A team from Rice University and the Houston Fire Department EMS has found a direct correlation between out-of-hospital cardiac arrests (OHCA) and levels of air pollution and ozone. The research, based on a massive data set unique to Houston, was published this month in the American Heart Association journal Circulation.More at linkThe authors analyzed eight years’ worth of data drawn from Houston’s extensive network of air-quality monitors and more than 11,000 concurrent OHCA logged by Houston Emergency Medical Services (EMS). They found a positive correlation between OHCAs and exposure to both fine particulate matter (airborne particles smaller than 2.5 micrograms) and ozone.
The researchers found that a daily average increase in particulate matter of 6 micrograms per day over two days raised the risk of OHCA by 4.6%, with particular impact on those with pre-existing (and not necessarily cardiac-related) health conditions. Increases in ozone level were similar, but on a shorter timescale: Each increase of 20 parts per billion over one to three hours also increased OHCA risk, with a peak of 4.4%. Peak-time risks from both pollutants rose as high as 4.6%. Relative risks were higher for men, African-Americans and people over 65.
For the study, OHCA events were defined as cases where EMS personnel performed chest compressions. The patients died in more than 90% of the cases, which occurred more during the hot summer months (55% of total cases).
The researchers also looked at the effects of nitrogen dioxide, sulfur dioxide and carbon monoxide levels, none of which were found to impact the occurrence of OHCA.
Katherine B. Ensor; Loren H. Raun; David Persse (2013) A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution. Circulation. doi: 10.1161/CIRCULATIONAHA.113.000027
This is an interesting and important finding.