NEW YORK (Reuters Health) - Heart attacks are usually most common on weekdays and mornings, especially Mondays, but new data analysis shows that pattern reversed in New Orleans after Hurricane Katrina.
"The fact that it's such a polar opposite shift is really surprising," lead author Dr. Matthew Peters of Tulane University told Reuters Health.
After the storm the overall number of attacks tripled, likely due to an increased number of smokers. They were more likely on weekday evenings and weekends, according to data published in The American Journal of Cardiology.
Before the hurricane, 23 percent of heart attacks happened on Mondays, in line with national averages. After, 10 percent happened on Mondays, less than any other day of the week.
Previous research has attributed the usual excess of Monday and morning heart attacks to work stress, which also peaks on Mondays and in the morning. Researchers were puzzled to find the pattern reversed after the hurricane.
"Studies before have looked at the overall increase in (heart attack) after disasters, like the earthquake in Japan and Katrina, but this is the first time we've looked at the timing," Peters said.
If the result holds up after further study, the study authors offer a tentative explanation: sources of stress change in a city following a major disaster.
Peters suggests that for people put out of work by the storm, Mondays stopped being particularly draining. "People aren't getting up and going to work, and home lives are even more difficult," said Peters. For those still working, a job became a welcome break from stresses of hurricane related fallout at home.
That "stress relief at work" reasoning doesn't account for all the findings, David Krantz, who studies stress induced heart attacks at Uniformed Services University of the Health Sciences in Bethesda, Maryland, told Reuters Health in an email.
Morning heart attacks have been attributed to hormone shifts and increased strain on the heart while waking up, which wouldn't be affected by a hurricane, said Krantz.
Data were limited to one medical center, Tulane University Hospital. A previous study based on data from the same hospital found that after the storm, more heart attack patients lacked insurance, had temporary housing, were divorced and failed to regularly take prescribed medications (see Reuters story of April 3, 2011: reut.rs/hXnOhQ).
"It doesn't confirm yet that experiencing the storm changed people, the storm may simply have changed who remained in town," Kathryn Roecklein, who studies the influence of body rhythms on biology at the University of Pittsburgh, told Reuters Health.
Katrina displaced 1.3 million Gulf Coast households who were dispersed through all 50 states, temporarily or permanently. "A disaster that didn't cause people to move away from the area might make for a better test of this question," said Roecklein.
The study also did not take into account other factors that changed between the groups. Post-Katrina patients were on average younger, more unemployed, less likely to be insured and more likely to smoke, which is a sizeable risk factor for heart attack. These changes might have influenced the shift in heart attack timing, but at this point Krantz says it's difficult to tell.
There are likely mental and physical health consequences of natural disasters yet to be discovered, said Krantz.
"The usual pattern was obliterated, and this may affect more conditions than heart attack," said Peters.
SOURCE: bit.ly/118Sc10 The American Journal of Cardiology, January 7, 2013.