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Here are the top health news for the day:
Human Heat Tolerance Lower Than Previously Believed: Study Finds
A study from the University of Ottawa’s Human and Environmental Physiology Research Unit (HEPRU) has confirmed that the limits for human thermoregulation are lower than previously thought. The findings are published in Proceedings of the National Academy of Sciences.
The research highlights the urgent need to address the impacts of climate change on human health. The study found that many regions may soon experience heat and humidity levels that exceed the safe limits for human survival.
Utilizing a widely used technique known as thermal-step protocols, researchers exposed 12 volunteers to various heat and humidity conditions to identify the point at which thermoregulation becomes impossible. Participants were subjected to extreme conditions, 42°C with 57% humidity, representing a humidex of approximately 62°C. “The results were clear. The participants’ core temperature streamed upwards unabated, and many participants were unable to finish the 9-hour exposure. These data provide the first direct validation of thermal step protocols, which have been used to estimate upper limits for thermoregulation for nearly 50 years”, says Meade former Senior Postdoctoral Fellow Ottawa's Faculty of Health Sciences.
Reference: R.D. Meade, F.K. O’Connor, B.J. Richards, E.J. Tetzlaff, K.E. Wagar, R.C. Harris-Mostert, T. Egube, J.J. McCormick, & G.P. Kenny, Validating new limits for human thermoregulation, Proc. Natl. Acad. Sci. U.S.A. 122 (14) e2421281122, https://doi.org/10.1073/pnas.2421281122 (2025).
Trial Shows Tirzepatide May Benefit People with Obesity, Kidney Disease and Heart Failure
The drug tirzepatide improved kidney function and cardiovascular outcomes among patients with obesity and heart failure with preserved ejection fraction (HFpEF) compared with placebo at one year, according to study published in Journal of the American College of Cardiology. The overall rate of cardiovascular death or worsening heart failure, the trial’s primary endpoint, was higher in the 60% of study participants who also had chronic kidney disease. However, tirzepatide reduced the risk of the primary endpoint to a similar degree in patients with and without kidney disease.
In the new analysis of data from the SUMMIT trial, researchers focused on patients with obesity, chronic kidney disease and heart failure with preserved ejection fraction because they commonly have interacting root causes and are associated with poor outcomes, indicating a significant unmet need.
The SUMMIT trial enrolled 731 patients with heart failure with preserved ejection fraction and a body mass index of 30 m2/kg or higher. About 60% of the study participants also had chronic kidney disease. Half were randomly assigned to receive tirzepatide and half received a placebo. Neither patients nor their clinicians were aware of which regimen they had been assigned.
At one year, patients taking tirzepatide had a 38% lower rate of cardiovascular death or worsening heart failure compared with the placebo group.
The researchers used two strategies for assessing kidney function, measuring creatinine and cystatin C at 12, 24 and 52 weeks. Ultimately, participants taking tirzepatide showed significant improvements over those taking placebo in terms of both markers of kidney function, although the results showed different patterns over time and among different patient groups.
Reference: Packer, M, Zile, M, Kramer, C. et al. Interplay of Chronic Kidney Disease and the Effects of Tirzepatide in Patients With Heart Failure, Preserved Ejection Fraction, and Obesity: The SUMMIT Trial. JACC. null2025, 0 (0).
https://doi.org/10.1016/j.jacc.2025.03.009
Rural Residents Face Higher Heart Health Risks Than Urban Residents: Study
A new study has found adults living in rural areas were more likely than those living in large cities to have heart disease, high blood pressure, high cholesterol, obesity, and diabetes. Across all age groups, the differences in high blood pressure, obesity, and diabetes were largest among adults ages 20–39 living in rural areas vs. cities.
Investigators reviewed data from more than 27,000 adults who participated in the 2022 National Health Interview Survey to understand geographical differences in rates of heart disease and risk factors for conditions that affect the heart and blood vessels, such as high blood pressure, diabetes, and obesity.
They found that factors such as levels of income and education, having enough food to eat, and owning a home mostly explained the higher rates of people in rural areas who had high blood pressure, diabetes, and heart disease.
The researchers also found that rates of high blood pressure, high cholesterol, diabetes, and heart disease were largest in rural areas compared to cities in the South. Rates of obesity were higher across rural areas throughout the U.S., especially in the Northeast.
Identifying factors driving the higher burden of heart disease and risk factors in rural regions remains a critical research priority. The authors note that insights from their study could inform public health efforts and policies to support and improve the cardiovascular health of people — especially younger adults — living in rural areas.
Reference: Liu M, Marinacci LX, Joynt Maddox KE, Wadhera RK. Cardiovascular Health Among Rural and Urban US Adults—Healthcare, Lifestyle, and Social Factors. JAMA Cardiology. Published online March 31, 2025. doi:10.1001/jamacardio.2025.0538
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