Health conditions related to heat are sharply rising and may affect ethnic populations disproportionately, California statistics suggest.
The data were compiled by the California Environmental Health Tracking Program, which tracks emergency room visits and hospitalizations due to heat-related medical conditions such as exhaustion and heat stroke.
Over the course of a decade, emergency room visits for heat-related illness increased across California by 35 percent, researchers found.
The increase was higher in minority groups such as African-Americans and Hispanics than in the population overall.
Between 2005 and 2015, heat-related emergency department visits rose by an average of 67 percent for African-Americans, 53 percent for Asian Americans and 63 percent for Hispanics. These visits increased by only 27 percent among whites.
The rates for African-Americans and Asians were always higher than for the overall population across the decade. Hispanic populations and white populations had similar increases in rates until 2013, after which the rates diverged.
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The research was conducted at the Weill Cornell Medicine campus in Doha, Qatar. Investigators there started studying the data to compare California with Doha, which also sees a high amount of heat-related illness, and with other places.
"California just happened to have very good, publicly available data," said study co-author Dr. Grigory Ostrovskiy.
Older research has showcased the vulnerability to heat-related-illness among ethnic minorities in agricultural occupations. But Ostrovskiy and his colleague Ziyad Mahfoud, along with medical student Rana Abualsaud, wanted to know whether this gap was worsening or improving over time, they explain in Wilderness & Environmental Medicine.
More research is needed to identify the cause of the disproportionate rate increases, the researchers say. The study is also limited because the data across the years may not be uniform and may not account for migration to and from hotter counties in the state, the team notes.
However, they add, minorities are likely to be of lower socioeconomic status and to live in densely populated areas with no air conditioning.
"As global temperatures are rising, summers are getting hotter," Ostrovskiy told Reuters Health by email. "When this happens, people who cannot change their environment, or are otherwise vulnerable, end up being exposed to more heat than their body can get rid of."
"All ethnicities are coming to the hospitals more often with heat related illness, but minorities are even more disproportionately affected than they were before," he said.
Dr. Marc Schenker, a distinguished professor of public health sciences and medicine at University of California, Davis, who was not involved in the study, told Reuters Health he thinks the study "was very appropriately cautious in conclusions, mentioning a lot of possibilities for the observation."
"It highlights a few issues - one is climate change. As you know, four of the five hottest years in record were in the past five years. Climate change is real and it's something that has kind of crept up on us," he said.
However, he cautioned, climate change is likely not the only reason for an increase in heat-related illness.
"I wouldn't be surprised if there were other factors in terms of health services that were involved, such as lack of care or delayed care," Schenker said.