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.

Air Health Science Division Health Canada Ottawa ON Canada

Centre for Statistical Methodology London School of Hygiene and Tropical Medicine London UK

Centre on Climate Change and Planetary Health London School of Hygiene and Tropical Medicine London UK

Department of Geography University of Santiago de Compostela Santiago de Compostela Spain

Department of Public Health Environments and Society London School of Hygiene and Tropical Medicine London UK

EPIUnit Instituto de Saude Publica Universidade do Porto Porto Portugal

Faculty of Environmental Sciences Czech University of Life Sciences Prague Czech Republic

Institute of Atmospheric Physics Czech Academy of Sciences Prague Czech Republic

Laboratório para a Investigação Integrativa e Translacional em Saúde Populacional Porto Portugal

School of Epidemiology and Public Health Faculty of Medicine University of Ottawa Ottawa ON Canada

School of Public Health and Institute of Environment and Human Health Anhui Medical University Hefei China

School of Public Health and Preventive Medicine Monash University Melbourne VIC 3004 Australia

School of Public Health and Social Work Queensland University of Technology Brisbane QLD Australia

Shanghai Children's Medical Centre Shanghai Jiao Tong University Shanghai China

BMJ. 2023 Oct 4;383:2101. doi: 10.1136/bmj.p2101. PubMed

See more in PubMed

Hu P, Zhang Q, Shi P, Chen B, Fang J. Flood-induced mortality across the globe: Spatiotemporal pattern and influencing factors. Sci Total Environ 2018;643:171-82. 10.1016/j.scitotenv.2018.06.197. PubMed DOI

Rentschler J, Salhab M, Jafino BA. Flood exposure and poverty in 188 countries. Nat Commun 2022;13:3527. 10.1038/s41467-022-30727-4. PubMed DOI PMC

Tellman B, Sullivan JA, Kuhn C, et al. Satellite imaging reveals increased proportion of population exposed to floods. Nature 2021;596:80-6. 10.1038/s41586-021-03695-w. PubMed DOI

Yan M, Wilson A, Peel JL, et al. Community-wide Mortality Rates in Beijing, China, During the July 2012 Flood Compared with Unexposed Periods. Epidemiology 2020;31:319-26. 10.1097/EDE.0000000000001182. PubMed DOI PMC

Rocha LA, Fromknecht CQ, Redman SD, Brady JE, Hodge SE, Noe RS. Medicolegal Death Scene Investigations After Natural Disaster- and Weather-Related Events: A Review of the Literature. Acad Forensic Pathol 2017;7:221-39. 10.23907/2017.023. PubMed DOI PMC

Alderman K, Turner LR, Tong S. Floods and human health: a systematic review. Environ Int 2012;47:37-47. 10.1016/j.envint.2012.06.003. PubMed DOI

Dosa DM, Skarha J, Peterson LJ, et al. Association Between Exposure to Hurricane Irma and Mortality and Hospitalization in Florida Nursing Home Residents. JAMA Netw Open 2020;3:e2019460. 10.1001/jamanetworkopen.2020.19460. PubMed DOI PMC

Paterson DL, Wright H, Harris PNA. Health Risks of Flood Disasters. Clin Infect Dis 2018;67:1450-4. 10.1093/cid/ciy227. PubMed DOI

Obrová J, Sovová E, Ivanová K, Táborský M, Loyka S. Effects of the july 1997 floods in the Czech Republic on cardiac mortality. Disaster Med Public Health Prep 2014;8:492-6. 10.1017/dmp.2014.111. PubMed DOI

Milojevic A, Armstrong B, Hashizume M, et al. Health effects of flooding in rural Bangladesh. Epidemiology 2012;23:107-15. 10.1097/EDE.0b013e31823ac606. PubMed DOI

Bennet G, Controlled Survey of Effects on Health of Local Community Disaster . Bristol floods 1968. Controlled survey of effects on health of local community disaster. Br Med J 1970;3:454-8. 10.1136/bmj.3.5720.454. PubMed DOI PMC

Milojevic A, Armstrong B, Kovats S, et al. Long-term effects of flooding on mortality in England and Wales, 1994-2005: controlled interrupted time-series analysis. Environ Health 2011;10:11. 10.1186/1476-069X-10-11. PubMed DOI PMC

Gasparrini A, Guo Y, Hashizume M, et al. Mortality risk attributable to high and low ambient temperature: a multicountry observational study. Lancet 2015;386:369-75. 10.1016/S0140-6736(14)62114-0. PubMed DOI PMC

Zhao Q, Guo Y, Ye T, et al. Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modelling study. Lancet Planet Health 2021;5:e415-25. 10.1016/S2542-5196(21)00081-4. PubMed DOI

Milne BJ, Atkinson J, Blakely T, et al. Data Resource Profile: The New Zealand Integrated Data Infrastructure (IDI). Int J Epidemiol 2019;48:677-677e. 10.1093/ije/dyz014. PubMed DOI

Muñoz-Sabater J, Dutra E, Agustí-Panareda A, et al. ERA5-Land: a state-of-the-art global reanalysis dataset for land applications. Earth Syst Sci Data 2021;13:4349-83. 10.5194/essd-13-4349-2021. DOI

Brakenridge GR. Global Active Archive of Large Flood Events. Dartmouth Flood Observatory. https://floodobservatory.colorado.edu/ (accessed 18 Jul 2022).

