Table 5.
Explained between study heterogeneity (EH) by selected variables from univariate and multivariate meta-regression for high and extreme altitudes.
| Model | N | PMC in BW | EH | p value | N | PMC in FFM | EH | p value | N | PMD in FM | EH | p value |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (in kg with 95% CI) | (in kg with 95% CI) | (in kg with 95% CI) | ||||||||||
| High altitude Univariate | ||||||||||||
| Manipulation of diet/ hypocaloric diet |
38 | 1.00 (-0.27, 2.27) | 21% | 0.12 | 14 | 0.60 (-0.53, 1.73) | 42% | 0.26 | 13 | 0.91 (-0.91, 2.74) | 25% | 0.29 |
| –4.47 (-7.50, -1.44) | <0.01 | –2.32 (-4.32, -0.33) | 0.03 | –2.45 (-5.31, -0.41) | 0.09 | |||||||
| Duration (days) | 38 | –0.08 (-0.16, -0.12) | 20% | 0.02 | n.s. | n.s. | ||||||
| Baseline bodyweight | 37 | –0.08 (-0.17, -0.02) | 0.4% | 0.13 | n.s. | n.s. | ||||||
| Sex (male) | 38 | –0.02 (-0.042, -0.003) | 13% | 0.02 | 13 | –0.02 (-0.03, -0.003) | 66% | 0.02 | n.s. | |||
| Exposure (active) | n.s. | n.s. | 13 | –1.65 (-3.27, -0.04) | 30% | 0.05 | ||||||
| Multivariate | 38 | 35% | 13 | 42% | ||||||||
| Manipulation of diet/ | 0.94 (-0.25, 2.12) | 0.12 | Insufficient no. of observations | |||||||||
| hypocaloric diet | –4.01 (-6.96, -1.06) | <0.01 | ||||||||||
| Duration (days) | –0.07 (-0.14,.004) | 0.05 | ||||||||||
| Sex (male) | –0.02 (-0.05,.006) | 0.11 | ||||||||||
| Exposure (active) | –2.19 (-3.86, -0.53) | 0.04 | ||||||||||
| Extreme altitude Univariate | ||||||||||||
| Duration (days) | 11 | –0.05 (-0.12, -0.02) | 14% | 0.12 | n.s. | 6 | –0.04 (-0.11, 0.03) | 42% | 0.14 | |||
| Baseline bodyweight | 8 | –0.53 (-0.86, -0.21) | 84% | <0.05 | n.s. | n.s. | ||||||
| Age (years) | n.s. | n.s. | –0.22 (-0.41, -0.02) | 77% | 0.04 | |||||||
| Multivariate | 8 | 84% | Insufficient no. of observations | Insufficient no. of observations | ||||||||
| Duration (days) | –0.01 (-0.09, 0.07) | 0.65 | ||||||||||
| Baseline bodyweight | –0.43 (-0.92, -0.05) | 0.07 | ||||||||||
| Altitude (per 1000 m) | –1.10 (-5.17, 2.98) | 0.50 |
Univariate, univariate meta-regression results; multivariate, multivariate meta-regression results; N, number of observations; PMC, pooled mean change; EH, explained heterogeneity in percentage; BW, body weight; FFM, fat free mass; FM, fat mass; MM muscle mass; moderate altitude (1500-3500 m), high altitude (3500-5300 m), extreme altitude (>5300 m); n.s., non-significant results for selected variable in meta-regression analysis; Manipulation of diet/hypocaloric diet was analyzed as one single covariate and compared to non-manipulation of diet; exposure, compared to passive exposure.