Drought can slightly increase developing world children’s risk of diarrheal disease, researchers have found, adding that wetter regions seem to be affected differently than drier ones.
Diarrhea is the second-leading cause of death among children worldwide, and climate change is making droughts longer, more frequent and more severe, the new study published in the journal Nature Communications found.
The study, based on data from 51 low- and middle-income countries, found that children were more likely to recently have had diarrhea following six months to two years of drought conditions, although the effect of drought differed across dry, temperate and tropical climate zones.
Previous studies found links between diarrheal disease and rainfall, flooding and seasonality, but little was known before about the effects of drought.
The new study “fills that void of understanding the impacts associated with drought specifically, as opposed to flooding, extreme rains and seasonality,” said epidemiologist Joseph Eisenberg of the University of Michigan, who was not involved in the study.
“Water plays an essential role both in helping address the problem as well as increasing the risk of being exposed,” he said.
Water essential for good hygiene
Water is central to the spread and prevention of diarrheal disease. Germs that cause diarrhea survive and spread in water, but water is also important for hygienic practices, such as hand-washing, that prevent infections.
Study author Pin Wang, an environmental epidemiologist at Yale University, and his colleagues thought drought could force families to prioritize scarce water for drinking rather than washing, leaving children more vulnerable to diarrhea.
“Drought can directly impact the WASH (Water, Sanitation, and Hygiene) practices,” Wang said. “Because of the insufficient water supply, people might prioritize the water for other necessary uses, such as drinking, but not for washing hands and also flushing [the] toilet.”
Wang and his colleagues combined weather records with data on diarrhea in over 1.3 million children under the age of 5 from the Demographic and Health Surveys Program, which surveys representative families to collect data on health and demographics in the developing world. The Demographic and Health Surveys data also included information on each child, household wealth and WASH practices.
Using this data, the researchers then determined whether the children in the dataset had experienced drought, how long the drought had lasted, and how severe it had been relative to normal conditions.
Correcting for differences among households and individual children, the researchers found that exposure to a six-month drought slightly increased the risk of diarrhea in children under age 5. Risk was 5% higher after mild drought and 8% higher after severe drought, though the strength of drought’s effect on diarrhea depended on other factors, such as local climate, hygiene and water access.
In dry regions, droughts lasting six months did not affect diarrhea rates significantly, but droughts lasting two years did.
The authors speculate that it may be because these dry regions are already prepared for short periods of water scarcity but can’t cope with very long droughts. On the other hand, tropical and temperate regions saw worse effects in six-month droughts than in longer ones, perhaps because they are less prepared for water shortages in the short term but have more water available in general to help adapt in the long term.
The researchers found that families in a drought washed their hands and performed other WASH practices less often than those who were not experiencing drought. That accounted for about 10% of the increase in diarrhea rates in mild drought and about 20% in severe conditions.
Children whose families need to walk more than 30 minutes to collect water also had a higher risk of diarrhea associated with severe drought than those whose families had water nearby.
More studies needed
Eisenberg said that the study was a good first step, but that more studies would be needed to confirm the results.
“I think the biggest implication … as a hypothesis-generating result is that it will promote and motivate people to conduct some more sophisticated studies to sort of back up the findings,” he said.
Wang also said that future studies would be needed to back up his findings. And as climate change is expected to shake up rainfall patterns around the world, he said he hopes his result will translate into policy that would protect children from diarrheal disease brought on by drought.
“We obviously think that with climate change, there will be higher incidence of drought events in the future, particularly … in the places where it's already having less rainfall right now,” Wang said. “We need to reduce the greenhouse gas emissions, that's the first thing. The second is that the WASH variables should be emphasized or prioritized — particularly in these low- and middle-income countries. People need better WASH practices to reduce their diarrhea risks.”