Why Fitness Matters More Than We Think
Living longer is one of the great successes of modern medicine. Yet with longer lives has come a growing challenge: multimorbidity—the experience of having two or more chronic diseases at the same time. Conditions like diabetes, heart disease, high blood pressure, and depression often cluster together, especially as we age. Today, about one-third of adults worldwide live with multimorbidity, a figure that rises steeply in older age.
Scientists have long known that cardiorespiratory fitness—our body’s ability to deliver oxygen during sustained activity—offers protection against individual diseases like heart disease and diabetes. But one big question has remained: Can better fitness slow or prevent the overall accumulation of chronic diseases as people age?
A new longitudinal study suggests the answer is yes.
Inside the Study: 38,000 People, 15 Years of Health Data
A new study led by Abigail Dove and colleagues from Karolinska Institutet, followed more than 38,000 adults for up to 15 years to examine how fitness relates to long-term health. Researchers analyzed health data from 38,348 adults enrolled in the UK Biobank, with an average age of about 55. Importantly, all participants began the study without any diagnosed chronic diseases. Their cardiorespiratory fitness (CRF) was measured through a simple 6-minute cycling test and categorized as low, moderate, or high, accounting for age and sex.
Participants’ health was then tracked for up to 15 years, monitoring the onset of 59 different chronic diseases, grouped into:
- Metabolic diseases (e.g., diabetes, obesity, high blood pressure)
- Cardiovascular diseases (e.g., heart failure, stroke)
- Neuropsychiatric diseases (e.g., depression, dementia)
Multimorbidity was defined as developing two or more of these conditions.
The Key Findings
Over the follow-up period:
- 40% of participants developed multimorbidity.
But fitness levels made a meaningful difference:
- Those with high CRF had a 21% lower risk of developing multimorbidity compared to those with low CRF.
- Multimorbidity developed 1.27 years later in the high-fitness group on average.
- High-fitness participants accumulated chronic diseases more slowly, especially metabolic diseases.
Even moderate fitness helped:
- The moderate CRF group saw a 10% reduction in multimorbidity risk.
- Their onset of multimorbidity was delayed by about half a year.
Crucially, fitness mattered across life stages—but the benefits were stronger for people under 60, suggesting middle age may be a key window for prevention.
Why Might Fitness Slow Disease Accumulation?
Cardiorespiratory fitness reflects the combined health of the heart, lungs, blood vessels, and muscles. Higher fitness is associated with:
- Lower long-term inflammation
- Better blood pressure and glucose regulation
- Stronger heart and vascular function
- Less visceral fat (the type most linked to disease)
- Improved mental health resiliency
This means fitness isn’t just about endurance—it signals that the body’s core systems are functioning more efficiently and more resiliently over time.
What This Means for Healthy Aging
Multimorbidity contributes to disability, reduced independence, and higher healthcare costs. So delaying or preventing it—even by one year—has meaningful personal and societal impact.
This study suggests that:
- Fitness should be treated as a vital sign, not just a lifestyle choice.
- Improving fitness in midlife may produce the largest long-term benefits.
- You don’t need to be an athlete—moving from low to moderate fitness already helps.
- The most encouraging message? Cardiorespiratory fitness is changeable at any age.
Activities that improve CRF include:
- Brisk walking,
- Cycling,
- Swimming,
- Jogging,
- Group aerobics,
- or any sustained activity that raises the heart rate.
Even short, regular bouts of activity can build up meaningful fitness improvements over time.
A Simple Takeaway
This long-term study reinforces a powerful idea: Fitness influences not just how long we live, but how well we live as we age. Higher cardiorespiratory fitness doesn’t just reduce the risk of individual conditions—it slows the entire process of chronic disease accumulation.
In other words, maintaining cardiorespiratory fitness is one of the most effective tools we have to support healthy longevity.
The study is published in the journal JACC: Advances. It was led by Abigail Dove from Karolinska Institutet.
