High-altitude hypoxia alters the developmental trajectory of working memory in Tibetan children

Verbal working memory (WM) undergoes rapid development during school age, yet the impact of high-altitude hypoxia on this trajectory remains unclear. We propose two distinct models: the simple additive model, which posits that hypoxia imposes a uniform impairment independent of age, preserving developmental gains; the developmental trajectory reconfiguration model, which posits that hypoxia alters the typical age-related progression of WM. To test these models and explore related physiological factors, we examined WM performance and blood pressure (BP) in school-aged children across different altitudes.

A 2 × 3 between-subjects design was used, involving 535 Zang (Tibetan) students (273 fourth graders, 262 eighth graders) from three altitudes (2,200, 3,200, and 4,200 m) in Qinghai, China. WM was assessed using the Digit Span Backward (DSB) task, and BP was measured with a wrist-type electronic sphygmomanometer.

We found a significant main effect of altitude on WM [ $F_{(2,529)}=34.18,p<0.001,{\eta }_{\text{p}}^2=0.11$ ], indicating that WM in children declined markedly at altitudes around 4,200m. A significant grade-by-altitude interaction was also observed [ $F_{(2,529)}=5.38,p=0.005,{\eta }_{\text{p}}^2=0.02$ ]. Model comparison favored the developmental trajectory restructuring model over the simple additive model [ $\text{LRT}:\chi ^2{}_{\left(2\right)}=10.77,p=0.005$ ], supporting the hypothesis that high-altitude hypoxia alters the WM developmental trajectory. Further moderated regression analysis revealed a significant three-way interaction among grade, diastolic blood pressure (DBP), and altitude [ΔR ² = 0.01, F _(2,512) = 3.73, p = 0.025], suggesting that the moderating effect of DBP on WM development is altitude-dependent. Simple slope analysis showed that at 2,200 and 3,200 m, eighth graders outperformed fourth graders in WM only when DBP was at low or mean levels; at 4,200m, no significant grade differences were observed regardless of DBP level.

High-altitude hypoxia alters the developmental trajectory of verbal WM in Tibetan children, as evidenced by the disappearance of the typical grade advantage at higher altitudes and the altitude-dependent moderating role of DBP. These findings support the developmental trajectory reconfiguration model and highlight the physiological relevance of blood pressure in altitude-related cognitive development.