TL;DR: ⚪ Clean null — the largest trial of its kind found 15h/day long-term oxygen therapy as effective as 24h/day for hospitalization/death at 1 year; a less burdensome regimen is sufficient.
1. Publication
- Title: Long-Term Oxygen Therapy for 24 or 15 Hours per Day in Severe Hypoxemia
- Acronym: REDOX
- Year & Journal: New England Journal of Medicine, published September 10, 2024 (391(11):977-988)
- Citation: Ekström M, Andersson A, Papadopoulos S, et al; REDOX Collaborative Research Group. N Engl J Med. 2024;391(11):977-988. doi:10.1056/NEJMoa2402638
2. Context & Rationale
Background: Long-term oxygen therapy (LTOT) ≥15h/day prolongs survival in severe chronic hypoxemia. Based on an older nonrandomized comparison, guidelines have recommended 24h/day therapy — a more burdensome regimen — without direct randomized comparison against the evidence-based 15h minimum.
Research Question/Hypothesis: In patients with severe chronic hypoxemia at rest, does LTOT for 24h/day reduce hospitalization or death within 1 year compared with 15h/day?
3. Design & Methods
- Study Type: Multicenter, phase 4, randomized, controlled trial (using the Swedish National Registry for Respiratory Failure, Swedevox, for identification)
- Setting & Centers: Sweden; May 2018–April 2022
- Population: 241 patients ≥18y meeting criteria for LTOT for chronic severe hypoxemia (mean age 76y, 59% women)
- Intervention: LTOT 24h/day (n=117)
- Comparator: LTOT 15h/day (n=124)
- Statistical Power & Follow-Up: Primary: composite of hospitalization or death within 1 year.
4. Key Results
241 patients randomized.
Outcome | 24h/day LTOT | 15h/day LTOT | Notes |
Hospitalization or death within 1 year (primary) | No significant difference | No significant difference | Clean null result |
5. Internal Validity Assessment
Registry-embedded, multicenter RCT, almost double the size of prior trials on this question combined (290 patients across earlier trials). Overall: Strong — the largest, most representative trial of this specific comparison to date, providing a clear, well-powered null result.
6. External Validity Assessment
Swedish, registry-identified population — described by the authors as "more representative of present-day patients starting long-term oxygen therapy" than prior smaller trials, supporting strong external validity for modern LTOT-eligible populations.
7. Strengths & Limitations
Strengths: Largest trial of its kind (nearly double prior combined evidence); registry-based identification improves real-world representativeness; addresses a genuine, decades-old guideline assumption based only on nonrandomized data.
Limitations: A subsequent NEJM correspondence questioned whether the findings truly challenge prior understanding, given that earlier LTOT mortality-benefit trials required longer follow-up durations to show effect — raising the possibility that 1-year follow-up may be insufficient to detect longer-term differences.
8. Interpretation & Practice Impact
Supports 15h/day as a sufficient, less burdensome LTOT regimen compared with the more demanding 24h/day approach — no disadvantage identified for the shorter regimen at 1 year, with implications for patient burden and healthcare cost (per a subsequent formal cost-effectiveness analysis).
9. Controversies & Subsequent Evidence
A NEJM correspondence exchange (Attaway/Stoller vs Ekström/Sundh) explicitly debated whether 1-year follow-up was long enough to detect a mortality difference, given that prior LTOT trials needed longer observation periods to show benefit — an important, unresolved methodological question for interpreting this specific null result. A subsequent formal cost-minimization analysis (Ssegonja et al., Ann Am Thorac Soc 2026) found the 15h/day regimen cost-effective given equivalent outcomes.
10. Summary & Executive Takeaway
Summary: REDOX randomized 241 Swedish patients with severe chronic hypoxemia to LTOT for 24h/day or 15h/day. Hospitalization or death within 1 year showed no significant difference between groups — the largest trial of this specific comparison to date.
Overall Takeaway: A less burdensome 15-hour/day oxygen therapy regimen appears as effective as 24-hour/day therapy for 1-year hospitalization/death outcomes in severe chronic hypoxemia — though debate continues about whether longer follow-up might reveal a difference, given that prior LTOT survival benefits took longer to emerge.
11. Bibliography
- Attaway AH, Stoller JK. Long-Term Oxygen Therapy for 24 or 15 Hours per Day [correspondence]. N Engl J Med. 2024;391(22):2175.
- Ssegonja R, Sundh J, Andersson A, et al. Economic evaluation of long-term oxygen therapy: the REDOX trial. Ann Am Thorac Soc. 2026;23(5):711-719.