Characteristics of tourists suffering from mountain sickness
Gender distribution of tourists
The proportion of male tourists with altitude sickness increased year by year (P < 0.001) and that of the female patients increased first and decreased later (P < 0.001). The ratio of males to females rose from 0.66:1 to 0.94:1 (Table 1).
Table 1
Year
|
Male (%)
|
Female (%)
|
Gender Ratio
|
Total (%)
|
2015
|
37 (39.78)
|
56 (60.22)
|
0.66:1
|
93 (100.00)
|
2016
|
61 (44.20)
|
77 (55.80)
|
0.79:1
|
138 (100.00)
|
2017
|
63 (48.46)
|
67 (51.54)
|
0.94:1
|
130 (100.00)
|
Total
|
161
|
200
|
-
|
361
|
Value
|
322.000***
|
400.000***
|
-
|
-
|
Age distribution of tourists
The age group composition changed over the 3-year study period. The proportion of the age group with individuals under 10 years old and that of individuals between 10 and 20 years old first decreased and later increased (P < 0.001). The proportion of the 20-30 age group and the 30-40 age group first increased and decreased then (P=0.000), but the number of patients increased yearly. The proportion of the 40-50 age group and the 50-59 age group decreased year by year (P < 0.001). The proportion and the number of patients of the 60-69 age group first decreased and later increased (P < 0.001). The proportion and the number of patients of the over 70 age group first increased and later decreased (P < 0.001) (Table 2).
Table 2
Year
|
‹10
|
10-19
|
20-29
|
30-39
|
40-49
|
50-59
|
60-69
|
≥70
|
Total
|
2015
|
5
(5.38)
|
3
(3.23)
|
4
(4.30)
|
6
(6.45)
|
22
(23.66)
|
35
(37.63)
|
12
(12.90)
|
6
(6.45)
|
93
(100.00)
|
2016
|
2
(1.45)
|
1
(0.72)
|
12
(8.70)
|
15
(10.87)
|
26
(18.84)
|
45
(32.61)
|
32
(23.19)
|
5
(3.62)
|
138
(100.00)
|
2017
|
4
(3.08)
|
7
(5.38)
|
13
(10.00)
|
14
(10.77)
|
21
(16.15)
|
36
(27.69)
|
29
(22.31)
|
6
(4.62)
|
130
(100.00)
|
Total
|
11
|
11
|
29
|
35
|
69
|
116
|
73
|
17
|
361
|
Value
|
22.000***
|
22.000***
|
58.000***
|
70.000***
|
138.000***
|
232.000***
|
146.000***
|
17.000***
|
-
|
Distribution of mountain sickness disease types
The altitude was classed according to the 500-metre intervals, and the cases in the study were distributed throughout a range of 3 altitude classes (Table 3). AMS was the most frequent disease type, which mainly occurred in the 2nd and 3rd altitude classes. HAPE, HAHD were the main disease types. HAPE mainly occurred in the 2nd and 3rd altitude classes. HAHD mainly occurred in the 2nd and 3rd altitude classes. No incidents of HACE were recorded in the cases.
Table 3
Class
|
AMS
|
HAPE
|
HAHD
|
Total
|
First
|
31(91.18)
|
3(8.82)
|
0(0.00)
|
34
|
Second
|
129(91.49)
|
10(7.09)
|
2(1.42)
|
141
|
Third
|
171(91.94)
|
11(5.91)
|
4(2.15)
|
183
|
Total
|
331
|
24
|
6
|
361
|
Value
|
662.000***
|
48.000***
|
6.000*
|
-
|
During the three years, the proportion of AMS decreased yearly, but the number of patients first increased and then decreased (P < 0.001). The proportion and the number of HAPE increased yearly (P < 0.05). The proportion of HAHD first decreased and then increased, but the number of patients was still 2. (Table 4).
Table 4
Year
|
AMS
|
HAPE
|
HAHD
|
Total
|
2015
|
87(93.55)
|
4(4.30)
|
2(2.15)
|
93(100.00)
|
2016
|
128(92.75)
|
8(5.80)
|
2(1.45)
|
138(100.00)
|
2017
|
116(89.23)
|
12(9.23)
|
2(1.54)
|
130(100.00)
|
Total
|
331
|
24
|
6
|
361
|
Value
|
662.000***
|
48.000***
|
-
|
-
|
Distribution of mountain sickness symptoms
As seen in Table 5, the most frequent symptoms of mountain sickness included vomiting, headache, dizziness, hypoxia, chest tightness, nausea and malaise. The symptoms occurred in different parts of the body, including the chest, lower limbs, limbs, head, abdomen, neck and body. Among the head symptoms, dizziness was the most common (8; 11.43%), hypoxia (6; 8.57%) and headache (4; 5.71%) were also common. Among the chest symptoms, chest tightness (4; 5.71%) was the main disease, and angina pectoris, arrhythmia, haemoptysis and chest pain (1; 1.43%) occurred. In the limbs, trembling limbs and limb weakness (1; 1.43%) were the main symptoms. For the abdomen, vomiting (13; 15.24%), nausea (7; 10.00%) and Gastrectasia (2; 2.86%) were the main symptoms. Malaise (8; 11.43%) was the most frequent of all symptoms that occurred in the whole body, followed by dehydration and muscle pain (1; 1.43%). Other types included blunt force injury (1; 1.43%).
