Being unfit rivals smoking. Maybe worse.
People say: “Living longer takes the right biohacks” We read the study.
Cohort study. 122,007 people. 8.4 years median follow-up.
People were watched for years. Nobody was told what to do. A clue, not proof.
Who: Consecutive adults referred for a symptom-limited exercise treadmill test at Cleveland Clinic, 1991-2014 (mean age 53, 59% men); not the general population
- Slightly unfit= smoking
- Fittest vs least fit-80%
- Top 2% vs already fit-23%
More to know, from our read of the paper:
- Observational: linked, not proven
- Patients referred for a treadmill test, not the general population
- Single fitness measurement
- Unmeasured confounders (socioeconomic status, genetics)
- Measures death risk, not years of life added
Unfit rivals smoking. Linked, not proven.
- Leave the bottom 25%Half of all deaths were in it.
- Train your cardioFitness was tested on a treadmill.
- Keep climbingEvery level up: lower risk. No ceiling found.
122,007 adults did a treadmill test and were followed for about 8 years. Below-average fitness (vs above average) was linked to as much extra death risk as smoking. The fittest had 80% lower risk than the least fit, and no ceiling was found. One cohort: linked, not proven.
Mandsager et al. (2018). Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open.
Design: Cohort study · retrospective cohort study (linked, not proven)
DOI: 10.1001/jamanetworkopen.2018.3605
Goals:
We read the abstract and the full text of this paper and checked every number on this page against it (13 facts, checked on 2026-09-26). The study design is named above. Cohort and other observational studies are described as linked, not proven. Found an error? Email theis@onestudyaday.com.
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