New York: Japan's 2011 Fukushima earthquake, the most powerful ever recorded in that country, generated a killer tsunami, a nuclear power plant disaster and aftershocks of another sort - a 70 percent rise in cardiac arrests, particularly among people age 75 and older, according to a new study.
Those heart-related repercussions echoed through the population for more than a month, researchers report in the New England Journal of Medicine.
The magnitude 9.0 quake struck on March 11. Dr. Tetsuhisa Kitamura of Osaka University and his colleagues focused on the three hardest-hit prefectures of Iwate, Miyagi and Fukushima, where 15,814 people died, 2,664 were left missing and 448,922 ended up as refugees.
Kitamura and coauthor Dr. Taku Iwami of Kyoto University Health Service said in a joint email that, based on past experience, the increase was not surprising.
"Earthquake was well-known to be one of the risk factors for sudden cardiac arrest and acute coronary syndrome (heart attack)," they said. "However, little is known about the impact of earthquake on these diseases by age and sex, and in this study, showing the differences provides new insights on disaster medicine."
Using an ambulance-based registry, they looked at weekly counts of cardiac arrest cases that occurred outside a hospital from four weeks before and eight weeks after the date March 11 in the years 2005 to 2011.
Cardiac arrest is when the heart stops beating entirely, often due to an electrical problem that causes abnormal rhythms - which in turn can be brought on by anxiety or stress or by defects in the heart. Once it stops, unless the heart is restarted within minutes, cardiac arrest is usually fatal.
Normally, roughly 75 cardiac arrests would have been expected each week during the period researchers examined. But the week after the quake itself, the number of cases jumped 70 percent compared to that week in the previous years. The number was 48 percent higher the following week.
The risk kept declining gradually - it was 47 percent higher than in pre-quake years the third week, 26 percent higher the fourth week and 25 percent higher the fifth week. In the sixth week after the disaster, the rate was close to the same as that of previous years, despite two strong aftershocks above 7.0 magnitude on April 7 and April 11.
The researchers found that not all groups were affected equally. Residents age 75 and older faced a much greater risk than younger residents, probably because of age-related risk factors, they said.
Among older men, the rate of cardiac arrests increased by as much as 53 percent during the first two weeks after the initial quake and 68 percent one week after the two aftershocks. Even in the eighth week following the quake, their rate was 51 percent higher than anticipated.
Older women showed an even greater jump in risk, by 92 percent the week of the quake and 72 percent two weeks later, followed by a gradual decline.
"The risk of out-of-hospital cardiac arrest did not increase significantly among men between the ages of 18 and 74 years," Kitamura's team wrote in its paper, "but it did increase significantly among women in the same age group during the first two weeks after the earthquake."
Among those younger women, whose heart risks are generally low, the rate of cardiac arrests spiked nearly four-fold during the first week after the quake and three-fold during the second week, before dropping to normal.
"A previous report showed that acute earthquake-induced stress increased the occurrence of…(stress-induced cardiomyopathy without structural heart change) as a cause of sudden cardiac arrest, especially in women," the researchers speculated in their email. "Younger men might have tolerance for the stress by the earthquake, we guess."
Dr. Anand Irimpen of the Heart & Vascular Institute of the Tulane University School of Medicine in New Orleans, who was not involved in the new study but has examined heart attack rates after Hurricane Katrina devastated New Orleans in 2005, said the effects of such disaster can linger.
He and his colleagues found a three-fold increase in heart attacks two years after that Category 5 storm.
Irimpen said in a telephone interview, "It's coming back and the stress of rebuilding" that seems to be playing a key role in the higher rate.
"But I feel lack of medication could also be a contributing factor in people at high risk for heart attack, such as diabetics and people with high blood pressure," said Irimpen who is also chief of cardiology at Southeast Louisiana Veterans Health Care System.
"Sometimes just basic pharmaceuticals are not available for people returning to the area, he said. "So what we recommend for a disaster, where you have some warning, is to have backup medications for a month or two, or have a prescription on hand so when you leave town you can get your medication refilled."
Drs. Kitamura and Iwami said in their email that they are not sure what effect the nuclear meltdown might have had on the higher rates of cardiac arrest, if any. "The news might be a stress and affect the occurrence of sudden cardiac arrest, but in this study we did not aim to evaluate the impact of the nuclear accident."