Emergency respiratory hospitalisations among the elderly is increased by outdoor heat

by Bruce Sylvester – Increases in outdoor heat significantly raise, for the elderly, the risk of emergency hospitalisation for respiratory disorders, researchers reported online on March 8, 2013 ahead of print publication in the American Journal of Respiratory and Critical Care Medicine.

The epidemiological study included data on over 12.5 million Medicare (USA) beneficiaries.

“While outdoor heat has been shown to increase respiratory mortality, evidence on the relationship between heat and respiratory hospitalisations has been less consistent,” said lead author G. Brooke Anderson, PhD, postdoctoral fellow in the Department of Biostatistics at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland. “In the largest population of the elderly yet studied, we found strong evidence that short-term exposure to outdoor heat increases the risk of hospitalisation for COPD and respiratory tract infections. This relationship was consistent for men and women and across all age groups studied.”

The investigators gathered and evaluated data from 213 urban counties in the United States; over 30 percent of the U.S. population aged 65 and older were included in the study. They also gathered data on Medicare emergency respiratory hospitalisations from 1999-2008, plus measures of weather conditions and air pollution.

They found that, on average, respiratory hospitalisations increased 4.3 percent for each 10°F increase in daily mean summer temperature. This correlation did not change with adjustments for air pollution, age, gender or seasonal trends in hospitalisation rates and temperature.

The correlation was strongest on the day of heat exposure and remained elevated the day following exposure.

Each 10°F increase in daily temperature translated to approximately 30 excess respiratory hospitalisations per day among the elderly in the 213 counties.

The increased risk for heat-related hospitalisation was 4.7 % for COPD and 4.1% for respiratory tract infections.

“Our study provides clear and consistent evidence of a link between outdoor heat and hospitalisation for respiratory disease in the elderly,” said senior author Roger D. Peng, Ph.D, associate professor in the Department of Biostatistics at the Johns Hopkins Bloomberg School of Public Health. “As the prevalence of respiratory conditions and the age of the population continue to increase and global temperatures continue to rise as a result of climate change, the risk of heat-related respiratory disease is also likely to increase.”