Differential mortality risks associated with ambient temperature among migrants and non-migrants: a space-time-stratified case-crossover study of the 100 Million Brazilian Cohort (2000–2020)
6 affiliations
- 1Infectious Disease Epidemiology & International Health, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK
- 2Centro de Integração de Dados e Conhecimentos para Saúde (Cidacs), Fundação Oswaldo Cruz, Salvador, Brazil
- 3Department of Statistics, Institute of Mathematics and Statistics, Fluminense Federal University, Niterói, Brazil
- 4National Institute for Space Research (INPE), Cachoeira Paulista, Brazil
- 5Institute of Collective Health, Federal University of Bahia, Salvador, Brazil
- 6Faculty of Public Health and Policy, Department of Public Health, Environments and Society, London School of Hygiene and Tropical Medicine, London, UK
Abstract
Background: Climate change disproportionately affects socially minoritized populations, but migrants' vulnerability to extreme temperatures remains overlooked. We estimated short-term associations between extreme ambient temperatures and mortality among migrants and non-migrants across Brazil.
Methods: We linked the 100 Million Brazilian Cohort to mortality and temperature data (2000–2020) and conducted a space-time-stratified case-crossover study analysing the differential effects of extreme temperature on mortality among internal migrants (i.e., Individuals whose state of birth was different from their residence at registration or death) and non-migrants. We used conditional quasi-Poisson regression with distributed lag non-linear model (DLNM) to estimate relative risks (RRs) and 95% confidence intervals (CIs) for all-cause non-accidental and cause-specific mortality associated with extreme-cold (1st percentile) and extreme-heat (99th percentile) compared to minimum-mortality-temperature (i.e., the temperature associated with the lowest mortality risk), over 0–20 days in both groups. We further stratified by age, literacy, urbanicity and housing conditions.
Findings: We included 1,199,636 deaths among internal-migrants (mean age at death = 62.67 years (standard-deviation (SD) = 18.36), with 673,166 (56%) males) and 3,716,900 deaths among non-migrants (57.18 years (SD = 20.31), with 2,135,293 (57%) males). Over 0–20 days, we observed a consistent pattern of higher risks of all-cause, non-accidental mortality among internal-migrants than non-migrants following both extreme-heat (RRMig(95%CI):1.05(1.01–1.10) vs. RRNon-mig:1.01(0.99–1.04)) and extreme-cold (RRMig:1.27(1.22–1.32) vs. RRNon-mig:1.24(1.20–1.28)). Extreme cold-related circulatory mortality (mortality due to diseases of the circulatory system, based on the relevant International Classification of Diseases codes) (I00–I99) was higher among non-migrants (RRMig:1.32(1.20–1.45) vs. RRNon-mig:1.41(1.31–1.51)) while heat-related respiratory mortality (J00–J99) was higher among internal-migrants (RRMig:1.32(1.10–1.58) vs. RRNon-mig:1.06(1.00–1.17)), particularly those illiterate (RRMig:1.84(1.25–2.71) vs. RRNon-mig:1.10(0.89–1.36)). Other subcategories showed greater 95%CI overlap.
Interpretation: We found internal migrants are likely to experience higher heat-related respiratory mortality than non-migrants particularly low-educated migrants. Our results highlight the need to further consider migrants for targeted climate adaptation policies, with a focus on reducing social inequalities in the place of arrival.
Funding: The Wellcome Trust.
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BibTeX
@article{firouraghi2026differential,
title = {{Differential mortality risks associated with ambient temperature among migrants and non-migrants: a space-time-stratified case-crossover study of the 100 Million Brazilian Cohort (2000–2020)}},
author = {Neda Firouraghi and Taisa R. Cortes and Ludmilla V. Jacobson and Danielson J.D. Neves and Ismael H. Silveira and Shakoor Hajat and Mauricio L. Barreto and Julia M. Pescarini},
journal = {Lancet Regional Health - Americas},
year = {2026},
month = oct,
doi = {10.1016/j.lana.2026.101687},
url = {https://doi.org/10.1016/j.lana.2026.101687},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Differential mortality risks associated with ambient temperature among migrants and non-migrants: a space-time-stratified case-crossover study of the 100 Million Brazilian Cohort (2000–2020)
AU - Neda Firouraghi
AU - Taisa R. Cortes
AU - Ludmilla V. Jacobson
AU - Danielson J.D. Neves
AU - Ismael H. Silveira
AU - Shakoor Hajat
AU - Mauricio L. Barreto
AU - Julia M. Pescarini
PY - 2026
DA - 2026/10/27
JO - Lancet Regional Health - Americas
DO - 10.1016/j.lana.2026.101687
UR - https://doi.org/10.1016/j.lana.2026.101687
AB - Background: Climate change disproportionately affects socially minoritized populations, but migrants' vulnerability to extreme temperatures remains overlooked. We estimated short-term associations between extreme ambient temperatures and mortality among migrants and non-migrants across Brazil. Methods: We linked the 100 Million Brazilian Cohort to mortality and temperature data (2000–2020) and conducted a space-time-stratified case-crossover study analysing the differential effects of extreme temperature on mortality among internal migrants (i.e., Individuals whose state of birth was different from their residence at registration or death) and non-migrants. We used conditional quasi-Poisson regression with distributed lag non-linear model (DLNM) to estimate relative risks (RRs) and 95% confidence intervals (CIs) for all-cause non-accidental and cause-specific mortality associated with extreme-cold (1st percentile) and extreme-heat (99th percentile) compared to minimum-mortality-temperature (i.e., the temperature associated with the lowest mortality risk), over 0–20 days in both groups. We further stratified by age, literacy, urbanicity and housing conditions. Findings: We included 1,199,636 deaths among internal-migrants (mean age at death = 62.67 years (standard-deviation (SD) = 18.36), with 673,166 (56%) males) and 3,716,900 deaths among non-migrants (57.18 years (SD = 20.31), with 2,135,293 (57%) males). Over 0–20 days, we observed a consistent pattern of higher risks of all-cause, non-accidental mortality among internal-migrants than non-migrants following both extreme-heat (RRMig(95%CI):1.05(1.01–1.10) vs. RRNon-mig:1.01(0.99–1.04)) and extreme-cold (RRMig:1.27(1.22–1.32) vs. RRNon-mig:1.24(1.20–1.28)). Extreme cold-related circulatory mortality (mortality due to diseases of the circulatory system, based on the relevant International Classification of Diseases codes) (I00–I99) was higher among non-migrants (RRMig:1.32(1.20–1.45) vs. RRNon-mig:1.41(1.31–1.51)) while heat-related respiratory mortality (J00–J99) was higher among internal-migrants (RRMig:1.32(1.10–1.58) vs. RRNon-mig:1.06(1.00–1.17)), particularly those illiterate (RRMig:1.84(1.25–2.71) vs. RRNon-mig:1.10(0.89–1.36)). Other subcategories showed greater 95%CI overlap. Interpretation: We found internal migrants are likely to experience higher heat-related respiratory mortality than non-migrants particularly low-educated migrants. Our results highlight the need to further consider migrants for targeted climate adaptation policies, with a focus on reducing social inequalities in the place of arrival. Funding: The Wellcome Trust.
SN - 2667-193X
ER -