PurposeLong-term outcomes of critical illness may be affected by duration of critical illness and intensive care. We aimed to investigate differences in mortality and morbidity after short (<8 days) and prolonged (≥8 days) intensive care unit (ICU) stay.MethodsFormer EPaNIC-trial patients were included in this preplanned prospective cohort, 5-year follow-up study. Mortality was assessed in all. For morbidity analyses, all long-stay and—for feasibility—a random sample (30%) of short-stay survivors were contacted. Primary outcomes were total and post-28-day 5-year mortality. Secondary outcomes comprised handgrip strength (HGF, %pred), 6-minute-walking distance (6MWD, %pred) and SF-36 Physical Function score (PF SF-36). One-to-one propensity-score matching of short-stay and long-stay patients was performed for nutritional strategy, demographics, comorbidities, illness severity and admission diagnosis. Multivariable regression analyses were performed to explore ICU factors possibly explaining any post-ICU observed outcome differences.ResultsAfter matching, total and post-28-day 5-year mortality were higher for long-stayers (48.2% (95%CI: 43.9% to 52.6%) and 40.8% (95%CI: 36.4% to 45.1%)) versus short-stayers (36.2% (95%CI: 32.4% to 40.0%) and 29.7% (95%CI: 26.0% to 33.5%), p<0.001). ICU risk factors comprised hypoglycaemia, use of corticosteroids, neuromuscular blocking agents, benzodiazepines, mechanical ventilation, new dialysis and the occurrence of new infection, whereas clonidine could be protective. Among 276 long-stay and 398 short-stay 5-year survivors, HGF, 6MWD and PF SF-36 were significantly lower in long-stayers (matched subset HGF: 83% (95%CI: 60% to 100%) versus 87% (95%CI: 73% to 103%), p=0.020; 6MWD: 85% (95%CI: 69% to 101%) versus 94% (95%CI: 76% to 105%), p=0.005; PF SF-36: 65 (95%CI: 35 to 90) versus 75 (95%CI: 55 to 90), p=0.002).ConclusionLonger duration of intensive care is associated with excess 5-year mortality and morbidity, partially explained by potentially modifiable ICU factors.Trail registration numberNCT00512122.