| ObjectiveHigh altitude is one of the most important parts of our country. Additionally, there has been an obvious increasing in the number of people who ascent to high altitude in our modern society. Therefore, the prevention of acute mountain sickness(AMS) is especially important. The present study aimed to explore the effect of different ascent profile on the prevalence of AMS, as well as the effect of the age, subjective sleep quality, and radiofrequency electromagnetic field(RF-EMF) exposure on the prevalence of AMS. By analyzing the subjects’ demographic characteristics, physiological parameters including heart rate(HR), blood pressure(BP), pulse oxygen saturation(Sp O2), hemoglobin(Hb), subjective sleep quality before and after altitude exposure, and the ascent profile, we expect to find out some risk factors for AMS and explore whether or not oxidative stress is a contributor to this phenomenon, providing novel avenues for the prevention and study of AMS.Methods1. The effect of ascent profile on the prevalence of AMSTwo cohorts were recruited. One cohort ascended from 500 m to 3,700 m by air, the other cohort ascended from 400 m to 3,900 m by car within six days. The HR and Sp O2 were measured. AMS was assessed using the Lake Louise scoring system(LLSS).2. The relationship between age and AMS at acute altitude exposureData from 1,000 young adult men was collected before ascent, which included the demographic characteristics, HR, BP, Sp O2, and the subjective sleep quality of the subjects. In the next morning after rapid ascent to 3,700 m, the abovementioned parameters were obtained again. Moreover, AMS of the subjects were assessed. The subjects were divided into 18-20, 21-25 26-30, and 31-35 years old groups. The abovementioned parameters of these groups were compared between groups. Logistic regression analysis was used to analyze the risk factors for AMS.3. Sleep changes in insomniacs and non-insomniacs at acute altitude exposure and its relation with AMSIn this work, 600 young Chinese men were enrolled. Subjects’ sleep quality was assessed using the Athens Insomnia Scale(AIS) prior to and after exposed to altitude. Additionally, AMS of the subjects were assessed. HR, BP, and Sp O2 were measured.4. Research in the prevalence of AMS of the subjects previously exposed to the RF-EMF at acute altitude exposure200 young Chinese male adults previously exposed to the RF-EMF were recruited. The controlled subjects were matched in terms of the age, race, education, body mass index(BMI), smoking and drinking habits, job seniority, and work shift of the RF-EMF exposed subjects. RF-EMF exposure was measured. Before ascent, at 500 m, baseline data including demographic characteristics, HR, BP, Sp O2, Hb, and the subjective sleep quality of the subjects was collected. In the next morning after rapid ascent to 3,700 m, the procedures were repeated. Additionally, AMS of the subjects were assessed. After a one-week stay at 3,700 m, the subjects further ascended to 4,400 m within 3 hours by car. In the next morning at 4,400 m, the abovementioned data was collected again. Logistic regression analysis was adopted to assess the risk factors for AMS.5. One possible mechanism for AMS: oxidative stressAdditionally, in the abovementioned study, plasma levels of superoxide dismutase(SOD) and malondialdehyde(MDA) were measured by enzyme linked immunosorbent assay(ELISA). The correlation between SOD, MDA and AMS was assessed.Results1. The effect of ascent profile on the prevalence of AMSThe prevalence of AMS among the subjects ascent by air was 62.5%, which was significantly higher than that among the subjects ascent by car(34.4%). The HR of the subjects ascent by air was significantly higher than that of the subjects ascent by car after high-altitude exposure(84±12 beats/min vs 81±10 beats/min, P<0.05).2. The relationship between age and AMS at acute altitude exposureIn the present study, 856 subjects were recruited. Except for age and BMI, there was no significant difference in smoking and drinking habits, race, and education between these groups.After a-day exposure to 3,700 m, the Lake Louise score(LLS) in the four age groups was 3.38±2.07,3.31±2.06,3.91±2.32,and 4.58±2.14, respectively. With the exception between the 18-20 years old group and the 21-25 years old group, statistical difference between other groups was observed. Similar change was observed in the incidence of AMS. Notably, the prevalence of severe AMS was increased with increasing age, and which was significant higher in the latter two groups than in the former two groups. The symptoms of AMS were more common among the older subjects.After a-day exposure to 3,700 m, the HR and BP were increased in all four age groups when compared to the values obtained before ascent, and the HR values were higher among the older subjects when compared to the values of the younger subjects. On the contrary, Sp O2 were decreased in all four age groups, and which was slightly lower among the older subjects when compared to the value of the younger subjects.Correlational analyses showed that age was positively correlated with LLS(all P<0.01), whereas Sp O2 was negatively correlated with LLS(P<0.01).Multivariate analysis showed that age was significantly associated with AMS(P<0.05 or 0.01).3. Sleep changes in insomniacs and non-insomniacs at acute altitude exposure and its relation with AMSThe age of insomniacs was significantly higher compared to that of non-insomniacs.Although resolving insomnia in few subjects, the prevalence of insomnia in insomniacs