Parameter estimates for changes in ln(Hbmass) from baseline (prealtitude) values during altitude exposure, derived via linear mixed modelling, and their interpretation in terms of percentage changes (increases) in Hbmass
| Model/parameter | Change in ln(Hbmass) from prevalues | Percentage of increase in Hbmass | ||||
|---|---|---|---|---|---|---|
| Estimate | 95% CI | p Value | Time at altitude (h) | Estimate | 95% CI | |
| Linear* | ||||||
| slope | 1.07×10−4 | (0.94×10−4 to 1.20×10−4) | <0.001 | 100 | 1.08 | (0.94 to 1.21) |
| Quadratic* | ||||||
| Linear | 1.39×10−4 | (1.10×10−4 to 1.69×10−4) | <0.001 | 100 | 1.33 | (1.10 to 1.56) |
| Quadratic | −7.59×10−8 | (−13.95×10−8 to −1.23×10−8) | 0.021 | 200 | 2.52 | (2.14 to 2.89) |
| 300 | 3.56 | (3.13 to 4.00) | ||||
| Time as a factor (h) | ||||||
| 18–24 | 0.22×10−4 | (−0.80×10−4 to 1.23×10−4) | 0.664 | 18–24 | 0.22 | (−0.80 to 1.24) |
| 96–112 | 1.29×10−4 | (0.66×10−4 to 1.93×10−4) | <0.001 | 96–112 | 1.30 | (0.66 to 1.95) |
| 144–224 | 2.41×10−4 | (1.82×10−4 to 3.01×10−4) | <0.001 | 144–224 | 2.44 | (1.84 to 3.06) |
| 266–294 | 3.25×10−4 | (2.50×10−4 to 4.00×10−4) | <0.001 | 266–294 | 3.30 | (2.53 to 4.08) |
| 312–364 | 3.89×10−4 | (3.09×10−4 to 4.70×10−4) | <0.001 | 312–364 | 3.97 | (3.14 to 4.81) |
| 408–456 | 4.00×10−4 | (2.91×10−4 to 5.09×10−4) | <0.001 | 408–456 | 4.08 | (2.95 to 5.22) |
| 504–672 | 6.28×10−4 | (4.96×10−4 to 7.59×10−4) | <0.001 | 504–672 | 6.48 | (5.09 to 7.89) |
*For the linear and quadratic models, the time at altitude is measured in hours so that, for example, the linear model implies an increase in ln(Hbmass) of 0.0107/100 h, which translates to an increase of 1.08% in Hbmass.
p Values refer to testing whether the associated parameter is equal to zero.
Hbmass, haemoglobin mass; ln(Hbmass); natural log of Hbmass.