Dominic Royé1,2, Francesco Sera3, Aurelio Tobías4,5, Rachel Lowe6, Antonio Gasparrini3,7,8, Mathilde Pascal9, Francesca de'Donato10, Baltazar Nunes11, Joao Paulo Teixeira12. 1. From the Department of Geography, University of Santiago de Compostela, Santiago de Compostela, Spain. 2. CIBER of Epidemiology and Public Health (CIBERESP), Spain. 3. Department of Public Health Environments and Society, London School of Hygiene & Tropical Medicine, London, United Kingdom. 4. Institute of Environmental Assessment and Water Research (IDAEA), Spanish Council for Scientific Research (CSIC), Barcelona, Spain. 5. School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan. 6. Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, United Kingdom. 7. Centre for Statistical Methodology, London School of Hygiene & Tropical Medicine, London, United Kingdom. 8. Centre on Climate Change and Planetary Health, London School of Hygiene & Tropical Medicine, London, United Kingdom. 9. Santé Publique France, Department of Environmental Health, French National Public Health Agency, Saint Maurice, France. 10. Department of Epidemiology, Lazio Regional Health Service, Rome, Italy. 11. Department of Epidemiology, Instituto Nacional de Saúde Dr Ricardo Jorge, Lisbon, Portugal. 12. Department of Environmental Health, Instituto Nacional de Saúde Dr Ricardo Jorge, Lisbon, Portugal.
Abstract
BACKGROUND: There is strong evidence concerning the impact of heat stress on mortality, particularly from high temperatures. However, few studies to our knowledge emphasize the importance of hot nights, which may prevent necessary nocturnal rest. OBJECTIVES: In this study, we use hot-night duration and excess to predict daily cause-specific mortality in summer, using multiple cities across Southern Europe. METHODS: We fitted time series regression models to summer cause-specific mortality, including natural, respiratory, and cardiovascular causes, in 11 cities across four countries. We included a distributed lag nonlinear model with lags up to 7 days for hot night duration and excess adjusted by daily mean temperature. We summarized city-specific associations as overall-cumulative exposure-response curves at the country level using meta-analysis. RESULTS: We found positive but generally nonlinear associations between relative risk (RR) of cause-specific mortality and duration and excess of hot nights. RR of duration associated with nonaccidental mortality in Portugal was 1.29 (95% confidence interval [CI] = 1.07, 1.54); other associations were imprecise, but we also found positive city-specific estimates for Rome and Madrid. Risk of hot-night excess ranged from 1.12 (95% CI = 1.05, 1.20) for France to 1.37 (95% CI = 1.26, 1.48) for Portugal. Risk estimates for excess were consistently higher than for duration. CONCLUSIONS: This study provides new evidence that, over a wider range of locations, hot night indices are strongly associated with cause-specific deaths. Modeling the impact of thermal characteristics during summer nights on mortality could improve decisionmaking for preventive public health strategies.
BACKGROUND: There is strong evidence concerning the impact of heat stress on mortality, particularly from high temperatures. However, few studies to our knowledge emphasize the importance of hot nights, which may prevent necessary nocturnal rest. OBJECTIVES: In this study, we use hot-night duration and excess to predict daily cause-specific mortality in summer, using multiple cities across Southern Europe. METHODS: We fitted time series regression models to summer cause-specific mortality, including natural, respiratory, and cardiovascular causes, in 11 cities across four countries. We included a distributed lag nonlinear model with lags up to 7 days for hot night duration and excess adjusted by daily mean temperature. We summarized city-specific associations as overall-cumulative exposure-response curves at the country level using meta-analysis. RESULTS: We found positive but generally nonlinear associations between relative risk (RR) of cause-specific mortality and duration and excess of hot nights. RR of duration associated with nonaccidental mortality in Portugal was 1.29 (95% confidence interval [CI] = 1.07, 1.54); other associations were imprecise, but we also found positive city-specific estimates for Rome and Madrid. Risk of hot-night excess ranged from 1.12 (95% CI = 1.05, 1.20) for France to 1.37 (95% CI = 1.26, 1.48) for Portugal. Risk estimates for excess were consistently higher than for duration. CONCLUSIONS: This study provides new evidence that, over a wider range of locations, hot night indices are strongly associated with cause-specific deaths. Modeling the impact of thermal characteristics during summer nights on mortality could improve decisionmaking for preventive public health strategies.