Kales and his colleagues examined 103 firefighter fatalities described by the National Institute for Occupational Safety and Health. They looked at circadian and job activity data, adjusting for the estimated average time per year spend in each activity.
"Strenuous physical activity preceding the event was more likely to be reported for CHD deaths than for trauma deaths," Kales revealed. "Compared to non-emergency duty, the risk of CHD death was increased during fire suppression, training and alarm response."
And, he noted, 77 percent of firefighter CHD fatalities occurred between noon and midnight, unlike CHD deaths in the general public, which peak between 6 a.m. and noon. "This likely reflects peak hours for emergency calls," said Kales. "Our findings suggest that on-duty CHD fatalities are often precipitated by specific occupational activities."