Researchers examined death statistics and hospital admissions for cardiovascular and respiratory disease during non-drought, worsening, and improving drought conditions in western states over a 14-year period, from 2000 though 2013.
The retrospective analysis, which also showed a statistically-significant reduction in hospitalizations for respiratory illness during full drought periods, is among the first studies to examine the impact of drought on health in the U.S., Jesse D. Berman, PhD, of Yale University in New Haven, Conn., and colleagues, wrote in Lancet Planetary Health, a new journal launching this month.
These data were compared with hospital admissions among people age 65 and older identified through Medicare claims made during the period in an effort to calculate daily rates of cardiovascular admissions, respiratory admissions, and death.
The analysis revealed that: Respiratory hospital admissions significantly decreased by -1.99% (95% posterior interval, -3.56% to -0.38%) during periods of full drought compared to no drought, but not during worsening drought conditions Risk for death increased by a statistically significant 1.55% (0.17%-2.95%) during high-severity worsening drought conditions compared to no drought, but not during full drought or low-severity worsening drought conditions Drought status was not significantly associated with cardiovascular admissions In areas where droughts occurred less frequently, however, both mortality and cardiovascular hospitalizations showed statistically significant increases during drought.
Specifically, in counties with less than 20% of days classified as drought periods (314 counties), high-severity worsening drought was associated with a 4.4% increase in mortality and a 9.3% increase in cardiovascular hospital admission, compared with non-drought periods.
"Although as drought becomes more common, we might observe population acclimatization making future health effects less pronounced, an outcome seen in studies of temperature and heat waves."
Although not significant, the researchers found that the risk of death was four times greater in rural counties than urban counties during high-severity, worsening drought.
Another potential study limitation included possible misclassification of both exposure and disease.
"One area that remains to be investigated is what measures or characteristics of drought are most predictive of health effects?"
Balbus wrote.