Cardiorespiratory fitness may cut dementia, depression and psychosis risk - medicalxpress

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Many studies carried out over the past decades have explored the relationship between mental and physical health, showing that the two are often interlinked. One well-established indicator of overall physical health is cardiorespiratory fitness, which is the ability of the heart and lungs to supply oxygen while a person is engaged in sustained physical activity.

An international team of researchers, led by the University of Castilla-La Mancha in collaboration with the Karolinska Institutet, reviewed a large pool of past studies that explored the link between cardiorespiratory fitness and numerous mental health disorders.

Their paper, published in Nature Mental Health, suggests that better cardiorespiratory fitness is associated with a significantly lower risk of developing dementia, depression, and psychotic disorders.

"Our study emerged from a growing interest in understanding mental health from a broader, preventive perspective," Dr. Bruno Bizzozero Peroni, post-doctoral researcher at Karolinska Institutet and senior author of the paper, told Medical Xpress.

"While physical activity has long been linked to better mental health, we noticed that cardiorespiratory fitness—a more objective and integrative measure of the body's ability to deliver and use oxygen during exercise—had not been systematically synthesized across mental and neurocognitive outcomes."

Exploring the link between fitness and mental health

The main goal of the recent work by Bizzozero Peroni and his colleagues was to explore the strength and consistency with which cardiorespiratory fitness is associated with the risk of developing various mental and neurocognitive disorders.

To do this, they analyzed the findings of past global studies that focused on distinct disorders, including anxiety disorders, depression, dementia, schizophrenia and other psychotic disorders, bipolar disorder, ADHD disorder, obsessive-compulsive disorder, somatic symptom disorders, and sleep–wake disorders.

"We conducted a systematic review and meta-analysis of 27 prospective cohort studies, collectively including more than 4 million participants across all age groups," explained Bizzozero Peroni.

"These studies assessed cardiorespiratory fitness—typically measured through exercise tests or estimated capacity—in individuals who were free of mental and neurocognitive disorders at baseline and then followed them over time to examine the incidence of these conditions."

By pooling the results of these 27 research studies, the team was able to quantify the associations between high vs. low cardiorespiratory fitness and the risk of developing different mental health and neurocognitive conditions. To estimate the risk that the people included in the pooled dataset would develop specific disorders over time, the team calculated so-called hazard ratios (HR).

"We also specifically examined studies that reported associations per 1-MET increase in cardiorespiratory fitness, allowing us to assess whether even small improvements in fitness were linked to reduced risk," said Bizzozero Peroni.

"A MET (metabolic equivalent of task) is a unit that reflects the energy cost of physical activity—for example, roughly the difference between resting and very light activities such as slow walking."

The researchers' analyses revealed that better (vs. worst) cardiorespiratory fitness was consistently associated with a substantially lower risk of developing various disorders in adulthood. Specifically, it was found to be linked to a 36% lower risk of depression, 39% lower risk of dementia, 29% lower risk of psychotic disorders, and a 10% lower risk of anxiety (even if the association was not statistically significant in this case).

"For other mental health outcomes, the available evidence was limited to single studies, which prevented us from conducting pooled analyses and drawing robust conclusions," said Bizzozero Peroni.

"In addition, most of the evidence comes from middle-aged adult populations, highlighting the need for more longitudinal research in children, adolescents, young adults and older adults."

Interestingly, Bizzozero Peroni and his colleagues found that even modest improvements in fitness, such as an increase of one MET, were linked to significant reductions in risk—about 5% for depression and 19% for dementia.

This suggests that the benefits of cardiorespiratory fitness for mental health are not exclusive to highly athletic individuals, but that they could instead also be achieved at a general population level via fitness-based interventions.

Informing mental health prevention programs

The results of the team's systematic review and meta-analysis could soon inspire further research exploring the mechanisms underlying the link between fitness-related measures and psychiatric or neurocognitive disorders. In addition, they could inspire the development of new interventions or preventative programs for specific disorders that focus on improving people's fitness levels.

"From a public health perspective, these findings highlight cardiorespiratory fitness as a measurable, modifiable and scalable factor that could play a key role in prevention," said Bizzozero Peroni. "It supports the idea of integrating fitness assessment into routine health evaluations, including mental health."

As part of their future studies, Bizzozero Peroni and his colleagues would like to perform further analyses that include data collected from underrepresented populations. For instance, they would like to explore the link between cardiorespiratory fitness and mental health in children, adolescents, young adults, older adults and people living outside of Europe or North America.

"This will be essential to ensure that findings are globally applicable and reflect different life stages," explained Bizzozero Peroni.

"In addition, there is a need for more robust longitudinal epidemiological studies to strengthen causal inference and better understand how cardiorespiratory fitness influences the development of mental and neurocognitive disorders over time.

"Finally, we are interested in further exploring the underlying biological mechanisms—such as neuroplasticity, inflammation and stress regulation—that may help explain these associations within population-based research frameworks." 

by Ingrid Fadelli, Medical Xpress

edited by Sadie Harley, reviewed by Robert Egan 

Source: Cardiorespiratory fitness may cut dementia, depression and psychosis risk