Comparison of groupsChanges of PSQI sleep factors at various time intervals following entry into a high-altitude area of 4500 m

There were notable differences in the total PSQI scores and the PSQI factor scores among groups of soldiers ascending to an altitude of 4500 m (see Table 1).

Table 1 A comparative analysis of total PSQI scores and individual factor scores at various time points during a 4500-meter stationing

The PSQI score for military personnel at an altitude of 1500 m was 5.00 (2.00,8.00); 7-day period at an altitude of 4500 m, the PSQI score increased to 11.00 (5.00,23.50). After one month, the PSQI score was recorded at 8.00 (2.75,14.25); while the PSQI score at three months was 10.00 (4.00,19.00); and at six months, it was 7.00 (3.00, 14.00). Statistically significant differences were observed in PSQI scores and daytime dysfunction across the five groups. Notably, comparisons between the 1500-meter group and the groups at 4500 m after 7 days, 1 month, 3 months, and 6 months (p < 0.05 or p < 0.01).

Subjective Sleep Quality: A significant difference was observed between the 1500 m group and the 4500 m group when assessed over periods of 7 days and 3 months (p < 0.05 or p < 0.01). Sleep Latency: The 1500 m group exhibited a statistically significant difference when compared to the 4500 m group at 1 month, as well as the 4500 m group at 7 days, 3 months, and 6 months. Sleep Efficiency: A statistically significant difference was noted between the 1500 m group and the 4500 m group after 7 days (p < 0.05). Sleep Disorders: The comparison between the 1500 m group and the 4500 m group revealed a statistically significant difference (p < 0.05 or p < 0.01). Additionally, a statistically significant difference was found between the 4500 m group after 7 days and the 4500 m group after 6 months.

Changes in gastrointestinal symptoms, sleep patterns, and emotional states at various intervals following the deployment of military personnel to an altitude of 4,500 m

Table 2 presents a comparison of the total scores of AIS and ESS at various time points following the deployment of military personnel at an altitude of 4500 m. The data indicate that among the personnel who rapidly ascended from 1500 m to 4500 m, 10 individuals (11.1%) reported experiencing insomnia at the 1500-meter mark. After being stationed at 4500 m for 7 days, 1 month, 3 months, and 6 months, the incidence of insomnia among soldiers increased to 35 (38.9%), 23 (25.6%), 30 (33.3%), and 21 (23.3%), respectively. This trend demonstrates a significant increase in the number of individuals suffering from insomnia at different intervals (7 days, 1 month, 3 months, and 6 months) when compared to the 1500-meter altitude. Notably, there was a marked rise in the number of insomniac soldiers after just 7 days of exposure to the 4500-meter altitude, with a statistically significant difference observed in comparison to the group stationed at 1500 m (p < 0.005, as shown in Table 2). At various intervals (7 days, 1 month, 3 months, and 6 months) following the rapid ascent of military personnel to an altitude of 4500 m, a decrease in the number of individuals experiencing mild to moderate sleepiness was observed in comparison to those stationed at 1500 m. conversely, the incidence of severe sleepiness among soldiers exhibited a notable increase at 4500 m after 7 days. Additionally, the prevalence of mild to moderate drowsiness diminished with the prolongation of the duration of stay at 4500 m. however, statistical analysis revealed no significant differences in somnolence across the five groups (p = 0.712, see Table 2).

Table 2 Comparison of insomnia and hypersomnia of military personnel at different altitudes and different timesChanges in gastrointestinal symptoms and emotional states at various time points following the deployment of military personnel at an altitude of 4,500 m (see Fig. 2)

