Global warming's threat to health

Monash University researchers warn that global warming is likely to increase illnesses caused by undernutrition, due to the effects of heat exposure.

It is well documented that global temperature rises will indirectly result in more undernourished people through threatened crop production and increased food insecurity, but what about the short-term and direct impact of heat exposure on undernutrition?

In a 15-year study, a team of researchers from Monash University investigated the relationship between short-term heat exposure and risk of hospitalisation due to undernutrition in Brazil. Led by Yuming Guo, Associate Professor of Environmental Epidemiology and Biostatistics in the School of Public Health and Preventive Medicine, the researchers analysed daily hospitalisation data covering almost 80% of Brazil between 2000 and 2015.

The link between daily mean temperatures and hospitalisation for undernourishment was studied according to the International Classification of Diseases. The researchers found that for every 1°C increase in daily mean temperature during the hot season, there was a 2.5% increase in the number of hospitalisations for undernutrition.

The researchers found that the association between increased heat and hospitalisation for undernutrition was greatest for individuals aged over 80 years and those aged 5–19 years, with 15.6% of undernutrition hospitalisations attributed to heat exposure during the study period.

The study, published in PLOS Medicine, highlights the growing problem of undernutrition as a result of global warming.

“Climate change is one of the biggest threats to the reduction of hunger and undernutrition, especially in low- and middle-income countries. It has been estimated that climate change will reduce global food availability by 3.2% and thus cause about 30,000 underweight-related deaths by 2050,” the report said.

“However, this may actually underestimate the real effect of climate change on future undernutrition-related morbidity and mortality, because it overlooks the direct and short-term effects of temperature rise.

“We estimated that over 15% of undernutrition hospitalisations could have been attributable to heat exposure in Brazil during the study period.”

How does increased heat cause illness via undernourishment

The study suggested that increased heat may cause illness through undernourishment in a number of ways:

• Reducing appetites.
• Provoking more alcohol consumption.
• Reducing motivation or ability to shop and cook.
• Exacerbating any undernutrition, resulting in hospitalisation.
• Worsening a person’s already impaired digestion and absorption by increasing gastrointestinal morbidity.
• Impairing thermoregulation.
   

“It is plausible to speculate that climate changes could not only increase the rate of undernutrition in the most affected areas of the globe, but at the same time, impair individuals’ capacity to adapt to projected rises in temperature,” the researchers said.

“Global strategies addressing the syndemic of climate change and undernutrition should focus on food systems, but also on the prevention of heat exposure.”

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