Table 5
Body part
|
Symptom
|
No.
|
Body part
|
Symptom
|
No.
|
Head
|
Dizziness
|
8(11.43)
|
Chest
|
Chest tightness
|
4(5.71)
|
Hypoxia
|
6(8.57)
|
Angina pectoris
|
1(1.43)
|
Headache
|
4(5.71)
|
Chest pain
|
1(1.43)
|
Fainting
|
1(1.43)
|
Arrhythmia
|
1(1.43)
|
Nose bleeding
|
1(1.43)
|
Haemoptysis
|
1(1.43)
|
Carsickness
|
1(1.43)
|
Limbs
|
Limb weakness
|
1(1.43)
|
Cerebral apoplexy
|
1(1.43)
|
Trembling limbs
|
1(1.43)
|
Whole body
|
Malaise
|
8(11.43)
|
Abdomen
|
Vomiting
|
13(18.57)
|
Dehydration
|
1(1.43)
|
Nausea
|
7(10.00)
|
Muscle pain
|
1(1.43)
|
Gastrectasia
|
2(2.86)
|
Neck
|
Neck swelling
|
1(1.43)
|
Gastrorrhagia
|
1(1.43)
|
Genitals
|
Haemorrhage
|
1(1.43)
|
Others
|
Blunt force injury
|
1(1.43)
|
Lower limbs
|
Inability to walk
|
1(1.43)
|
|
|
|
Temporal distribution of mountain sickness
In response to the growth rate of tourists in the case area, the number of tourists suffering from mountain sickness increased from 2015 to 2017, which had 93, 138 and 130 incidents, respectively. As seen in Figure 1, the number of tourists was lowest in February. From March to June, it grew rapidly. The highest peak usually occurred in June and July. The number of tourists decreased slightly in August and September, and it increased in October and then declined after November.
Spatial distribution of mountain sickness
As seen in Figure 2, the quantitative range of tourists suffering from mountain sickness was unevenly distributed in space, which was mainly concentrated in high-altitude regions in Western China, such as the Tibet Autonomous Region, Sichuan Province and Qinghai Province. In particular, the incidence of mountain sickness was concentrated in one or several cities in the above provinces, such as Lhasa, Ngawa and Garzê. There were no cases or cases occurred below 2500 m in the cities, which are shown in white in Figure 2.
According to the abovementioned altitude classification, the mountain sickness in the study period was statistically analysed. Within the three-year period, the proportion of mountain sickness cases from 2500 m to 3000 m (1st class) first decreased and later increased (P < 0.001), and the number of patients increased. The proportion of mountain sickness cases and the number of patients first increased and later decreased from 3000-3500 m (2nd class) (P < 0.001). The proportion of mountain sickness above 3500 metres (3rd class) first decreased and then increased, and the number of patients with mountain sickness increased slightly (P < 0.001) (Table 6).
Table 6
|
Classification of Altitude
|
|
Year
|
First
|
Second
|
Third
|
No.
|
2015
|
10
(10.75)
|
21
(22.58)
|
62
(66.67)
|
93
(100.00)
|
2016
|
10
(7.25)
|
67
(48.55)
|
61
(44.20)
|
138
(100.00)
|
2017
|
14
(10.77)
|
53
(40.77)
|
63
(48.46)
|
130
(100.00)
|
Total
|
34
|
141
|
186
|
361
|
Value
|
34.000***
|
282.000***
|
372.000***
|
-
|
As seen in Table 7, Tibet (197, 54.57%) ranked first among the provinces with large numbers of tourists, and Sichuan ranked second (137, 37.95%) followed by Qinghai (23, 6.37%), Gansu (3, 0.83%). In addition, a small number of mountain sickness cases occurred in Xinjiang (1, 0.28%). The cases of mountain sickness that occurred in Tibet were mainly concentrated in Lhasa (165, 45.71%) and Linzhi (25, 6.93%). The cases in Sichuan were mainly concentrated in Ngawa (79, 21.88%) and Garzê (58, 16.07%). Qinghai’s mountain sickness incidence areas were mainly concentrated in Haibei (14, 3.88%), Hainan (7, 1.94%) and Haixi (2, 0.55%). Gansu’s were mainly concentrated in Gannan (3, 0.83%).
Table 7
Province
|
City
|
No.
|
Class
|
Province
|
City
|
No.
|
Class
|
Gansu
|
Gannan Tibetan
Autonomous
Prefecture
|
3(0.83)
|
1
|
Tibet
|
Ngari
Prefecture
|
3(0.83)
|
3
|
Qinghai
|
Tibetan Autonomous Prefecture of Haibei
|
14(3.88)
|
3
|
Lhasa
|
165(45.71)
|
3
|
Haixi Mongolian and Tibetan Autonomous Prefecture
|
2(0.55)
|
1
|
Linzhi
|
25(6.93)
|
1
|
Tibetan Autonomous Prefecture of Hainan
|
7(1.94)
|
1
|
Changdu
|
1(0.28)
|
2
|
Sichuan
|
Tibetan Qiang Autonomous Prefecture of Ngawa
|
79(21.88)
|
2
|
Shannan
|
1(0.28)
|
3
|
Tibetan Autonomous
Prefecture of Garzê
|
58(16.07)
|
2
|
Rikaze
|
2(0.55)
|
3
|
Xinjiang
|
Bayingol Mongolian Autonomous Prefecture
|
1(0.28)
|
3
|
|
|
|
|
Figure 3 shows the altitude class of each city. The 1st class mainly covered Tibet and Qinghai, including Linzhi, Hainan and Haixi (Table 6). The 2nd class covered Gansu, Sichuan and Tibet, including Ngawa, Garzê, Changdu, Gannan. The 3rd class covered Tibet, Xinjiang and Qinghai, including Ngari. Lhasa, Rikaze, Shannan, Bayingol and Haibei.