Medical Bulletin 30/May/2025

Here are the top medical news for the day: 

Study Reveals How Your Daily Rhythm Affects Aging and Wellness

A new study published in Medicine & Science in Sports and Exercise reveals that the timing and consistency of daily activity may significantly impact heart and lung health in older adults. The research found that earlier and more regular activity patterns were associated with better cardiorespiratory fitness and walking efficiency—two key indicators of healthy aging. Although the findings are observational and do not prove causation, they open new possibilities for personalized health strategies based on an individual’s internal clock.

The circadian rhythm, or internal biological clock, regulates sleep-wake cycles and various physiological and metabolic processes. To explore its connection to physical fitness, researchers enrolled about 800 independent older adults with an average age of 76. Participants wore wrist devices that continuously tracked their daily movement over seven days. Their heart and lung health were then evaluated through cardiopulmonary exercise testing, providing a comprehensive assessment of cardiorespiratory function.

Key outcomes of the study showed that higher-amplitude activity and rest cycles-meaning greater activity during waking hours relative to rest periods—were linked to improved fitness and walking efficiency. Participants who reached peak activity earlier in the day and maintained consistent daily schedules also demonstrated better health outcomes. Activity was broadly defined to include all forms of movement, such as walking, gardening, shopping, or cleaning-not just formal exercise.

"While we've long known that being active supports healthy aging, this study reveals that when you're active may also matter," said Karyn Esser, Ph.D., senior author and chair of the UF College of Medicine's Department of Physiology and Aging. Esser emphasized that although her study suggests a link between earlier, consistent activity and better health, it doesn't prove that following such a schedule will improve health and fitness.

"Each of us has a chronotype-a biological tendency to be more alert in the morning or evening=and that variation may play a significant role in our health," Esser said.

Reference: Melissa L. Erickson, Terri L. Blackwell, Reagan E. Garcia, Theresa Mau, Peggy M. Cawthon, Steven R. Cummings, Samaneh Farsijani, Lauren M. Sparks, John Noone, Nancy W. Glynn, Anne B. Newman, Karyn A. Esser. Rest Activity Rhythms and their Association with Cardiorespiratory Fitness and Walking Energetics in Older Adults: Study of Muscle, Mobility and Aging. Medicine & Science in Sports & Exercise, 2025; DOI: 10.1249/MSS.0000000000003730

Cannabis Use May Harm Heart Like Tobacco: Study Finds

A new study has found that chronic cannabis use, whether it's smoked or consumed in edible form, is associated with significant cardiovascular risks.

The report, published in JAMA Cardiology, found that people who regularly used marijuana in either form had reduced blood vessel function that was comparable to tobacco smokers. Vascular function in those who used cannabis by either means was reduced roughly by half compared to those who did not use it. Decreased vascular function is associated with a greater risk of heart attack, hypertension, and other cardiovascular conditions.

The researchers recruited 55 people between October 2021 and August 2024 who were outwardly healthy and either regularly smoked marijuana or consumed edibles containing tetrahydrocannabinol (THC), the primary psychoactive compound found in cannabis.

The participants, none of whom used any form of nicotine, consumed cannabis at least three times a week for at least a year. Smokers averaged 10 years of chronic use, and those who took edibles averaged five years.

Along with decreased vascular function, marijuana smokers had changes in their blood serum that were harmful to endothelial cells, which form the inner lining of all blood and lymphatic vessels. Those who took edibles containing tetrahydrocannabinol, however, did not display these changes in blood serum.

These results suggest smoking marijuana negatively affects vascular function for different reasons than ingesting tetrahydrocannabinol does, according to first author Leila Mohammadi, MD, PhD, and senior author Matthew L. Springer, PhD.

Reference: Leila Mohammadi, Mina Navabzadeh, Nerea Jiménez-Téllez, Daniel D. Han, Emma Reagan, Jordan Naughton, Lylybell Y. Zhou, Rahul Almeida, Leslie M. Castaneda, Shadi A. Abdelaal, Kathryn S. Park, Keith Uyemura, Christian P. Cheung, Mehmet Nur Onder, Natasha Goyal, Poonam Rao, Judith Hellman, Jing Cheng, Joseph C. Wu, Gregory M. Marcus, Matthew L. Springer. Association of Endothelial Dysfunction With Chronic Marijuana Smoking and THC-Edible Use. JAMA Cardiology, 2025; DOI: 10.1001/jamacardio.2025.1399

Systematic Review Reveals Why That Morning Glass of Fruit Juice May Do More Harm Than Good

A new study led by Brigham Young University (BYU) in collaboration with German research institutions has found that regular consumption of fruit juice may increase the risk of type 2 diabetes. Published in the journal JAMA Network Open, the large-scale meta-analysis concluded that each additional 230ml serving of fruit juice per day is associated with a 5% increased risk of developing type 2 diabetes. In contrast, natural sugars consumed through whole foods like fruits and dairy do not carry the same risk and may even be linked to a reduced risk of the disease.

The study analyzed data from more than 500,000 individuals across multiple countries to explore how different forms of sugar impact metabolic health. Researchers compared the effects of sugars consumed in beverages-both natural and added-to those found in whole foods. They discovered that sugar-sweetened beverages like soda had the highest impact, raising diabetes risk by 25% per 350ml serving. Fruit juice, often perceived as a healthier alternative, also contributed to an elevated risk, though to a lesser extent.

“When sugar is consumed through drinks, it rushes into the bloodstream quickly, triggering a spike in blood glucose,” the researchers explained. “This sudden overload can overwork the liver and disrupt insulin sensitivity, both red flags for type 2 diabetes.”

The key difference lies in how sugar is delivered to the body. Whole fruits come with fibre, vitamins, and antioxidants, which slow digestion and stabilize blood glucose levels. Juices, stripped of fibre, deliver concentrated sugar in liquid form, causing rapid glucose spikes. While fruit juice retains some nutrients, the absence of fibre and the high sugar concentration diminish its health benefits.

This research marks a significant shift in nutritional thinking. While fruit juice may still have a place in the diet, moderation is essential, and whole fruits remain the better choice for metabolic health.

Reference: Della Corte, K. A., Bosler, T., McClure, C., Buyken, A. E., LeCheminant, J. D., Schwingshackl, L., & Della Corte, D. (2025). Dietary Sugar Intake and Incident Type 2 Diabetes Risk: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies. Advances in Nutrition, 100413.