| Background and Objective:The incidences of headache after arrival at high-altitude (HA) were different in the previous studies. High-altitude headache (HAH) has been described as the most frequent complaint during acute high-altitude exposure. HAH affects tourists and labor workers due to its high incidence and limitations on daily living and work. The risk factors, causes, prophylaxis and treatment of HAH are still not comprehensively understood. Thus, it is urgent to identify potential HAH risk factors to design more specific and effective medical prevention and treatment strategies for HAH and headache after high-altitude exposure.This observational study aimed to investigate factors that influence the incidence of headache after high-altitude exposure, the systemic hemodynamic characteristics of HAH and its risk factors. The study will also investigate the cerebral hemodynamic characteristics of HAH and the roles of cerebral blood flow (CBF) in acute mountain sickness (AMS).Methods:1. Subjects, who reached Golmud (HA1) by train, were divided into three groups. The second-day group experienced exercise. Eight hundred volunteers reached Lhasa (HA2) by plane and reached Yang bajing (HA3) after a 5-day rest at HA2. Data were collected on the first and fifth day at HA2 and on the first, tenth day and the sixth week at HA3. Data were obtained by structured case report form (CRF) questionnaires.2. Eight hundred fifty subjects ascended to 3700 m above sea level over a period of 2 hours by plane. Structured CRF questionnaires were used to record demographic information, systemic hemodynamic examinations, psychological scale and symptoms, including headache and insomnia a week before ascending and within 24 hours after arrival at 3700 m. Binary logistic regression models were used to analyze the risk factors for HAH.3. Transcranial Doppler (TCD) sonography examination parameters (on different cerebral vessels) of healthy lowlanders, acute exposure, short time acclimatization and long-term chronic exposure populations were collected. The subjects were recruited from 6 June 2012 to 28 June 2012. And the field trial was performed within 24 hours after their arrival at by plane in two hours 3700 in from 20 June 2012 to 28 June 2012. The baselines were examined at sea level before the ascending from 6 June 2012 to 8 June 2012. A subgroup of 163 volunteers had received the TCD examination at both sea level and 3700 m.Results:The incidence of headache at HA1 was 14.6%,35.8% and 22.2% among the three groups; however, there was no significant difference regarding incidence of headache before and after exercise (χ2=3.626,p=0.0568). Incidence of headache was 73.3% and 41.8% on the first and fifth day at HA2 (χ2= 156.02,p<0.001). The incidence of headache was higher on the first day at HA2 than that at HA1 (χ2=116.97,p<0.001). The incidence of headache on the first, third, tenth day and sixth week were 25.6%,21.1%,21.8% and 12.7% at HA3.The incidence of HAH was 73.3%. Age (p=0.011), physical labor intensity (PLI) (p =0.044), primary headache history (p<0.001), insomnia (p<0.001), arterial oxygen saturation (SaO2) (p=0.001), heart rate (HR) (p=0.002), the Self-Rating Anxiety Scale (SAS) (p<0.001) and the Epworth Sleepiness Scale (ESS) (p<0.001) were significantly different between HAH and non-HAH groups. Logistic regression models identified primary headache history, insomnia, low SaO2, high HR and SAS as independent risk factors for HAH. And cardiac output (CO) was an independent risk factor in another regression.Mean of bilateral middle cerebral artery (Vm_MCA) mean velocities and vertebral artery (Vm_vA) mean velocities and mean velocity of basal artery (Vm_BA) were higher in HAH+ group than that in HAH-group. However, only Vm_VA was significant different between HAH+and HAH-groups. However, Vm_VA (p= 0.363) and Vm_BA (p=0.272) were not significant different between AMS+ and AMS-groups, except Vm_MCA(p= 0.016) at sea level. And also, there were no significant differences in changes or percentages of change in Vm_MCA, Vm_VA and Vm_BA between AMS+ and AMS-groups.Conclusions:1. The incidence of headache at HA was reduced by acclimation to HA and the speed in which the individual reached HA. However, exercise neither increased nor decreased the incidence of headache at HA.2. The systemic hemodynamic factors, low SaO2 and high HR are related to a high probability of HAH. Additionally CO has a higher odd ratio (OR) than that of HR for HAH. Given a patient’s insomnia, primary headache history, low SaO2, high HR and high SAS score are the risk factors for HAH. Our findings will provide novel avenues for the study, prevention and treatment of HAH.3. HAH possesses a faster cerebral hemodynamic than that in non-HAH ones. CBF was significant different between AMS+ and AMS-groups. AMS score was related to CBF. However, the CBF was not so valuable in prediction of AMS. |
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