaneous leishmaniasis in a patient in Nepal who resides at high altitude in a non-endemic region. Increasing temperatures in this region of Nepal may be expanding the range of vectors that transmit cutaneous leishmaniasis.     

The lung at high altitude

Men and mammals (excluding the indigenous mountain species) who are born at high altitude, or who ascend to live there for a long period, have to undergo acclimatization which affects virtually every system in the body. Since chronic hypoxia is the most important adverse factor in the mountain environment, the lung plays a major part in the process and shows many alterations in structure and function. However, we remain ignorant about many aspects of acclimatization of the lung to hypoxia especially at the ultrastructural level with respect to those cells whose normal function is not yet established. An account of what is known is given in this paper.     

Hepatic amoebiasis at high altitude

Latent amoebiasis is aggravated at high altitude. Protean manifestations are common. Fever is usually absent. Liver tenderness is not a feature and may have to be specially elicited. Leucocytosis is rare. Bowel symptoms inspite of presence of intestinal ulcerations are usually absent. Response to treatment with emetine or chloroquin is unsatisfactory and relapse rate is high. These points may interest mountaineers and other sojourners to high altitude.     

The athlete at high altitude

Track times at moderate altitudes (7000 to 8000 feet) are modified by decreased wind resistance and by systemic disturbances such as mountain sickness, disruption of training, and a decrease of maximum oxygen intake. The optimum period of acclimatization is probably two to three days. This permits adjustment of cerebrospinal fluid acid-base balance, but minimizes disturbances of plasma volume and stroke volume. Further study is needed to establish whether altitude training can improve performance in sea-level competitions.     

Nutritional alterations at high altitude in man

During the French 1980 Mount Pabil (7,102 m) Expedition, a study was made of four altitude-acclimatised climbers (age 36.5 +/- 3.6 years; VO2max 50.5 +/- 3.1 ml X kg-1). Intake of various nutrients, body weight, skinfold thicknesses as indices of body composition, and water and nitrogen balances, were recorded before, and during high altitude exposure, and again after the return to low altitude. There was a significant (35-57%) reduction in total caloric intake at high altitude. Body weight decreased progressively, mainly due to a reduction in body fat. The subjects apparently remained in water balance, while the nitrogen balance was always negative during high altitude exposure. The significant nutritional alterations were mainly observed above 6,000 m. They are discussed with respect to changes in feeding patterns and in hormonal status of the climbers accompanying hypoxia and other stressors proper to high altitude.     

Glucoregulatory hormones in man at high altitude

Concentrations of glucose, lactic acid, free fatty acid (FFA), insulin, cortisol and growth hormone (GH) in the blood were monitored in 15 euglycaemic men (sojourners, SJ) at sea level (SL) and while at altitudes of 3500 m and 5080 m, in acclimatised low landers (ALL) and in high altitude natives (HAN). In SJ, blood glucose and insulin concentrations showed a significant increase on the 3rd and 7th day after arrival at high altitude (HA), thereafter returning to sea level values and remaining the same during the entire period of their stay at 3500 m. Subsequently, on arrival at higher altitude (5080 m) the glucose concentrations again showed an increase over the preceding values and returned to SL values on day 41 while at 5080 m. A significant increase in cortisol concentrations was seen on day 3 after arrival at HA and the increased levels were maintained until day 21 at 3500 m. The cortisol concentrations on day 30 after arrival at 5080 m came down to SL values and remained unchanged thereafter. No appreciable change in GH and FFA was seen during the sojourn at HA. On the other hand, blood lactic acid concentration decreased significantly. There was no difference between the fasting glucose concentrations in ALL at 3500 m and in HAN at 3500 m and 4200 m compared to values of SJ at SL, whereas ALL at 4200 m had higher glucose values. Concentrations of plasma insulin and GH in ALL and HAN were higher than the values of SJ at SL, whereas cortisol values did not show any difference. These observations indicated that at HA the glucose values were high for the insulin concentration observed and might have been due to increased secretion of GH by the pituitary gland.     

Insulin secretion at high altitude in man

The effect of hypoxia on circulatory levels of insulin, its response to oral glucose administration (100 g) and changes in circadian rhythms of glucose as well as insulin were evaluated in euglycemic males at sea level (SL, 220 m) during their stay at high altitude (3500 m, SJ) and in high altitude natives (HAN).Basal glucose levels were not altered at high altitude but the rise in glucose ( glucose) after glucose load was significantly higher in SJ and HAN (p<0.01) as compared to SL values. An increase (p<0.01) both in basal as well as glucose induced rise in insulin secretion ( insulin) was observed at HA. The rise in insulin in SJ was significantly higher (p<0.01) than in HAN. This elevation in glucose and insulin levels was also evident at different times of the day. The circadian rhythmicity of glucose as well as insulin was altered by the altitude stress. The findings of the study show a rise in insulin level at HA but the hyperglycemia in the face of hyper-insulinism require the presumption of a simultaneous and dispropotionate rise of insulin antagonistic hormones upsetting the effect of insulin on glucose metabolism.Presented at International Conference of Biometeorology held at New Delhi from December 26–30, 1983.