The effects of a major natural disaster can linger and cause heart attacks and other health woes for years, according to a study released of New Orleans residents after Hurricane Katrina.

Four years after the massive hurricane swept through the celebrated southern US city in 2005, residents continued to experience a threefold increase in heart attacks, sustaining a trend witnessed two years after the event, it said.

“This data was surprising for us,” said Anand Irimpen, associate professor of medicine for the heart and vascular institute at Tulane University.

“We thought we would see a trend downward at four years,” said Prof. Irimpen, who presented the long-term study of post-disaster health consequences at the American College of Cardiology conference.

He describes the phenomenon as “Post-Katrina Stress Disorder,” whereby chronic stress exacerbates health problems and may give rise to psychological difficulties, which can also play a role in poor health.

The observational study was based on patients admitted to Tulane University Hospital with heart attacks in the two years prior to Katrina and the four years after hurricane. The hospital, which is inside the city itself, reopened five months after the storm.