Our hearts are sensitive to changes in weather. Adding more evidence to this link, researchers have made a remarkable discovery about the effects of short-term cold exposure on heart health. Even a small drop in temperature, with just one unit over two to six days, can increase the risk of a heart attack by up to 11%, a recent study revealed.

In the latest study published in the JACC Journals, the researchers examined the short-term effects of lower air temperature and cold spells on the risk of hospitalization for various types of myocardial infarction among 120,380 individuals from the SWEDEHEART registry in Sweden.

The researchers then found that a brief decrease in temperature by just 1 unit over 2 to 6 days was associated with a significant rise in heart attack rates: a total increase of about 10% for all types of heart attacks, an 11% increase for non-ST-elevation myocardial infarctions (NSTEMI), and an 8% increase for ST-elevation myocardial infarctions (STEMI).

The study also revealed that when there were cold spells or a rapid drop in temperature over the same 2 to 6-day period, the risk of total heart attacks increased by about 8%. Meanwhile, NSTEMI risk increased by about 7%, and STEMI risk increased by about 10%.

Cold spells were defined as periods of at least two consecutive days where the average daily temperature was colder than the 10th percentile of temperatures recorded during the study.

"This nationwide study reveals that short-term exposures to lower air temperature and cold spells are associated with an increased risk of myocardial infarction (MI) hospitalization after two -six days, suggesting that individuals may be particularly vulnerable to acute cardiac events during periods of cold stress," said Wenli Ni, the lead author of the study in a news release.

Researchers also found that exposure on days zero to one reduced the risk of heart attack hospitalizations, likely due to people staying indoors or delaying healthcare during cold weather. However, these behaviors are temporary and might contribute to the increased hospitalizations two to six days later.

The findings not only reveal a crucial link between cold weather exposure and heart attack risk but indicate the delayed effect that peaks days after the cold spell, according to JACC Editor-in-Chief Dr. Harlan M. Krumholz.

"These findings also underscore the urgent need for targeted interventions to protect vulnerable populations during and, particularly, after cold stress," Dr. Krumholz said.

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