Extreme heat may pose the greatest climate change risk to child health by increasing the likelihood of preterm birthResearch shows that children are more susceptible than adults to climate change-related health risks. Although research is increasingly examining the health impacts of climate change on children, studies assessing the magnitude of these effects remain scarce. To address this gap, this systematic review and meta-analysis aimed to identify which climate-health relationships pose the greatest risks to children. This review and meta-analysis is the first to compare the relative risk of specific health outcomes across multiple climate variables. The study was guided by the question: “Which climate variables pose the greatest disease burden for children?”
A systematic search of the published literature was conducted to identify peer-reviewed studies examining children’s (age 0–18) exposure to climate extremes or climate change events and physical health outcomes. The search aimed to include a wide range of climate variables and health outcomes to provide a broad overview of research and identify all available data for the meta-analysis. No restrictions were placed on the year of study publication; however, only studies published in English, Indonesian, or Dutch were considered for inclusion. The search yielded 163 studies that examined climate variables and children’s health outcomes. The studies’ methodologies varied considerably, and a risk of bias assessment was conducted for each included study. The meta-analysis quantitatively examined findings across studies. To enable quantitative synthesis, the researchers standardized health outcome reporting metrics when feasible. Studies that did not provide sufficient data were excluded from the meta-analysis. Most studies included in the meta-analysis focused on populations in the Northern Hemisphere (84.5%). The majority of these studies were conducted in high-income (56%) and upper-middle-income (39%) nations or regions. Very few were conducted in lower-middle-income (2%) or low-income (2%) nations or regions.
The review found that the examined health domains focused on morbidity/mortality and perinatal and respiratory outcomes. Thirty-three studies focused on morbidity or mortality, mainly due to exposure to extreme temperatures. Results indicated that exposure to extreme or increased temperatures raised the risk of emergency department visits and hospital admissions. This was particularly true among low socio-economic status populations, where children in low- and middle-income cities were at a heightened risk of hospitalization compared to high-income cities. Exposure to extreme cold and extreme heat was also linked to an increased risk of all-cause mortality. Young children (under 5 years) faced the highest risk from high temperatures. Perinatal outcomes were examined in 49 studies, including 39 focused on the impact of temperature changes and 10 on air pollutants. In general, temperature studies reported that exposure to extreme heat or cold increased preterm birth risk. The risks of preterm birth generally increased with increasingly extreme high temperatures, although there was some variation between studies. Extreme heat exposure was also linked to an increased risk of low birth weight, although findings were somewhat mixed. Most studies examining airborne pollutants linked poor air quality to increased risk of preterm birth and low birth weight. One study reported that air pollution was related to an increased risk of stillbirth. Respiratory outcomes were investigated by 43 studies. These studies found that cold extremes and temperature fluctuations were linked to increased respiratory diseases, emergency department visits, and hospital admissions. Studies exploring the relationship between air quality and childhood respiratory health found an increased risk of asthma, particularly from fire smoke, although there was some variation across studies. Increasing airborne pollutants were also associated with increased respiratory disease, hospitalizations among children with asthma, and a greater risk of childhood asthma.
The meta-analysis found that temperature extremes had a stronger effect on the risk of preterm birth than on the risk of respiratory disease or on mortality/morbidity. On average, exposure to temperature extremes was associated with a 60% increase in the risk of preterm birth; however, there was wide variability across studies. In fact, 8 of the 27 (30%) studies included in the meta-analysis of temperature effects did not report an association between temperatures and risk of preterm birth. Across studies, no consistent pattern emerged between the magnitude of temperature change and changes in any health outcome category. This suggests that variability in study findings resulted in a lack of discernible trends in outcomes. The meta-analysis also found that the effects of different air pollutants on health outcomes were smaller than temperature effects, but most studies (80%) reported at least a weak effect. On average, air pollution effects were slightly higher for respiratory disease than for perinatal outcomes.
Despite considerable variation and inconsistencies across studies, this review strengthens the overall evidence of the relationship between climate change exposures and adverse child health outcomes. Results suggest that temperature extremes may pose the greatest risk to child health by increasing the likelihood of preterm birth. The researchers conclude that “increased preterm birth, more respiratory disease, higher mortality, and more children in hospital are but a few of the health problems societies will face as climate change worsens.” The meta-analysis also indicates that the extent to which climate change affects child health may vary widely between countries and regions, making cross-study comparisons complex. Notably, only 4% of the studies included in the meta-analysis were conducted in lower-middle- and low-income nations/regions. This limits the generalizability of findings in these nations and highlights the need for more studies that prioritize how climate change affects child health in low-income nations. In addition, the researchers call for action to protect children from the adverse impacts of climate change, such as developing public health policies to counter climate-related disease burden.
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