Better cardiorespiratory fitness is linked to a lower risk of dementia and depression

Being physically fit might offer protective benefits for the brain and the mind over a person’s lifespan. A recent study published in Nature Mental Health suggests that having higher levels of cardiovascular fitness is linked to a lower risk of developing conditions like depression and dementia. These findings provide evidence that keeping the heart and lungs in good shape could be an important part of maintaining long-term mental health.

Scientists conducted this study to address a gap in our understanding of how physical health affects the brain. Cardiorespiratory fitness measures how well the body absorbs and uses oxygen during sustained physical activity. Past research on this topic only synthesized a few studies at a time and focused primarily on adults with anxiety or depression.

Valentina Díaz Goñi of the Health and Social Research Center at the Universidad de Castilla-La Mancha in Spain and Bruno Bizzozero Peroni shared their motivation for the research. Bizzozero Peroni is affiliated with the same center, as well as the Karolinska Institutet in Sweden and the Universidad de la República in Uruguay. They wanted to look across the entire lifespan to understand if fitness protects against less common issues like psychotic disorders.

“This study emerged from a growing interest in understanding mental health from a preventive and integrative perspective,” the researchers noted. “While physical activity has long been linked to better mental health, we saw a need to focus on cardiorespiratory fitness specifically, as it is a more objective and comprehensive measure of how well the body can supply and use oxygen during sustained activity.” They aimed to synthesize the available evidence across multiple mental and neurocognitive disorders to better understand how strongly fitness levels are linked to long-term mental health outcomes.

To investigate this, the scientists performed a systematic review and meta-analysis. A meta-analysis is a statistical technique that combines data from multiple independent studies to identify overall trends. The researchers searched five major scientific databases for cohort studies, which are studies that track a specific group of people over time.

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They specifically looked for research involving general populations who did not have a mental or neurocognitive disorder when the studies began. The team found twenty-seven relevant studies published between 2009 and 2025. These studies tracked a massive combined sample of 4,007,638 individuals across nine different countries.

The participants came from nations including the United States, the United Kingdom, Sweden, Norway, and Taiwan. The vast majority of these individuals were categorized as white or of European ancestry. The average age of the participants at the start of the studies ranged from about ten to seventy-two years old, and they were monitored for periods ranging from four to twenty-nine years.

To measure cardiorespiratory fitness, the original studies used various testing methods. Some studies used direct oxygen consumption tests in a laboratory setting. Other studies relied on indirect exercise performance tests on treadmills or stationary bikes.

The data revealed that high levels of cardiorespiratory fitness were associated with a noticeably lower risk of developing certain mental and neurocognitive disorders. Specifically, individuals in the highest fitness category had a thirty-six percent lower risk of developing depression compared to those in the lowest category. High fitness was also associated with a thirty-nine percent lower risk of developing all-cause dementia.

The researchers found a twenty-nine percent lower risk for schizophrenia spectrum and other psychotic disorders among highly fit individuals. This specific finding was based entirely on data from two studies that only included male participants. For anxiety disorders, the combined data did not show a statistically significant protective effect from high fitness.

When looking at incremental changes, the scientists found that even small fitness gains were beneficial. “One notable finding was how consistent the associations were across different disorders, particularly for depression and dementia,” the researchers explained. “We were also struck by the fact that even modest increases in fitness, such as a 1-MET improvement, were linked to measurable reductions in risk.”

“A MET (metabolic equivalent of task) is a simple way to describe energy expenditure: 1 MET represents the energy used at rest, while light activities like slow walking require about twice that amount,” they added. “This reinforces the idea that small, achievable changes can have important long-term health benefits.” An increase of just one metabolic equivalent in a person’s fitness capacity was associated with a five percent lower risk of depression and a nineteen percent lower risk of dementia.

The researchers suggest several biological reasons why physical fitness might protect the brain. Exercise and improved fitness can increase blood flow to the brain and reduce body-wide inflammation. Chronic inflammation is known to damage brain cells and disrupt chemical signals linked to mood and memory.

Higher fitness has been linked to maintaining the volume of the hippocampus over time. The hippocampus is a specialized brain region responsible for memory formation and emotional regulation. Fitness may also support the integrity of the brain’s white matter, which acts as the communication network connecting different regions of the brain.

“The key message is that better cardiorespiratory fitness is associated with a significantly lower risk of developing conditions such as depression, dementia, and psychotic disorders,” the researchers told PsyPost. “Importantly, the benefits are not limited to highly fit individuals; even small improvements in fitness can make a meaningful difference. This suggests that incorporating regular physical activity into daily life can be a powerful and accessible way to support both physical and mental health.”

While these findings suggest a protective role for physical fitness, there are several potential misinterpretations and limitations to consider. The certainty of the evidence for depression, anxiety, and psychotic disorders was rated as very low. Meanwhile, the evidence for dementia was rated as moderate.

One major challenge in this type of research is the possibility of reverse causation. Reverse causation means that early, undetected symptoms of a mental health condition might actually cause a person to exercise less. This lack of motivation tends to lead to lower physical fitness before a formal diagnosis is ever made.

When asked about limitations, the researchers confirmed there are several. “Most of the available evidence comes from middle-aged adults in Europe and North America, so more research is needed in younger populations, older adults, and more diverse global settings,” they explained. “In addition, although the associations we observed are consistent, they should be interpreted with caution, as observational studies cannot establish definitive cause-and-effect relationships.”

They also highlighted the lack of data for certain conditions. “There is also limited evidence for several other mental disorders, such as bipolar disorder, stress-related disorders, sleep-wake disorders, and ADHD, and no available studies for some conditions like autism spectrum disorders,” they pointed out. “This means that conclusions in these areas are still uncertain and that more research is needed to fill important gaps in the evidence.”

Future research should track both fitness and mental health continuously over time to better understand which one changes first. The researchers have specific plans for advancing this field. “Moving forward, we aim to expand this research to underrepresented populations and to conduct more longitudinal studies that can better clarify causal relationships,” they stated.

“We are also interested in exploring the biological mechanisms underlying these associations, such as inflammation, brain plasticity, and stress regulation, to better understand how fitness influences mental and neurocognitive health over time,” they added. The scientists believe their work offers practical insights for society.

“Overall, we believe these findings highlight cardiorespiratory fitness as a modifiable and scalable factor that could play an important role in public health strategies,” they concluded. “Promoting physical fitness may not only help people live longer but also improve quality of life by reducing the risk of mental disorders and cognitive decline.”

The study, “Cardiorespiratory fitness and risk of mental disorders and dementia: a systematic review and meta-analysis,” was authored by Valentina Díaz-Goñi, José Francisco López-Gil, Eva Rodríguez-Gutiérrez, María Eugenia Visier-Alfonso, Estela Jiménez-López, Irene Sequí-Domínguez, Francisco B. Ortega, José Castro-Piñero, Arthur Eumann Mesas, Mairena Sánchez-López, Vicente Martínez-Vizcaíno & Bruno Bizzozero-Peroni.