Researchers from Helmholtz Munich and the Augsburg University Hospital in Germany found that the risk of stroke among older women is seven per cent higher on warm nights.

As the march of climate change continues, notwithstanding the many climate accords aimed at arresting the progress of global warming, a recent study has added to the list of adverse effects of climate change on human health. The study titled ‘Nocturnal heat exposure and stroke risk’, published in the European Heart Journal, establishes a positive correlation between high temperatures and the risk of stroke, particularly among older women. 

In the study, researchers from Helmholtz Munich and the Augsburg University Hospital in Germany found that the risk of stroke among elderly women increases with rise in ambient night-time temperatures. This risk is seven per cent higher on warm nights. Climate change causes night-time temperatures to rise much faster than day-time temperatures. 

Data was collected from 11,000 episodes of strokes over a 15-year period. From 2006 to 2012, hot nights led to two additional strokes per year in the study group, whereas, the 2013 to 2020 period, witnessed 33 additional cases per year. Of these, majority cases pertained to ischemic strokes, wherein there is a sudden loss of blood circulation to an area of the brain, leading to corresponding loss of neurologic function. 

Other cases of stroke pertained to bleeding in the brain, referred to as haemorrhagic stroke. Furthermore, elderly individuals, women and patients with mild stroke symptoms exhibited significantly increased vulnerability to nocturnal heat. The observations attest to the importance of factoring night-time ambient heat as a critical parameter in addressing stroke risks in excessively warm surroundings.

During periods of extreme heat, one is at a risk of dehydration. One’s cardiovascular system is able to offset the likely loss of water content from one’s body by releasing a hormone called vasopressin, released by the body to restrict the amount of urine release and to constrict the small blood vessels. Consequently, the heart has to work harder to circulate blood resulting in excessive load on the heart and a subsequent hypertensive condition, or hypertension. A regular hypertensive condition could result in a heart attack or stroke. The likelihood of an ischemic or hemorrhagic stroke significantly increases during bouts of hypertension in humid surroundings.  

Given that the average age of the study cohort was 70 years, some experts have raised concerns about the difficulty to discern whether the cause of stroke was the ambient heat or other age-related complications. However, it’s advisable to maintain cool ambient conditions and adequately hydrate oneself during the day and nighttime, more so for elderly women. 

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