Parks’s team estimated that, among Medicare patients alone, tropical cyclones are associated with nearly seventeen thousand excess hospitalizations per decade in the United States. “It’s shocking, to be honest,” Parks told me. He sees each hurricane as a profound disruption to affected communities. “Once the water subsides, it becomes a huge, invisible burden,” he said. The hazards extend beyond rain, flooding, or wind. “They’re existential,” he said. “They pull at every element of the fabric of society.”
A decade ago, two researchers, Edward Rappaport and B. Wayne Blanchard, set out to measure what they called the indirect deaths from storms: “Casualties that, while not directly attributable to one of the physical forces of a tropical cyclone, would not be expected in the absence of the storm.” How many more people are harmed than the official tallies suggest? “To answer those questions, one is faced with others,” the researchers wrote in a 2016 paper. How far in advance of a storm should they search? (During evacuations, a person could die from an untreated emergency or a car crash.) How long after? (Injuries can cause death weeks after they occur.) How far from the storm’s center? Where, and when, and in what way, should they look?
Rappaport and Blanchard settled on an old-fashioned methodology: scouring reams of death records in the vicinity of fifty-nine storms, dating back to 1963. (To look back at Hurricane Camille, in 1969, they reviewed more than a thousand death-certificate records.) The pair ultimately identified more than fourteen hundred indirect deaths—almost as many as the total number of direct deaths reported from the storms. Many fatalities, such as electrocutions from downed power lines, were accidental. But the largest share reflected Irimpen’s findings from New Orleans. “Heart attacks and other cardiovascular failures are the most pervasive elements in indirect deaths,” the researchers wrote. Most seemed to be triggered by physical exertion—loading sandbags before Hurricane Wilma, for example, or bailing water out of a car owing to Hurricane Floyd. But, during Hurricane Hugo, in 1989, one man reportedly dropped dead after he “saw everything he had, totally demolished.” Their research echoed findings from other studies of disasters. Three years after a 2004 earthquake in Japan, mortality from heart attacks was found to be fourteen per cent higher than pre-quake. In the two weeks after Hurricane Sandy, New Jersey recorded thirty-six more strokes and a hundred and twenty-five more heart attacks than usual. Many were fatal.
Elena Naumova, a data scientist at Tufts, was part of a team that analyzed around four hundred thousand Medicare hospitalizations after Katrina. They found that hospitalizations for cardiovascular problems increased up to sixfold, and remained elevated for two months. “These are hidden consequences,” Naumova told me. “It’s very hard to connect what happens months later to the hurricane . . . but the risks linger for a long time.” Naumova now thinks of a storm as similar to an outbreak whose effects ripple out in her data. “The health-care system will be constantly bombarded by these cascading effects,” she said. “You see one wave, and another, and another.”
When researchers want to study the collateral consequences of a major event, whether a natural disaster or a pandemic, they often use the concept of excess deaths. Mortality rates don’t capture the full extent of harm; for one thing, they exclude injuries and illnesses that people recover from. But they can capture broad trends that might otherwise escape notice. When Hurricane Maria devastated Puerto Rico, in 2017, the official death toll was sixty-four—a number that seemed low, given the storm’s violence. Then a team of researchers surveyed more than three thousand households, searching for fatalities that could be related to Maria. Based on their results, they estimated that mortality had likely increased more than sixty per cent in the three months after the storm. If all of Puerto Rico experienced a similar uptick, the storm would be responsible for nearly five thousand excess deaths.
Rachel Young, an environmental economist at the University of California, Berkeley, told me that she had read the Hurricane Maria paper and had an idea: perhaps she’d find a signal if she studied mortality across the entire United States. Young and Solomon Hsiang, a colleague at Stanford, tried to link state-by-state mortality data to five hundred tropical cyclones since 1930. “I ran the analysis, and I thought I must be doing something wrong,” she told me. “We were stunned.” Their results, published last year in Nature, suggested that the average tropical cyclone generated between seven and eleven thousand excess deaths, up to fifteen years after the storm—three hundred times as many as NOAA had tallied. For years, they tried repeatedly to invalidate their findings. “We really wanted to stress-test the result,” Young told me. In the end, they concluded that large storms “reverberate for so much longer than we thought,” she said. “They’re not just disasters of the week.”
One of the most striking findings in Young and Hsiang’s paper hinted at how storms were causing long-term damage. Infants were impacted more than any other group—and many died at least twenty-one months after the storm in question, meaning that they had not been conceived at the time of landfall. This suggested that “cascades of indirect effects,” not “personal direct exposure,” were proving deadly, Young and Hsiang wrote. Displaced people may lose access to medical care, child care, and support networks; disasters undermine not only physical but also mental health.
Irimpen’s research at Tulane helps pick apart these cascades. In his initial study, two years post-Katrina, he observed increased unemployment, lack of insurance, smoking, and substance abuse—but not an increase in risk factors traditionally associated with cardiovascular disease, such as diabetes or high blood pressure. Ten years later, however, these illnesses had increased as well. “We think there is a compounding effect,” he explained. Stress and adverse behaviors contribute to chronic diseases, which then further increase the risk of heart attacks. The disaster’s impacts were lasting enough that some of these trends took a decade to detect.