In a retrospective study of health claims for 618 U.S. counties over 14 years, researchers found that severe drought conditions increased the risk of mortality among adults 65 or over.
“Even with all of this variability, we still observed an association between drought and health effects.” Michelle Bell, a professor at Yale F&ES and senior author of the study, noted, “These findings are critically important given that climate change is anticipated to increase the frequency and severity of droughts.” The study was conducted in collaboration with researchers at the Johns Hopkins Bloomberg School of Public Health and the Harvard T.H.
They identified periods of “non-drought” and “full drought,” and periods when droughts were “worsening.” In periods when droughts were worsening, they further broke down the drought days into “low severity” and “high severity.” They then used Medicare claims made between Jan. 1, 2000 and Dec. 31, 2013, to calculate daily rates of cardiovascular admissions, respiratory admissions, and deaths among individuals 65 and over.
But when drought escalated to periods of “high severity worsening” conditions, the researchers found, mortality risk increased by 1.55%.
However, one possibility is that drought changes growing seasons or impacts the allergens that influence respiratory illnesses, said the researchers, noting that dry conditions also trigger more dust and particulate matter in the air.
While further research can examine these different factors, Berman said, the new findings provide an important basis.
“Because this was an initial study, we wanted to capture as wide a picture as we could and not isolate ourselves to a tiny snapshot,” he said.
The good news, Berman said, is that droughts, unlike other extreme weather events, are slow-moving.
“Once we’re able to identify the mechanisms behind these effects, we can intervene before drought reaches that severe stage.
Other researchers included Keita Ebisu, a postdoctoral associate at F&ES, and Roger Peng, a professor of biostatistics at the Johns Hopkins Bloomberg School of Public Health.