Cohort2018 · JAMA Network Open · Mandsager K et al.
No upper limit to fitness: 122,007 exercise tests
Who, how long
122,007 patients at Cleveland Clinic, 8.4 years of follow-up
What they found
The fittest 2.3% had 80% lower mortality than the least fit; low fitness was a bigger risk than smoking, diabetes or heart disease.
⚠ Caveat
Observational: patients referred for exercise testing aren't a random sample; reverse causation (sick people are unfit) may explain part.
Related in the knowledge base
Last reviewed: 6 September 2026
This site is educational and does not replace medical advice. Start any supplement or drug only after consulting a doctor or pharmacist.