Researchers from the School of Public Health at the University of Texas Health Science Center (UTSPH) in Houston published a paper this week in Environmental Health that examined, for the first time, the impact of Houston’s 2011 heat wave on the health of the city’s population. The study aims were to determine if the heat wave had any effect on both the mortality rates, and number of emergency department (ED) visits in Houston, Texas.
Heat waves have important public health implications, especially in light of the current climate warming trends; for they have the potential to cause high rates of illness and death in vulnerable populations, such as the elderly. In the United States, an average of 400 deaths per year are directly related to heat, and an estimated 1,800 die from illnesses made worse by heat — including heat exhaustion, heat stroke, cardiovascular disease, and kidney disease. In times of record-breaking hot temperatures, it is important to be able to accurately assess the potential implications the extreme weather will have on the health of a population in a certain geographic area, for example Houston, Texas.
In August of 2011, Houstonians experienced a heat wave unlike any other on record. The heat wave occurred from August 2-30 according to the heat advisories issued by the National Weather Service. The 2011 summer was warmer than any previous summer since 1889; and the mean temperature of August was the highest among the temperature records of all previous months; and the all-time highest temperature 109.04 degrees Fahrenheit (42.8°C) occurred on August 27th.
In assessing the public health impact of the heat wave, lead study author Dr. Kai Zhang, PhD., Professor, Division of Epidemiology, Human Genetics and Environmental Sciences at UTSPH, and his team used the data from 20 Houston hospitals that accepted 911 ambulance deliveries from 2007 to 2011 to assess the number of ED visits. Original death records were obtained to determine daily mortality rates. Hourly weather data was assessed by utilizing information from the weather station located in the George Bush International Airport for the time period of 2007–2011.
The results showed that the heat wave did significantly increase the risk of ED visits among all age groups by 278 visits, with the largest effect on the elderly in which 66% of the visits were contributed by people between 60 and 65 years of age. Other important findings with public health importance include:
- 30 out 31 days in August in Houston had daily maximum temperatures above 100 degree Fahrenheit (37.8°C), and this led to the most consecutive days with issued heat advisories
- The average daily maximum, mean and minimum temperatures during the heat wave were 3.7, 2.5, and 1.4°C higher than their respective levels during the same days during 2007–2010.
- There was one more elderly death during the event compared to each of the previous years.
- Estimated heat-wave effects on mortality were not statistically significant.
When asked about the study findings, Dr. Charles Begley, PhD., Co-Director for the Center for Health Services Research, Director of the Houston Health Services Research Collaborative at UTSPH, and collaborating author, told BioNews that “Dr. Zhang has shown that heat waves in Houston have an impact on our health care system and lead to higher morbidity rates.”
This study adds to the growing body of literature that is focused on assessing the impact of temperature extremes that occur with heat waves on population health.