Extreme temperatures increase risk of heart failure deaths

According to a new study performed, exposure to extremely hot or cold temperatures raises a heart disease patient’s risk of dying.

This graph shows temperature percentiles and relative risk (RR) of dying from heart disease in 567 cities worldwide. The dashed line represents the temperature associated with lowest risk of death. The dotted lines represent the 1st percentile (extreme cold) and the 99th percentile (extreme heat). Image Credit: Circulation

The study has been recently reported in the American Heart Association’s journal Circulation.

The worldwide analysis of over 32 million cardiovascular deaths over four decades reported a high number of deaths on days when temperatures were at their highest or lowest compared to moderate climate days.

It underscores the urgent need to develop measures that will help our society mitigate the impact of climate change on cardiovascular disease."

Haitham Khraishah, MD, Study Co-Author and Cardiovascular Disease Fellow, School of Medicine, University of Maryland

Among the kinds of cardiovascular disease, people with heart failure were most likely to be negatively affected by very cold and very hot days, facing a 12% higher risk of dying on extreme heat days than optimal temperature days in a particular city. The extreme cold raised the threat of heart failure deaths by 37%.

The outcomes were dependent on an analysis of health data from over 32 million cardiovascular deaths that happened in 567 cities in 27 countries on 5 continents between 1979 and 2019. The explanation of extreme weather varied from city to city.

It was specified as the top 1% or bottom 1% of the so-called, “minimum mortality temperature,” which is the temperature at which the lowest death rate has been obtained.

For every 1,000 cardiovascular deaths, the researchers found that:

• Extreme hot days (above 86 °F in Baltimore) are available for 2.2 extra deaths.
• Extreme cold days (below 20 °F in Baltimore) reported 9.1 additional deaths.
• Of the kinds of heart diseases, the highest number of extra deaths was discovered for people with heart failure (2.6 extra deaths on extremely hot days and 12.8 on extremely cold days).

While we do not know the reason why temperature effects were more pronounced with heart failure patients it could be due to the progressive nature of heart failure as a disease. One out of four people with heart failure are readmitted to the hospital within 30 days of discharge, and only 20 percent of patients with heart failure survive 10 years after diagnosis."

Haitham Khraishah, MD, Study Co-Author and Cardiovascular Disease Fellow, School of Medicine, University of Maryland

Climate change has been discovered to result in weather extremes on both ends of the spectrum. A 2021 study published in the journal Science has discovered that Arctic warming made a change of events resulting in an interruption of the polar vortex making periods of extreme cold in the Northern hemisphere.

Barrak Alahmad, MD, Ph.D., research fellow at the Harvard T.H. Chan School of Public Health at Harvard University in Boston and a faculty member at the College of Public Health at Kuwait University in Kuwait City, was the study’s corresponding author.

Dr. Khraishah and Dr. Alahmad made a measure over the last four years to construct the heart disease mortality database for this study with collaborators from over 35 institutions globally.

The team made and extended the heart disease mortality database as part of the Multi-Country Multi-City (MCC) Collaborative Research Network. This is known as a consortium of biostatisticians, epidemiologists, and climate scientists learning the health effects of climate and associated environmental stressors on death rates.

This study provides an indisputable link between extreme temperatures and heart disease mortality from one of the largest multinational datasets ever assembled. The data can be more deeply mined to learn more about the role of health disparities and genetic predispositions that make some populations more vulnerable to climate change."

Mark T. Gladwin, MD, Dean, School of Medicine, University of Maryland

Also, Gladwin is the Vice President for Medical Affairs, at the University of Maryland, Baltimore, and the John Z. and Akiko K. Bowers Distinguished Professor.

According to Dr. Khraishah, such questions will be answered in research that will occur in the future.

A few restrictions of the study consist of the underrepresentation of data from South Asia, the Middle East, and Africa. 

The scientists also considered humidity and air pollutants, which could have accounted for surplus deaths in places with temperature extremes. Also, they regulated the delayed effect of temperature on climate zones and human health (lag effect).

“This landmark paper is a call to view climate change as a growing public health concern and highlights the need to investigate it as a potential cause of health disparities,” stated Stephen N. Davis, MBBS, Chair of the Department of Medicine at UMSOM and Physician-in-Chief at UMMC.

This study was financially supported by the Kuwait Foundation for the Advancement of Science.