At an altitude of 1500 m, 6 soldiers (6.7%) experienced diarrhea, 8 soldiers (8.9%) developed abdominal distension, and 4 soldiers (4.4%) reported constipation. Following exposure to an altitude of 4500 m for 7 days, 23 soldiers (25.6%) suffered from diarrhea, 28 soldiers (31.1%) exhibited abdominal distension, and 12 soldiers (13.3%) experienced constipation. When stationed at 4500 m for 1 month, 9 soldiers (10.0%) reported diarrhea, 33 soldiers (36.7%) experienced abdominal distension, and 15 soldiers (16.7%) had constipation. After 3 months at this altitude, 11 soldiers (12.2%) experienced diarrhea, 19 soldiers (21.1%) reported abdominal distension and 14 soldiers (15.6%) had constipation. Following 6 months of exposure to 4500 m, 37 soldiers (41.1%) reported diarrhea, 36 soldiers (40.0%) experienced abdominal distension, and 34 soldiers (37.8%) had constipation. At various time points (7 days, 1 month, 3 months, and 6 months) after ascending to 4500 m, the incidence of gastrointestinal symptoms, including diarrhea, abdominal distension, and constipation, increased in comparison to the 1500-meter altitude. Additionally, the number of soldiers experiencing insomnia rose significantly after 7 days of exposure to 4500 m, and the prevalence of gastrointestinal symptoms increased upon returning to sea level. Although the incidence of these gastrointestinal symptoms escalated with prolonged exposure to altitude, no statistically significant difference was observed between the two groups (p = 0.082, Fig. 2a).

Fig. 2

a gastrointestinal symptoms observed at various intervals following the deployment of military personnel at an altitude of 4500 m; b the emotional state of military personnel at different times after being stationed at 4500 m. SAS score: mild anxiety (scores ranging from 50 to 59 points); moderate anxiety (60 to 69 points); severe anxiety (> 70 points). SDS scores: mild depression (53 to 63 points); moderate depression (63 to 72 points); severe depression (> 72 points). Note: SAS: Self-Rating Anxiety Scale, SDS: Self-Rating Depression Scale

Correlation analysisThis study conducts a correlation analysis of PSQI total scores among military personnel who were exposed to an altitude of 4500 m for varying durations: a 7-day group, a 1-month group, a 3-month group, and a 6-month group(r)

Spearman’s rank correlation was employed to investigate the relationships among various factors, including sleep quality (PSQI score), the degree of insomnia (assessed using the AIS score), drowsiness (ESS score), and general demographic conditions (such as age, ethnicity, education, gender, and marital status). Additionally, physiological indices (including BMI, systolic blood pressure, diastolic blood pressure, and blood oxygen saturation), gastrointestinal symptoms (such as diarrhea, abdominal distension, and constipation), sleep conditions (including difficulty in falling asleep, nighttime awakenings, poor breathing, and snoring), as well as correlations between mood states (measured by the SAS scores and the SDS scores) were also examined.

In the 1500 m group (see Fig. 3), we observed significant positive correlations between age, gender, marital status, education, difficulty falling asleep, early or easy awakening during the night, poor breathing, snoring, AIS scores, ESS scores, and SAS scores (rs = 0.463, 0.251, 0.255, 0.230, 0.539, 0.641, 0.300, 0.420, 0.209, 0.606, 0.369; p < 0.001, 0.012, 0.01, 0.021, < 0.001, < 0.001, < 0.001, 0.002, < 0.001, 0.036, < 0.001, < 0.001, respectively). Conversely, no significant correlations were found with ethnicity, BMI, systolic blood pressure, diastolic blood pressure, gastrointestinal symptoms (including diarrhea, bloating, and constipation), or SDS scores. Furthermore, the total score of the AIS exhibited positive correlations with the total PSQI score, age, marital status, education, ESS score, and SAS score (rs = −0.209, 0.354, 0.433, 0.312, 0.269, and 0.232, respectively; p = 0.036, < 0.001, < 0.001, 0.002, 0.007, 0.02, respectively). However, no correlations were identified with gender, ethnicity, BMI, systolic blood pressure, diastolic blood pressure, gastrointestinal symptoms (diarrhea, bloating, constipation), difficulty falling asleep, early or easy awakening during the night, dyspnea, snoring, or SDS scores. Additionally, ESS scores were significantly and positively correlated with total PSQI scores, age, gender, marital status, education, difficulty falling asleep, early or easy awakening during the night, snoring, AIS scores, and SAS scores (rs = 0.606, 0.632, 0.399, 0.427, 0.260, 0.262, 0.337, 0.260, 0.269, and 0.283; p < 0.001, < 0.001, < 0.001, < 0.001, < 0.001, 0.009, 0.009, 0.001, 0.009, 0.007, 0.004, respectively). No correlations were found with ethnicity, BMI, systolic blood pressure, diastolic blood pressure, gastrointestinal symptoms (diarrhea, distension, constipation), dyspnea, or SDS scores.

