New Delhi: The impact of climate change on increased heatwaves and all-round mortality has been studied before, but a new study in journal Nature Communications looks specifically at how extreme temperatures caused by climate change leads to neonatal deaths in low- and middle-income countries (LMICs). An analysis by researchers from Postdam Institute of Climate Impact Research, a global think-tank based in Germany, found that between 2001-2019, 4.3 percent of the all babies that died across 29 countries within the first month of their birth died due to temperature-related anomalies.
The study, published on 29 June, found that Pakistan, Sierra Leone and Mali — which have the highest neonatal mortality rates of all countries studied — were also the countries with the highest neonatal mortality caused by temperature anomalies.
This is one of the first studies that looks at the impact of ambient temperatures on neonatal mortality in LMICs in tropical environments like South Asia or in sub-Saharan Africa. The researchers are also the first to look at the effect of climate change on the temperature-related neonatal deaths, and they found that 32 percent of the heat-related neonatal deaths in the 29 countries, including India, were due to climate change. Since neonates are impacted by both extremely high and extremely low temperatures, the study also found that cold-related neonatal deaths in the same period were reduced by 30 percent due to climate change.
The sample size of neonatal deaths used in the study was 40,073. However, the data was taken from the Demographic and Health Survey, which is the “largest international dataset on neonatal deaths in LMICs”. The results were then applied to the general population in these countries, taking into account country-specific temperature ranges and population size. While discussing the findings of their analysis towards the end, the authors said that this study calls for mitigation and adaptation measures for public health being affected by climate change.
A report by global non-profit group Climate Central on 28 June had said around 5 billion people in the world faced climate change-related extreme heat in 9 days in June. The highest number was in India, but the list also included other LMICs like Bangladesh, Ethiopia and Nigeria, each with more than 100 million people suffering from heat waves in June 2024.
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How is climate impact on deaths calculated?
There have been studies previously conducted that show how temperature imbalance can affect neonatal and even prenatal mortality, because their bodily systems are just too vulnerable. They have a lower optimal body temperature than adults, and their body’s temperature regulation system is also much weaker.
The Nature study was conducted building on this research on extreme heat/cold and effects on neonatal health. Additionally, the researchers made a distinction between newborn deaths in the first 24 hours of life (very early neonatal deaths) and in the first month of life (neonatal deaths) since the exposure pathways are different for both.
This research was conducted on two levels — first to calculate the relationship between ambient temperature, i.e. the atmospheric temperature, and neonatal mortality, and second to quantify how much of the change in ambient temperature was due to climate change.
In the first stage, they used a statistical method called a time-stratified case-crossover analysis which is basically measuring the impact of changing conditions (in this case weather) on acute events (neonatal mortality).
The analysis showed that lower temperatures were linked with higher overall neonatal mortality, but higher ambient temperatures led to higher very early neonatal mortality i.e. babies in the first 24 hours of life.
In the second part of the study, they used something called an impact attribution study, to isolate the impact of human-induced climate change on ambient temperatures as opposed to other factors.
They used two different temperature datasets — one factual with real-time warming across 10 years and another counterfactual without the excess warming attributable to climate change — to calculate the risk of neonatal mortality at each temperature level.
The study then assessed the number of neonatal deaths specifically due to climate change-induced temperature changes by subtracting the mortality number of the counterfactual dataset from the factual dataset.
After this they were able to calculate how many heat-specific and cold-specific neonatal deaths had occurred due to climate change.
India’s neonatal mortality rate is around 3,200 deaths per 100,000 births, marginally higher than Bangladesh and Nepal’s mortality rates. Less than 15 percent of heat-related neonatal deaths in India were due to climate change, which is lower than the average 32 percent for the entire dataset. It is also lower than Nepal and Bangladesh, where the number was 15-20 percent. Reduction of cold-related deaths due to climate change, too, were minimal in India, lingering in the 0-15 percent range, similar to its neighboring countries.
The highest rates of temperature-related neonatal mortality were in the countries with the highest overall neonatal mortality rates, namely Pakistan, Sierra Leone and Mali. Philippines, Haiti and Rwanda, on the other hand, saw the highest contribution of climate-change-related heat to neonatal deaths.
The study also measured that in the same time period of 2001-2019, the number of cold-related neonatal deaths were reduced by 30 percent overall due to climate change-induced temperature levels. While this was seen as a gain in the study period, the authors warned that as the average global temperature rises, these gains are expected to reduce, and heat-related neonatal mortality is projected to increase.
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