Changes in temperature have predictable effects on human physiology. Exposure to hot temperatures changes heart rate and the coagulability of blood while exposure to cold temperatures contributes to a rise in blood pressure and serum cholesterol levels.
Past research has shown that fluctuations in temperature can increase the frequency of heart attacks (myocardial infarction) in temperate settings. Cold exposure, heat exposure, and heat waves in temperate settings are all shown to increase the risk of myocardial infarction.
In tropical climates, thermal amplitudes tend to be narrower, meaning there is less variation in temperature between seasons. With these differences in mind, researchers wanted to determine whether a similar trend between weather fluctuations and increased risk of heart attack exists in tropical climates as well. The researchers used data from the Singapore Myocardial Infarction Registry that was collected in Singapore over the course of 10 years. In total, 60,643 reports were used in this study.
The researchers found that a drop of just 1°C in ambient temperature increased the risk of a type of acute myocardial infarction in the population by 12%. People over the age of 65 were 20% more vulnerable to these temperature fluctuations.
Dr. Andrew Ho, one of the study’s first authors, says that “even in a relatively warm part of the world, cooler ambient temperatures increased the risk of heart attacks. This improves our understanding that deviations from the temperature that one is used to can lead to harmful bodily stress.”
These results are significant as weather fluctuations and extreme weather events are expected to become more common as climate change worsens in the tropics. These findings could impact public health recommendations for those in tropical climates.
“There are several individual-level risk factors for cardiovascular disease, but none are as widely experienced as weather patterns,” says Dr. Joel Aik, co-senior author of the study. “Daily weather variations have the capacity to trigger cardiovascular disease events in at-risk individuals. In the context of climate change, these findings highlight a risk factor of substantial public health concern.”