Two awardees selected for the KI Lifestyle4Health Best Paper Award 2022

• “Improvements in Maximal Oxygen Uptake After Sprint-Interval Training Coincide with Increases in Central Hemodynamic Factors” by Mirko Mandic et al.

• “Healthy Lifestyle and Mortality Among Adults Receiving Hemodialysis: The DIET-HD Study” by Guobin Su et al.

Award Ceremony

An award ceremony was held on November 21^st, 2022 in Biomedicum, where the authors presented their work and had the opportunity to have a lively discussion with the audience.

About the authors

Mirko Mandic is a PhD student at the division of Clinical Physiology at Karolinska Institutet. His research focuses on central hemodynamical adaptations to exercise with a special focus on the adaptations of the blood volume, circulation and the heart.

Guobin Su is a medical doctor in Nephrology, Associate Professor in research at Department of Nephrology, Guangdong Provincial Hospital of Chinese Medicine, affiliated researcher at the Medical Epidemiology and Biostatistics, Karolinska Institutet. His reseach interest includes healthy lifestyle for better kidney health, pharmocoepidemiology (including Chinese medicine) in chronic kidney disease and acute kidney injury, infection and kidney disease. He defended his PhD at the Department of Global Public Health at KI.

Popular science summaries

“Improvements in Maximal Oxygen Uptake After Sprint-Interval Training Coincide with Increases in Central Hemodynamic Factors” by Mirko Mandic et al.

Two of the most popular forms of interval training are high-intensity interval training (HIIT) and sprint interval training (SIT).

SIT has proven to be an effective form of training when it comes to increasing maximal oxygen consumption (VO2max). Despite the low time expenditure (≈10 minutes), the exercise-induced effects after SIT interventions are equivalent to those after training programmes involving traditional endurance exercises with a time expenditure per session 3 to 4 times higher.

Previous research has shown that SIT has a pronounced effect on peripheral adaptations. These adaptations primarily affect the ability of skeletal muscles to obtain and use oxygen during exercise. However, less is known about the central haemodynamic effects following SIT. Central adaptations include total blood volume and total haemoglobin mass, to name a few, both of which play an important role in oxygen delivery to the working muscle. The lack of knowledge about the central factors that influence VO2max is problematic, as many of the long-term health benefits associated with VO2max are thought to be mediated by central adaptations.

In our study, we investigated how central factors responsible for oxygen delivery (total haemoglobin mass, blood volume, maximal cardiac output) would contribute to the expected improvements in cardiorespiratory fitness after a 6-week training intervention consisting of SIT.

The study involved younger, healthy participants. Each training session consisted of 10 minutes of low intensity cycling interspersed with 3 x 30 seconds all-out sprints.

As expected, VO2max increased (10.3%) after the training intervention. Specific haemodynamic factors that improved were total haemoglobin mass, maximum cardiac output and total blood volume, with total haemoglobin mass in particular correlating with the improvement in VO2max. These results suggest that SIT -induced improvements in VO2max are mediated by both peripheral and central factors. Both the changes in VO2max and many of the underlying adaptive mechanisms are thus comparable to those of conventional endurance training.

In our opinion, this means that the similarity between SIT and conventional endurance training in terms of training effects and the adaptations that mediate these effects is greater than previously thought. In practise, this would allow for a broader and more interchangeable use of intervals in training programmes without fear of missing key haemodynamic adaptations.

“Healthy Lifestyle and Mortality Among Adults Receiving Hemodialysis: The DIET-HD Study” by Guobin Su et al.

About one in ten of the world population and around 8.5 billion people suffers from some kind of chronic kidney disease. More than 2.5 million individuals worldwide require dialysis to support life. However, the prognosis of patients on dialysis remains very poor, with an annual mortality of 10% to 20%, largely due to cardiovascular diseases.

Despite these alarming figures, there is no evidence-based guidance on whether and what lifestyle changes can help to reduce risk of death in this specific population. Current advice to patients is based on lifestyle recommendation in patients with cardiovascular disease, which are considered important causes of
death in patients with dialysis. These include avoiding smoking, engaging in regular physical activity, adhering to a healthy diet (rich in fruits, vegetables, and fish and low in salt and sugar), and maintaining blood pressure (BP) within recommended targets. It is uncertain if this is also true within the hemodialysis population.

Researchers from Sweden, China and Australia have conducted a multi-nation cohort study of more than 5,483 dialysis patient across Europe and South America to investigate which lifestyle changes (measured by a composite of smoking, physical activity, diet, and systolic blood pressure and individually) can lower the risk of death.

“We discovered that lifestyle plays a big role in survival benefit in dialysis patients” says Dr. Guobin Su, a postdoctoral research fellow at Karolinska Institutet. Compared with patients who had a low lifestyle score (such as those who smoke, are sedentary, do not follow a healthy diet, and have high BP [≥140 mm Hg]), participants with high lifestyle scores had a 36% and 35% lower risk of all-cause and cardiovascular death, respectively. However, only the stopping smoking and being physically active recommendation propose survival benefit in the dialysis patients. Adherence to the diet and blood pressure target/recommendation for patients with cardiovascular disease from American Heart Association did not convery survival benefit in patients undergoing maintenance dialysis.

These findings may encourage clinicians to recommend to their hemodialysis patients that they adopt a healthy lifestyle that includes stopping smoking and being physically active. Specific diet and blood pressure target needs further study in dialysis patients.