Global warming predicted to adversely affect crop production and increase undernutrition: study

Xu et al (2019) undertook the Brazil-based study with the aim of understanding and quantifying the correlation between short-term heat exposure and the risk of hospitalization from undernutrition.

First of its kind to analyze heat exposure and hospitalization​

Hailed as “the first study to our knowledge to evaluate the association between heat exposure and risk of hospitalization for undernutrition”​, the study looks at the effects of heat exposure on the hospitalization of people with existing malnutrition.

It also explores whether this connection is consistent across different types of undernutrition and population demographics, including age, sex, and various regions in the Latin American country. Then, the research anticipates the number of all undernutrition hospitalizations that are directly associated with heat exposure.

The researchers of this study used a time-stratified case-crossover design, using a national hospitalization dataset obtained from the Brazilian Unified Health System (BUHS). Daily hospitalization data was present for almost 80% of the Brazilian population during 2000−2015.

The study analyzed multiple regions including North, Northeast, Central West, and Southeast, geographically, covering nearly 80% of the Brazilian population.

Defined as an “inadequate intake of energy and nutrients to meet an individual’s needs to maintain good health”​ (Maleta, 2006), undernutrition has been under the microscope for decades and although has seen significant progress, still remains a public health concern around the world.

Global warming risks​

Global warming has been identified as an indirect precursor to higher levels of undernutrition due to the potentially detrimental impact on crop yields and food security over the long-term.

However, it was unknown whether rises in temperature could directly affect nutrition as no study had analyzed the short-term and direct effect of heat exposure on morbidity associated with undernutrition.

Collecting hospitalization and weather data for the hot season from a total of 1,814 Brazilian cities during 1 January 2000−31 December 2015, researchers found a 2.5% increase in undernutrition hospitalizations after every 1°C increase in daily mean temperature during the hot season.

By examining the connection between heat exposure and hospitalization, the study shows how rising temperatures might affect increasing levels of undernutrition morbidity both directly and faster than through threatening food security alone.

Heat may directly impact people by lowering undernourished individuals’ food intake, damaging their ability to digest and absorb food, and disturbing fluid and electrolyte functioning.

At-risk population​

During the 2000-2015 hot seasons, 238,320 hospitalizations for undernutrition were recorded, with estimations that 15.6% (37,129 cases) of undernutrition hospitalizations could be linked back to heat exposure.

Demographically, young people (aged between 0-19 years) and elderly people (those 80 years old and over) were found to be more vulnerable to heat exposure than other groups.  Over 25% of hospital admissions for undernutrition were linked to heat exposure in these age categories.

The findings in Brazil, between 2000 and 2015, is a warning about the effects of global warming, and how, its ramifications can be experienced both directly and in the short-term. Due to the prevalence of global warming, awareness of the impact of heat exposure is considered vital in the future.

As the study identifies how heat exposure is associated with the heightened risk of hospitalization for undernutrition — particularly in children, adolescents and the elderly — it presents the opportunity for enhanced international strategies.

“Global strategies addressing the syndemic of climate change and undernutrition should focus not only on food systems but also on the prevention of heat exposure, especially among the young and elderly,” ​the study states.

Direct and short-term implications​

The misclassification of various forms of undernutrition is a key limitation attached to the study, suggesting the importance of clear and consistent identification and understanding of undernutrition that is supported by educational initiatives and communication efforts. 

Along with the availability of a large sample size, there are several success indicators championing the strength of the study’s results in Brazil. The Latin American country is both large and considerable in terms of its variations in temperature, which suggests the data could be extrapolated to other countries with similar climates.

As Brazil is also one of the largest middle-income countries, the results may also have implications for other large middle-income nations across the globe.

Source: PLoS Med​
16(10): e1002950. Accessed at: https://doi.org/10.1371/journal.pmed.1002950​
“​​The association between heat exposure and hospitalization for undernutrition in Brazil during 2000−2015: A nationwide case-crossover study​”​
Authors: R. Xu et al.