The impact of extreme temperatures on respiratory mortality in Brazil: evaluating regional adaptations to different thermal environments

We conducted a nationwide ecological time-series study to quantify the association between ambient temperature and respiratory mortality across Brazil's diverse climates. Using data from 520 municipalities (population ≥50,000) from 2010 to 2020, we analysed 1,008,157 respiratory deaths (ICD-10 J00–J99) using distributed-lag non-linear models (lags 0–21 days) with quasi-Poisson regression, adjusting for seasonality, time trends, and day of week. City-specific estimates were pooled by random-effects meta-analysis, and attributable fractions were calculated using the forward perspective method. Both cold and heat were associated with increased mortality risk, following a U-shaped relationship. Minimum mortality temperature varied by 6.3°C across regions. Relative risks at the 10th and 90th percentiles were 1.95 (IQR 1.44–2.88) and 1.82 (IQR 1.39–2.81), respectively. Non-optimal temperatures accounted for 2.89% of deaths nationally (approximately 2,650 annually), with the highest fractions in the North (8.2%). Adults aged ≥65 years and Black individuals (for heat) showed the most significant vulnerability. Temperature extremes increase respiratory mortality across Brazil, with tropical regions exhibiting heightened vulnerability to cold despite warmer baseline climates. These findings support region-specific warning systems addressing both thermal extremes, with priority for older adults and Black populations.