Mortality risks associated with floods in 761 communities worldwide: time series study

Objective: To evaluate lag-response associations and effect modifications of exposure to floods with risks of all cause, cardiovascular, and respiratory mortality on a global scale. Design: Time series study. Setting: 761 communities in 35 countries or territories with at least one flood event during the study period. Participants: Multi-Country Multi-City Collaborative Research Network database, Australian Cause of Death Unit Record File, New Zealand Integrated Data Infrastructure, and the International Network for the Demographic Evaluation of Populations and their Health Network database. Main outcome measures: The main outcome was daily counts of deaths. An estimation for the lag-response association between flood and daily mortality risk was modelled, and the relative risks over the lag period were cumulated to calculate overall effects. Attributable fractions of mortality due to floods were further calculated. A quasi-Poisson model with a distributed lag non-linear function was used to examine how daily death risk was associated with flooded days in each community, and then the community specific associations were pooled using random effects multivariate meta-analyses. Flooded days were defined as days from the start date to the end date of flood events. Results: A total of 47.6 million all cause deaths, 11.1 million cardiovascular deaths, and 4.9 million respiratory deaths were analysed. Over the 761 communities, mortality risks increased and persisted for up to 60 days (50 days for cardiovascular mortality) after a flooded day. The cumulative relative risks for all cause, cardiovascular, and respiratory mortality were 1.021 (95% confidence interval 1.006 to 1.036), 1.026 (1.005 to 1.047), and 1.049 (1.008 to 1.092), respectively. The associations varied across countries or territories and regions. The flood-mortality associations appeared to be modified by climate type and were stronger in low income countries and in populations with a low human development index or high proportion of older people. In communities impacted by flood, up to 0.10% of all cause deaths, 0.18% of cardiovascular deaths, and 0.41% of respiratory deaths were attributed to floods. Conclusions: This study found that the risks of all cause, cardiovascular, and respiratory mortality increased for up to 60 days after exposure to flood and the associations could vary by local climate type, socioeconomic status, and older age.

What is already known on this topic: - Flood events are projected to increase in severity, duration, and frequency as a result of climate change. - Deaths from natural causes might increase after flood events, but current evidence is inconsistent. - Previous studies had limitations in exposure assessments, sample sizes, geographical areas, and study durations. What this study adds: -The findings of this study suggest that the risks of all cause, cardiovascular, and respiratory mortality reach a peak at around 25 days after exposure to floods and last for up to 60 days. - The associations appeared to vary with climate type and were stronger in populations with a low socioeconomic status or a high proportion of older people In communities impacted by floods, up to 0.10% of all cause deaths, 0.18% of cardiovascular deaths, and 0.41% of respiratory deaths were attributed to floods

Description

MCC Collaborative Research Network: Rosana Abrutzky, Micheline de Sousa Zanotti Stagliorio Coelho Coelho, Paulo Hilario Nascimento Saldiva, Nicolás Valdés Ortega, Patricia Matus Correa, Haidong Kan, Samuel Osorio, Aleš Urban, Francesco Sera, Mathilde Pascal, Alexandra Schneider, Veronika Huber, Ariana Zeka, Patrick Goodman, Francesca de'Donato, Paola Michelozzi, Masahiro Hashizume, Yoonhee Kim, César De la Cruz Valencia, Magali Hurtado Diaz, Ala Overcenco, Caroline Ameling, Danny Houthuijs, Gabriel Carrasco-Escobar, Xerxes Seposo, Baltazar Nunes, Iulian-Horia Holobaca, Ana Maria Vicedo-Cabrera, Aurelio Tobias, Jouni J K Jaakkola, Yasushi Honda, Fiorella Acquaotta, Noah Scovronick, Ho Kim, Whanhee Lee, Carmen Íñiguez, Martina S Ragettli, Shih-Chun Pan, Yue Leon Guo, Antonella Zanobetti, Joel Schwartz, Simon Hales.

Keywords

Floods Time Series Study Multi-Country Multi-City Climate Change Mortality Respiratory Tract Diseases Time Factors Determinantes da Saúde e da Doença Avaliação do Impacte em Saúde