In the 4500 m 7-day group (see Fig. 4a), the PSQI scores demonstrated a significant positive correlation with heart rate (rs = 0.233, p = 0.027). No correlations were identified with other indices. Additionally, the AIS scores exhibited positive correlations with several factors, including diarrhea, bloating, difficulty in initiating sleep, early or frequent awakenings during the night, breathing disorders, snoring, anxiety, and depression (rs = 0.371, 0.467, 0.612, 0.744, 0.716, 0.564, 0.623, and 0.521; p < 0.001). No correlations were observed with other indicators. Furthermore, the ESS scores were positively correlated with diarrhea, abdominal distension, difficulty sleeping, early or frequent awakenings at night, snoring, dyspnea, anxiety, and depression (rs = 0.257, 0.326, 0.336, 0.419, 0.529, 0.293, 0.632, 0.456, 0.339; p = 0.014, 0.002, 0.001, < 0.001, < 0.001, 0.005, < 0.001, < 0.001, 0.001). No correlations were found with other indicators.

In the 4500 m 1-month group (see Fig. 4b), PSQI scores were positively correlated with gastrointestinal symptoms (diarrhea, bloating, constipation), difficulty falling asleep, easy or early awakening during the night, dyspnea, snoring, AIS scores, ESS scores, anxiety, and depression (rs = 0.237, 0.472, 0.364, 0.613, 0.757, 0.646, 0.687, 0.868, 0.648, 0.483, and 0.459, p = 0.025 or p < 0.001); ESS was positively correlated with gastrointestinal symptoms (diarrhea, bloating, constipation), anxiety and depression (rs = 0.245, 0.407, 0.234, 0.375, 0.360; p = 0.02, < 0.001, 0.026, < 0.001), but not related to difficulty falling asleep, easy to wake up at night or early, dyspnea, snoring.

In the 4500 m 3-month group (see Fig. 4c), there was no correlation between PSQI score and diarrhea. It was positively correlated with constipation (rs = 0.273, p < 0.05), abdominal distension, difficulty falling asleep, waking up easily or waking up early at night, poor breathing, snoring, AIS score, ESS score, anxiety, and depression (rs = 0.341, 0.768, 0.720, 0.511, 0.535, 0.856, 0.521, 0.481, 0.354, respectively. p < 0.001); AIS score was positively correlated with diarrhea(rs = 0.200, p < 0.042), constipation(rs = 0.229, p < 0.02), bloating, difficulty in falling asleep, waking up easily or early during the night, dyspnea, snoring, total SAS score, and total SDS score ( rs = 0.355, 0.727, 0.758, 0.553, 0.529, 0.518, and 0.372; p < 0.001), and there was no correlation with other indicators.ESS scores were positively correlated with total PSQI score, bloating, constipation, dyspnea, snoring, total SAS score, and total SAS score (rs = 0.521, 0.260, 0.253, 0.295, 0.305, 0.334, 0.264; p < 0.001, 0.008, 0.01, 0.002, 0.002, 0.001, 0.007).

At an altitude of 4500 m for six months (refer to Fig. 4d), the total PSQI score positively correlated with various factors, including diarrhea, bloating, and constipation (rs = 0.234, p = 0.022). Additionally, the PSQI score was positively correlated with difficulty in falling asleep, instances of easy or early awakening during the night, dyspnea, snoring, scores on the AIS, and ESS, as well as levels of anxiety and depression, with correlation coefficients of rs = 0.402, 0.445, 0.708, 0.737, 0.424, 0.480, 0.756, 0.490, 0.496, and 0.352, p < 0.001).

Fig. 3

Correlation of PSQI, AIS, and ESS with various factors at an altitude of 1500 m. Note: SP: systolic pressureab, DP: diastolic pressure

Fig. 4

Military personnel exposed to altitudes of 4500 m above sea level, considering various influencing factors at different time intervals. a military personnel were exposed to an altitude of 4,500 m for seven days; b military personnel were exposed to an altitude of 4,500 m for one month; c military personnel were exposed to an altitude of 4,500 m for three months; d military personnel were exposed to an altitude of 4,500 m for seven days for six months