(RxWiki News) Several diseases may factor into an older, gravely ill person’s death. Alzheimer’s may be one of those diseases, but it might not be listed as the primary cause of death.
A new study has suggested that rates of death from Alzheimer’s disease in the United States may trail closely behind the number of deaths from heart disease (leading cause of death) and cancer (second leading cause).
Right now, the US Centers for Disease Control and Prevention (CDC) ranks Alzheimer’s as the sixth leading cause of death, based on information from US death certificates.
"Raise your awareness of Alzheimer's disease and treatment."
Bryan James, PhD, a researcher in the Alzheimer’s Disease Center at Rush University Medical Center in Chicago, was lead author of this six-person research team.
The study ran from September 1997 through February 2013. Its participants consisted of 2,566 people, aged 65 and older, who did not have dementia when the research began and who were enrolled in either the Rush Memory and Aging Project or the Religious Order Studies. The religious studies involve priests, nuns and other clergy being treated at various medical facilities across the country. The Rush Memory and Aging Project includes residents of retirement communities and other housing for seniors in Illinois.
The participants in the current study were followed for an average of eight years.
Group members were tested yearly for dementia, a loss of memory and other functions needed for daily living that usually worsen over time. Alzheimer’s is the most common form of dementia.
Of the 2,566 study participants, 559 (21.8 percent) were diagnosed as not having dementia at the start of the study but were diagnosed with Alzheimer's during the study period. In addition, 31 others (1.2 percent) were diagnosed with a form of dementia other than Alzheimer's.
Of the study participants who died, 72 percent had developed Alzheimer's. Among those who did not develop Alzheimer's, 34.5 percent died.
Of all 2,556 people, 1,090 persons (42.4 percent) died during those eight years.
After the patients died, brain autopsies confirmed that about 90 percent of those who had been diagnosed with dementia had Alzheimer’s. While Alzheimer’s is diagnosed using a series of tests and by ruling out other diseases, Alzheimer’s cannot be fully confirmed until after a person dies and abnormal deposits of protein are found on the brain.
In this study, those whose deaths were attributed to dementia died an average of four years after their dementia diagnosis.
People aged 75 to 84 who were diagnosed with dementia died at four times the rate of others in that age group who did not have Alzheimer's. People who were at least 85 years old died at three times the rate of others in that age range who did not have Alzheimer's.
Based on their findings, Dr. James and colleagues concluded that Alzheimer’s was the leading cause of death in more than a third of deaths of patients aged 75 and older. That meant that, in 2010, about 503,400 deaths of people aged 75 and older were from Alzheimer’s. That rate is roughly five to six times higher than the 83,494 deaths in 2010 that the CDC linked to Alzheimer’s. Those CDC numbers were based on what death certificates listed as the official cause of death.
Dr. James and team wrote that their numbers are a rough estimate of Alzheimer's cases. Their "figure suggests that [Alzheimer's disease] may be the third leading cause of death after heart disease ad cancer, with nearly as many deaths as chronic lower respiratory diseases, strokes, and accidents ... combined," these researchers wrote.
Respiratory disease ranks third, stroke ranks fourth and accidents rank fifth on the CDC's list of the leading causes of death.
"Alzheimer's disease and other dementias are under-reported on death certificates and medical records," Dr. James said in a press statement. “Death certificates often list the immediate cause of death, such as pneumonia, rather than listing dementia as an underlying cause."
Keith L. Black, MD, professor and neurosurgery department chair at Cedars-Sinai Medical Center in Los Angeles, said this study goes further than prior ones in expanding on the broad impact of Alzheimer's.
It "... brings into focus the impact Alzheimer's disease has on our population as our life expectancy continues to increase," Dr. Black, also director of the Johnnie L. Cochran Jr. Brain Tumor Center and Maxine Dunitz Neurological Institute, told dailyRx News. "While prior research has pointed to the rising number of patients with the disease and the economic and emotional stress it has on caregivers, this research reveals a significant under-reporting of deaths from Alzheimer's disease as well as it being, potentially, the third leading cause of death in people over 65."
Dr. James and his research colleagues noted that an estimated 5 million US residents have Alzheimer's, and that some people with dementia have not been medically diagnosed with dementia.
Knowing the extent of Alzheimer’s deaths could raise awareness of that form of dementia and help researchers decide whether to prioritize scientific investigations of Alzheimer’s, Dr. James added.
This study was published online March 5 in Neurology.
The National Institute on Aging and Illinois Department of Public Health funded the study.
These six researchers included paid consultants to pharmaceutical companies and healthcare facilities and a paid faculty member at the Parkinson's Disease Foundation Learning Institute.