Extreme Temperatures, Hot Nights Associated With 7% Higher Stroke Risk, Study Reveals

A new study discovered that stroke risk was 7% higher during hot nights, especially among elderly women.

The study highlights that nocturnal heat could be a crucial trigger of stroke amidst a warming climate.

Hot Nights, Stroke Risk

The study noted that with the progression of climate change, it is crucial to know more about how it could affect human health and well-being.

As part of the new "Nocturnal heat exposure and stroke risk" study, researchers examined data of patients from Augsburg Hospital over the course of 15 years. They observed that 11,037 strokes were diagnosed from 2006 to 2020, from May up until October, which were the warmest months.

The stroke patients had an average age of 71.3 years.

The study recorded ischemic stroke as the most prevalent type, accounting for 7,430 cases. There were also 2,947 transient ischemic attacks as well as 642 hemorrhagic strokes.

The majority of strokes covered in the study included moderate-severity or minor strokes, taking up 85% of cases.

To examine the possible link between stroke and hotter nights, the scientists examined data from a meteorological station that documented conditions by the hour. These included relative humidity, temperature, and barometric pressure.

In order to reduce the effects of daytime temperature on nighttime stroke effects, they also controlled for the former.

The scientists were able to observe a minimal increase in hot-night stroke events from 2013 to 2020, as compared to 2006 to 2012.

The study also found that those who were vulnerable to the heat during the night were older individuals, especially women, and individuals who exhibited mild symptoms of stroke.

Cardiologist Cheng-Han Chen, MD from Saddleback Medical Center, who did not participate in the study, said that the findings are concerning but not surprising. It is known from earlier studies that heat-elevated temperatures that are extreme may increase cardiovascular events, such as strokes and heart attacks.

Cardiologist Jayne Morgan, MD, who is the Executive Director of Piedmont Healthcare Corporation's Health and Community Education, said that because there is a link between more heart attacks and extremely hot conditions, a similar correlation involving strokes would not be surprising. However, this does not imply causality.

Morgan also added that since the study used a homogenous population, it remains unclear whether this could apply to global diversity.

Morgan also noted that since the study's participants had an average age of 70, it is hard to conclude if the strokes were more age-related or heat-related.

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Heat and the Cardiovascular System

Chen notes that the cardiovascular system plays a huge role in thermoregulation, which is the body's temperature control. When extreme heat is present, it could affect how the cardiovascular system regulates body temperature. This, in turn, stresses the system.

Morgan also explained that dehydration due to heat could stress the body and heart. Too much sweating could also result in electrolyte imbalances.

Chen also added that heat could impact the constriction and dilation of blood vessels. Hence, such effects may potentially lead to stroke and heart attack.

Morgan added that resultantly, extreme heat can lead to increases in blood pressure. It may even heighten blood coagulability. Moreover, individuals who have pre-existing conditions could have higher susceptibility.

Both Morgan and Chen stress how important it is to be well-hydrated during hot days and hot nights. Chen also recommends having optimal circulation in one's room and keeping the windows open for sweat to evaporate.

Morgan also said that cool showers and baths and cool cloths on the skin could help reduce body temperature.