Among the cardiovascular diseases examined in
a recent study, heart failure was linked to the highest excess deaths from
extreme hot and cold temperatures. New research published in the American Heart
Association’s flagship journal Circulation shows that extremely hot and cold
temperatures both increased the risk of death among people with cardiovascular
diseases, such as ischemic heart disease (heart problems caused by narrowed
heart arteries), stroke, heart failure and arrhythmia.
“The decline in cardiovascular death rates
since the 1960s is a huge public health success story as cardiologists
identified and addressed individual risk factors such as tobacco, physical
inactivity, Type 2 diabetes, high blood pressure and others. The current
challenge now is the environment and what climate change might hold for us,”
said Barrak Alahmad, M.D., M.P.H., 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.
Researchers explored how extreme temperatures
may affect heart diseases – the leading cause of death globally. They analyzed
health data for more than 32 million cardiovascular deaths that occurred in 567
cities in 27 countries on 5 continents between 1979 and 2019. The global data
came from the Multi-Country Multi-City (MCC) Collaborative Research Network, a
consortium of epidemiologists, biostatisticians and climate scientists studying
the health impacts of climate and related environmental stressors on death
rates.
Climate change is associated with substantial
swings in extreme hot and cold temperatures, so the researchers examined both
in the current study. For this analysis, researchers compared cardiovascular
deaths on the hottest and the coldest 2.5% of days for each city with
cardiovascular deaths on the days that had optimal temperature (the temperature
associated with the least rates of deaths) in the same city.
For every 1,000 cardiovascular deaths, the
researchers found that:
Extreme hot days accounted for 2.2 additional
deaths.
Extreme cold days accounted for 9.1 additional
deaths.
Of the types of heart diseases, the greatest
number of additional deaths was found for people with heart failure (2.6
additional deaths on extreme hot days and 12.8 on extreme cold days).
“One in every 100 cardiovascular deaths may be
attributed to extreme temperature days, and temperature effects were more
pronounced when looking at heart failure deaths,” said Haitham Khraishah, M.D.,
co-author of the study and a cardiovascular disease fellow at the University of
Maryland School of Medicine and the University of Maryland Medical Center in
Baltimore. “While we do not know the reason, this may be explained by the
progressive nature of heart failure as a disease, rendering patients
susceptible to temperature effects. This is an important finding since one out
of four people with heart failure are readmitted to the hospital within 30 days
of discharge, and only 20% of patients with heart failure survive 10 years
after diagnosis.”
Researchers suggest targeted warning systems
and advice for vulnerable people may be needed to prevent cardiovascular deaths
during temperature extremes.
“We need to be on top of emerging
environmental exposures. I call upon the professional cardiology organizations
to commission guidelines and scientific statements on the intersection of
extreme temperatures and cardiovascular health. In such statements, we may
provide more direction to health care professionals, as well as identify
clinical data gaps and future priorities for research,” Alahmad said.
The underrepresentation of data from South
Asia, the Middle East and Africa limits the ability to apply these findings to
make global estimates about the impact of extreme temperatures on
cardiovascular deaths.
“This study contributes important information
to the ongoing societal discussions regarding the relationship between climate
and human health. More work is needed to better define these relationships in a
world facing climate changes across the globe in the years ahead, especially as
to how those environmental changes might impact the world’s leading cause of
death and disability, heart disease,” said AHA Past President Robert A.
Harrington, M.D., FAHA, who is the Arthur L. Bloomfield Professor of Medicine
and chair of the department of medicine at Stanford University.
Reference:
Haitham Khraishah, Associations Between
Extreme Temperatures and Cardiovascular Cause-Specific Mortality: Results From
27 Countries, Circulation, DOI
10.1161/CIRCULATIONAHA.122.061832