People with dementia had a significantly higher risk of contracting the coronavirus and were much more likely to be hospitalized and die of it than people without dementia, a new study of millions of medical records in the United States found.
The risk cannot be fully explained by characteristics common to people with dementia that are known risk factors for Covid-19: old age, living in a nursing home and having conditions such as obesity, asthma, diabetes and cardiovascular diseases. After the researchers adjusted these factors, Americans with dementia were still twice as likely to get Covid-19 last summer.
“It is very convincing to suggest that there is something about dementia that makes you more vulnerable,” said Dr. Kristine Yaffe, a professor of neurology and psychiatry at the University of California, San Francisco, who was not involved in the study.
The study found that blacks with dementia were almost three times more likely to be infected with the virus than whites with dementia, a finding that experts say probably reflects the fact that people of color were generally disproportionately harmed during the pandemic.
“This study highlights the need to protect patients with dementia, especially those who are black,” wrote the authors.
Maria Carrillo, scientific director of the Alzheimer’s Association, which runs the newspaper that published the study, Alzheimer’s and Dementia, said in an interview: “One of the things that resulted from this situation at Covid is that we should point out these disparities. “
The study was conducted by researchers at Case Western Reserve University, which analyzed electronic health records of 61.9 million people aged 18 and over in the United States from February 1 to August 21, 2020. The data, collected by IBM Watson Health Explorys, arrived from 360 hospitals and 317,000 health care providers in all 50 states and represented a fifth of the American population, the authors said.
Rong Xu, a professor of biomedical informatics at Case Western and senior author of the study, said there was speculation about whether people with dementia were more prone to infections and damage from Covid-19.
“We thought, ‘We have the data, we can just test that hypothesis,'” said Xu.
The researchers found that of 15,770 patients with Covid-19 in the medical records analyzed, 810 of them also had dementia. When the researchers adjusted for general demographic factors – age, sex and race – they found that people with dementia had more than three times the risk of contracting Covid-19. When they adjusted Covid’s specific risk factors, such as nursing home residence and underlying physical conditions, the gap narrowed slightly, but people with dementia were still twice as likely to be infected.
Experts and the study’s authors said the reasons for this vulnerability could include cognitive and physiological factors.
“People with dementia depend more on people around them to do things safely, to remember to wear a mask, to keep people away from social distance,” said Dr. Kenneth Langa, professor of medicine at the University of Michigan, who was not involved in the study. “There is cognitive impairment and the fact that they are more at social risk,” he said.
Dr. Yaffe said there may also be an “element of fragility” for people with dementia, including lack of mobility and muscle tone, which can affect their resilience to infections.
Dr. Carrillo noted that coronavirus infection was associated with an inflammatory response that has been shown to affect blood vessels and other aspects of the circulatory system. Many people with dementia already have vascular impairment, which can be aggravated or amplified by Covid-19.
In fact, the study’s authors subdivided patients by the type of dementia listed in the electronic records and found that people designated as having vascular dementia had a higher risk of infection than people designated as having Alzheimer’s disease or other types.
But Dr. Langa and Dr. Yaffe warned that there was a significant overlap between types of dementia. Many patients have Alzheimer’s and vascular pathology, they said, and doctors who are not specialists may not be able to distinguish subtypes when providing codes for electronic records.
In examining the risk of hospitalization and death for Covid patients with dementia, the researchers made no adjustments to demographic data such as age or whether they lived in nursing homes or had underlying medical conditions. They found that Covid patients with dementia were 2.6 times more likely to have been hospitalized during the first six months of the pandemic than those without dementia. They were 4.4 times more likely to die.
Black people with Covid-19 and dementia were significantly more likely to be hospitalized than white people who had both diseases. The authors did not find a significant difference in the mortality rate of patients with black and white coronavirus with dementia, although they wrote that the number of deaths analyzed, 170, may be too small to provide a solid conclusion on this.
The experts noted that a limitation of the study was that the researchers did not have access to socioeconomic information, which could provide a greater understanding of patients’ risk factors.
Dr. Langa also noted that the data reflected only the people who interacted with the health system, so it does not include “more isolated and poorer patients who have more difficulty reaching doctors”.
Consequently, he said, the study may be “an underestimation of the greatest risk of Covid infection for people with dementia”.