- Experts analyze survey and health data on more than 3,000 older people in Japan
- They were 65 years of age and older in areas affected by tsunamis and earthquakes in 2011
- They found strong evidence for an increased risk of dementia in certain groups
- People from low-income backgrounds were at greatest risk of cognitive decline, the team discovered, especially the oldest, less educated and single.
As well as causing death and destruction, a study suggests that natural disasters can put people at greater risk of developing dementia.
Using health and survey data on people living in areas worst hit by the 2011 tsunami in Japan, Harvard University experts explored the link between cognitive decline and natural disasters.
The incident, which killed 20,000 people and saw 100,000 children being dismembered from their homes, may also have contributed to cognitive decline in older adults, they found.
More than 3,000 people with an average age of 73 were questioned about their cognitive status, with those who lost a home in the disaster experienced an increased rate of cognitive decline, but there was no effect of losing a loved one.
The team says it is linked to increased isolation, with the unmarried, the less educated and the eldest being at greatest risk of increasing cognitive decline.
Using health and survey data on people living in areas worst hit by the 2011 tsunami in Japan (pictured) gave experts at Harvard University in Cambridge, Massachusetts an insight into the link between cognitive decline and natural disasters .
The earthquake and tsunami caused havoc in Japan in 2011
The Thoku earthquake and tsunami affected Japan on March 11, 2011.
The earthquake measured 9.0–9.1 in magnitude and was an underwater megathrust earthquake with its epicenter in the Pacific Ocean.
It was about 45 miles east of the Oshika Peninsula in the Tohoku region of Japan and lasted six minutes.
It was so intense that it caused a tsunami in Japan, with waves reaching up to 133 feet in Miyako.
They traveled at 435 mph, reached six miles inland and gave local residents less than 10 minutes to evacuate the area.
Altogether there were 19,747 deaths, 6,242 injured and 2,556 missing.
Hundreds of thousands of people had been living away from their homes for years after the tsunami struck.
Recent studies suggest that there was also a link between the phenomenon, which destroyed homes and other buildings, and cognitive decline in some.
Longitudinal data were studied by Koichiro Shiba and colleagues, who wanted to know whether experiencing a tsunami directly and a magnitude 9 earthquake had an effect on cognition.
“Identifying a particularly vulnerable sub-population is important because it will contribute to allocating public health resources in future emergencies,” Shiba said. new scientist.
To understand the link, he turned to the Japan Gerontological Evaluation Study, which spoke to people aged 65 and older in the country at various points in time.
Shiba focused on data taken from Iwanuma in Miyagi Prefecture, as the area most affected by the tsunami.
Overall, they used information from 3,350 people with an average age of 73.2, with survey responses seven months before the disaster, and two and a half after the natural disaster, and then five years after follow-up.
They were asked about their cognitive status, which also included the responses of the caregivers, to obtain a comprehensive picture.
The team found that people who lost their homes during a natural disaster had an increased rate of cognitive decline.
‘Our analysis showed that the effects of home harm on subsequent cognitive dysfunction may be comparable with a diagnosis of stroke, which is a well-established risk factor of cognitive dysfunction,’ the authors wrote.
However, they were surprised to find that losing a loved one in a natural disaster did not make any difference to the rate of decline.
Sheeba said it was not clear why there was no correlation between losing someone close to a natural disaster and the rate of cognitive decline.
To get a better picture, the team used machine learning to compare individual specific situations, considering individual factors on the decline.
They found that people living on low incomes were most vulnerable to increased rates of cognitive decline when they went through a natural disaster.
This may be because they were more likely to be older, unmarried and less educated than those who did not suffer such a decline.
The incident, which saw homes destroyed (pictured), 20,000 killed and 100,000 children uprooted from their homes, may also have contributed to cognitive decline in older adults.
The team wrote, ‘Factors such as old age, unmarried status and living alone have intensified social isolation among exposed individuals.
Sheeba said she believes community centers should be built when a disaster strikes, to ‘encourage social interaction between residents’ to prevent social isolation.
Robbie Parks of Imperial College London, who was not involved in the study, told New Scientist that it is understandable that people in low-income areas suffer the most.
“This is an important study that sheds light on how the greatest burden of disasters such as earthquakes will fall on the most vulnerable, even in high-income countries such as Japan,” he explained.
More than 3,000 people with an average age of 73 were questioned about their cognitive status, with those who lost a home in the disaster experienced an increased rate of cognitive decline, but there was no effect of losing a loved one. stock image
Previous studies had looked at the effects of cognitive decline after a traumatic experience, but this is the first to take an individual look at the effect.
Studies have shown that some people are particularly prone to experience cognitive dysfunction after disasters, which can be overlooked in studies assessing only population mean associations, …