Burden of infant mortality associated with flood in 37 African countries

Abstract

Floods are becoming more frequent and severe in the context of climate change, with major impacts on human health. However, their effect on infant mortality remains unknown, particularly in low- and middle-income countries. We conducted a sibling-matched case-control study using individual-level data from Demographic and Health Surveys in Africa during 1990-2020. Individual flood experience was determined by matching the residential coordinates with flood events from the Dartmouth Flood Observatory database. Using data from 514,760 newborns, we found increased risks of infant mortality associated with flood exposure across multiple periods, with the risks remaining elevated for up to four years after the flood event. Overall, flood exposure was associated with 3.42 infant deaths per 1000 births in Africa from 2000 to 2020, approximately 1.7 times the burden associated with life-period exposure. This multi-country study in Africa provides novel evidence that flood events may increase infant mortality risk and burden, even over years after exposure.

Fig. 1. Distribution of flood events and study clusters in Africa, 1990–2020.

(A) The spatial distribution of flood events in Africa. (B) The spatial distribution of study clusters in Africa. The greyed area denotes no health data collected.

Fig. 2. Summary of the relationship between flood exposure and infant mortality in 37 African countries.

Changes and 95% confidence intervals in infant mortality (per 1000 births) associated with flood exposures at different months (A) or years (B), and classified by the severity of flood (C) and regions (D). Estimates in (C, D) were based on exposures at lag 0–4 year, which is the average of flood exposures at the concurrent year and preceding 4 years. Black solid circles indicate the point estimates of the effect, and the black vertical lines represent the 95% confidence intervals.

Fig. 3. The results of stratified analyses on the impacts of flood exposure on infant mortality.

Estimates were based on exposures at lag 0–4 year, which is the average of flood exposures at the concurrent year and preceding 4 years. Black solid circles indicate the point estimates of the effect, and the black vertical lines represent the 95% confidence intervals.

Fig. 4. Infant mortality burden associated with flood exposures in Africa (2000–2020).

The results were presented as excess deaths per 1000 liveborn births associated with 5-year average flood events, and illustrated in map (A, grids of 10 km × 10 km) and histograms (B, the country level). Estimates of flood-related infant mortality burden were based on exposures at lag 0–4 year, which is the average of flood exposures at the concurrent year and preceding 4 years.

Fig. 5. The temporal trend in estimated excess infant deaths (per 1000 liveborn birth) associated with flood exposure in Africa, 2000–2020.

Columns with error bars denote mean estimates with 95% confident intervals. The trend was illustrated with a polynomials spline with 3 degrees of freedom.