Carozza DA, Boudreault M. A Global Flood Risk Modeling Framework Built With Climate Models and Machine Learning. J Adv Model Earth Syst 2021;13:e2020MS002221. 10.1029/2020MS002221 DOI

Kundzewicz ZW, Pińskwar I, Brakenridge GR. Large floods in Europe, 1985-2009. Hydrol Sci J 2013;58:1-7. 10.1080/02626667.2012.745082. DOI

Chen G, Guo Y, Yue X, et al. Mortality risk attributable to wildfire-related PM PubMed DOI

Scortichini M, Schneider Dos Santos R, De’ Donato F, et al. Excess mortality during the COVID-19 outbreak in Italy: a two-stage interrupted time-series analysis. Int J Epidemiol 2021;49:1909-17. 10.1093/ije/dyaa169. PubMed DOI PMC

Bhaskaran K, Gasparrini A, Hajat S, Smeeth L, Armstrong B. Time series regression studies in environmental epidemiology. Int J Epidemiol 2013;42:1187-95. 10.1093/ije/dyt092. PubMed DOI PMC

Sera F, Gasparrini A. Extended two-stage designs for environmental research. Environ Health 2022;21:41. 10.1186/s12940-022-00853-z. PubMed DOI PMC

Chen R, Yin P, Wang L, et al. Association between ambient temperature and mortality risk and burden: time series study in 272 main Chinese cities. BMJ 2018;363:k4306. 10.1136/bmj.k4306. PubMed DOI PMC

Parks RM, Benavides J, Anderson GB, et al. Association of Tropical Cyclones With County-Level Mortality in the US. JAMA 2022;327:946-55. 10.1001/jama.2022.1682. PubMed DOI PMC

Quist AJL, Fliss MD, Wade TJ, Delamater PL, Richardson DB, Engel LS. Hurricane flooding and acute gastrointestinal illness in North Carolina. Sci Total Environ 2022;809:151108. 10.1016/j.scitotenv.2021.151108. PubMed DOI PMC

Gasparrini A. Modeling exposure-lag-response associations with distributed lag non-linear models. Stat Med 2014;33:881-99. 10.1002/sim.5963. PubMed DOI PMC

Gasparrini A, Guo Y, Hashizume M, et al. Mortality risk attributable to high and low ambient temperature: a multicountry observational study. Lancet 2015;386:369-75. 10.1016/S0140-6736(14)62114-0. PubMed DOI PMC

Gasparrini A, Armstrong B, Kenward MG. Multivariate meta-analysis for non-linear and other multi-parameter associations. Stat Med 2012;31:3821-39. 10.1002/sim.5471. PubMed DOI PMC

Gasparrini A, Leone M. Attributable risk from distributed lag models. BMC Med Res Methodol 2014;14:55. 10.1186/1471-2288-14-55. PubMed DOI PMC

Borenstein M, Hedges LV, Higgins JPT, Rothstein HR. A basic introduction to fixed-effect and random-effects models for meta-analysis. Res Synth Methods 2010;1:97-111. 10.1002/jrsm.12. PubMed DOI

Button KS, Ioannidis JPA, Mokrysz C, et al. Power failure: why small sample size undermines the reliability of neuroscience. Nat Rev Neurosci 2013;14:365-76. 10.1038/nrn3475. PubMed DOI

Milojevic A, Armstrong B, Kovats S, et al. Long-term effects of flooding on mortality in England and Wales, 1994-2005: controlled interrupted time-series analysis. Environ Health 2011;10:11. 10.1186/1476-069X-10-11. PubMed DOI PMC

Lai H, Hales S, Woodward A, et al. Effects of heavy rainfall on waterborne disease hospitalizations among young children in wet and dry areas of New Zealand. Environ Int 2020;145:106136. 10.1016/j.envint.2020.106136. PubMed DOI

Quist AJL, Fliss MD, Wade TJ, Delamater PL, Richardson DB, Engel LS. Hurricane flooding and acute gastrointestinal illness in North Carolina. Sci Total Environ 2022;809:151108. 10.1016/j.scitotenv.2021.151108. PubMed DOI PMC

Schell CO, Reilly M, Rosling H, Peterson S, Ekström AM. Socioeconomic determinants of infant mortality: a worldwide study of 152 low-, middle-, and high-income countries. Scand J Public Health 2007;35:288-97. 10.1080/14034940600979171. PubMed DOI

Rainfall events and daily mortality across 645 global locations: two stage time series analysis