remained stable at 90% after arrival at 3,700 m. However, in non-insomniacs, the prevalence of insomnia markedly increased to 32.13% in 1st day of altitude stay, which gradually decreased to 4.26% by 60 th day of altitude stay. Furthermore, at 3,700 m, the prevalence of insomnia symptoms reduced more sharply from day 1 to day 60 in non-insomniacs than in insomniacs.Relationship between age and sleep quality was assessed using the data from “the relationship between age and AMS at acute altitude exposure”. Before ascent, Athens Insomnia Scale scores(AISSs) and the prevalence of insomnia were increased with increasing age, and reached statistical difference between the 18-20 and 31-35 years old group. After a-day exposure to 3,700 m, the AISSs in the four age groups were 4(2-7), 4(2-8), 5(3-9), and 7(4-11), respectively. With the exception between the 18-20 years old group and the 21-25 years old group, statistical difference between other groups was observed. Age was significantly correlated with AISSs(P<0.05). Similar change was observed in the prevalence of insomnia.Upon acute ascent to 3,700 m, the prevalence of AMS in insomniacs was 79.01%, 60.49%, and 32.10% on 1st, 3rd, and 7th days, respectively, which was statistically higher than that in non-insomniacs(56.07%, 27.21%, and 12.79%, respectively). Multivariate logistical regression showed that high AIS scores are a risk factor for AMS(adjusted OR 1.388, P<0.001), but high Sp O2 and long time of altitude stay are protective factors against AMS.4. Research in the prevalence of AMS of the subjects previously exposed to the RF-EMF at acute altitude exposureFirst, the baseline data of the RF-EMF exposure and control groups did not differ between groups. However, the prevalence of insomnia in the RF-EMF exposure group was slightly higher than that in the control group(16.10% vs 11.30%). After arrival at high altitude, 29 subjects lost to follow up in the RF-EMF exposure group, while 12 in the control group.Second, exposure of RF-EMF among the subjects is within the Chinese national standard(10 V/m). However, it reached the highest value(7.88±1.13 V/m) at the work place of the RF-EMF exposure subjects when the radio was on the emission status, which was significantly higher than the values obtained at other places.One day after exposure to 3,700 m, the Lake Louise score(LLS) in the RF-EMF exposure group was significantly higher than that in the control group(4.01±2.04 vs 3.29±2.15, P<0.01). Accordingly, the prevalence of AMS in the RF-EMF exposure group was higher than that in the control group(65.50% vs 52.66%, P<0.05). With regard to the prevalence of severe AMS, which was increased with the increasing RF-EMF exposure time, from 24.07%(subjects with the RF-EMF exposure time <2 years) to 52.63%(subjects with the RF-EMF exposure time >5 years). However, we did not observe the similar change in the control group. Similarly, the prevalence of AMS symptoms in the RF-EMF exposure group was higher than that in the control group. The prevalence of insomnia in the RF-EMF exposure group was slightly higher than that in the control group(50.93% vs 43.50%). The HR, BP, and cardiac output(CO) in the RF-EMF exposure group were higher than that in the control group(P<0.05 or 0.01). On the contrary, the Sp O2 and Hb in the RF-EMF exposure group were significantly lower than that in the control group(P<0.01 and 0.05, respectively). Multivariate analysis revealed that RF-EMF exposure time and HR were significantly associated with AMS.5. One possible mechanism for AMS: oxidative stressAfter acute altitude exposure, the plasma SOD level was significantly decreased(P<0.001) when compared to the values obtained before ascent, especially in persons with severe AMS; while the converse tendency was observed in MDA. Additionally, a negative correlation(ρ=-0.121, P=0.053) was observed between LLS and the plasma SOD level.Before ascent, SOD and MDA levels in the older age group of 31-35 showed slightly higher than that in the other group. After altitude exposure, the level of SOD decreased in each group, and the decreased tendency in the 31-35 years old group was more obvious, which was significantly lower than that in the 18-20 and 21-25 age group. In contrast, the level of MDA in the 31-35 age group increased most significantly, which was significantly higher than that in the 21-25 age group.Before ascent, SOD and MDA levels in the insomnia group showed a slightly higher tendency than that in the insomnia group. After altitude exposure, the level of SOD decreased in both groups, while the decreased tendency in the insomnia group was more obvious. However, the level of MDA was slightly increased in both groups, and no statistically significant difference was observed.Conclusions1. Higher ascent speed is a risk factor for AMS, and altitude acclimatization is an effective measure to reduce the prevalence of AMS.2. Upon rapid ascent to high altitude, the prevalence of main AMS symptoms, high-altitude headache, insomnia, and weakness increase with inscreasing of age, as well as the prevalence of severe AMS.3. Subjects with poor subjective sleep quality before ascent may have worse sleep after altitude exposure, including increasing the time of sleep induction, arousal during the night, and decreasing the total sleep time and quality, which may account for the increased AMS prevalence among the higher age subjects. 4. RF-EMF exposure is a risk factor for AMS. 5. Oxidative stress may be one mechanism for AMS upon rapid ascent to high altitude. |
PDF Full Text Request