TOPLINE

A large UK Biobank analysis showed that even a small annual improvement in cardiorespiratory fitness among adults was independently associated with lower risks for incident cardiovascular disease (CVD) and cardiovascular mortality, whereas declining fitness was linked to a progressively higher risk in a clear dose-dependent pattern.

METHODOLOGY

• Drawing on UK Biobank data, researchers conducted a longitudinal analysis to evaluate the association between changes in cardiorespiratory fitness over time and risks for CVD and cardiovascular mortality.
• They analysed data of 11,530 adults (mean age, 56.5 years; 50.6% men) who underwent cardiorespiratory fitness assessment at baseline and again 4.3 years later.
• Cardiorespiratory fitness was assessed using a submaximal cycle ergometer protocol. Estimated maximal oxygen uptake (VO₂max; mL/kg/min) was calculated from heart rate responses during exercise using a validated assessment model.
• Outcomes were incident CVD and cardiovascular mortality. Incident CVD was identified through the UK Biobank first occurrence data resource, and cardiovascular mortality was identified from national death registry records.
• Participants were followed up over a median duration of 14.0 years from the first assessment visit until the first occurrence of the outcome of interest, death, withdrawal from the study, loss to follow-up, or administrative censoring, whichever occurred first.

TAKEAWAY

• During follow-up, 921 participants developed incident CVD and 119 died from cardiovascular causes.
• Each 1 mL/kg/min annual increase in VO₂max was associated with a 15% lower risk for incident CVD (hazard ratio [HR], 0.85; 95% CI, 0.75-0.96) and a 34% lower risk for cardiovascular mortality (HR, 0.66; 95% CI, 0.51-0.87), independent of baseline fitness, lifestyle factors, BMI changes, and genetic susceptibility.
• A clear dose-response relationship was observed, with the risk for CVD progressively decreasing as cardiorespiratory fitness improved and increasing as fitness declined over time. A significant association in the same direction was also observed for cardiovascular mortality.
• Participants with the steepest declines in VO₂max had a 33% higher risk for incident CVD and a twofold higher risk for cardiovascular death, whereas those with the greatest fitness gains had a 26% lower risk for incident CVD and a 52% lower risk for cardiovascular death.

IN PRACTICE

"From a clinical perspective, these results reinforce the importance of promoting regular moderate to vigorous physical activity as the primary strategy to improve CRF [cardiorespiratory fitness]. Additionally, they suggest that measuring CRF over time could help clinicians identify patients who are not achieving the expected physiological benefits from their reported activity levels. In such cases, more individualized exercise prescriptions, such as structured exercise programmes or supervised training, may be warranted to achieve meaningful CRF improvements," the researchers wrote.

"In clinical practice, CRF trajectories could be monitored using practical tools such as submaximal fitness tests, which are feasible for repeated administration, or through validated non-exercise equations that allow estimation from routinely available clinical data when direct testing is not possible," they added.

SOURCE

The study was led by Rubén López-Bueno, Public University of Navarra, Pamplona, Spain. It was published online on August 17, 2026, in the European Journal of Preventive Cardiology.

LIMITATIONS

The study estimated cardiorespiratory fitness using a submaximal exercise protocol rather than directly measured respiratory gas exchange, which may have underestimated the true benefit. The analysis assumed a linear trajectory of fitness over time. Detailed data on exercise type, training intensity, and training history were unavailable, which may have influenced fitness adaptations and cardiovascular outcomes.

DISCLOSURES

Funding information was not explicitly mentioned. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.