Intermittent not continuous hypoxia provoked haematological adaptations in healthy seniors: hypoxic pattern may hold the key

Purpose The purpose of this single-blind, repeated measures study was to investigate the effect of two hypoxic patterns, continuous or intermittent on key markers of haematological adaptation, stress and cardiac damage in healthy senior participants. Methods Fifteen healthy senior participants each followed a three-phase protocol over 3 consecutive weeks: (1) 5 consecutive days of breathing room air without a mask (2) 5 days of normoxic mask breathing (sham, FiO(2) = 21%) (3) 5 days of intermittent hypoxia (IH) tailored to achieve a mean peripheral oxygen saturation (SpO(2)) of 85% during 70 min of cumulative exposure to hypoxia. After a 5-month washout period, participants were recalled to undertake continuous hypoxia (CH, SpO(2) = 85%, 70 min). The red blood cell count (RBCc), haemoglobin concentration ([Hb]), haematocrit (Hct), percentage of reticulocytes (% Retics), secretory immunoglobulin A (S-IgA), cortisol, cardiac troponin T (cTnT) and the OFF-score (i.e. Hb center dot 10-60 center dot%Retics) were measured. Results RBCc only increased by day 5 of IH treatment compared to day 5 baseline values (+ 7.7%, p < 0.01) and day 5 Sham values (+ 12.9%, p < 0.01). [Hb] only increased by day 5 of IH treatment compared to day 5 baseline values (+ 14.7%, p < 0.01) and day 5 Sham values (+ 14.3%, p < 0.01). Hct (+ 12.7%, p < 0.01) and the OFF-score (p < 0.05) increased only during the final day of IH treatment. No difference was observed in S-IgA, cortisol or cTnT following IH or CH. Conclusion These results revealed that inherent differences in the IH and CH hypoxic patterns could provide crucial components required to trigger hematological changes in senior individuals, without eliciting immunological stress responses or damaging the myocardium.