Extreme heat exposure in the first 1000 days: Implications for childhood stunting in Bangladesh

Objectives: Stunting is a critical public health issue in Bangladesh, a country highly vulnerable to climate change and increased extreme heat exposure. Limited research has examined the relationship between extreme heat during the first 1000 days of life and stunting. This study provides the first evidence from Bangladesh on the likelihood of stunting among children aged 24-59 months following exposure to extreme heat during this crucial developmental period. Study design: The study utilized district-level panel data from the 2012 and 2019 Multiple Indicator Cluster Surveys, comprising of 24,035 children aged 24-59 months, paired with daily temperature records reflecting conditions from the child's firth 1000 days. Methods: A multilevel logistic regression model with district-level random effects assessed the relationship between extreme heat exposure and stunting. Results: A 1 % increase in extreme heat days during the first 1000 days of life was associated with higher odds of stunting (adjusted odds ratio [AOR] 1.56, 95 % confidence interval [CI] 1.25-1.95, p < 0.0001) at 24-59 months of age. Post-birth exposure to extreme heat showed a stronger association with stunting (AOR 1.67, 95 % CI 1.37-2.03, p = 0.063) than in utero exposure (AOR 1.28, 95 % CI 1.14-1.44, p < 0.0001). Conclusion: Escalating extreme heat threatens decades of progress in reducing stunting in Bangladesh. Mitigation efforts targeting the first 1000 days of life are critical, alongside further research to disentangle the specific effects of extreme heat on child growth within the broader context of climate change.