“Individuals with SDB (sleep-disordered breathing) commonly report problems with cognition and may be at increased risk for dementia. Our results suggest that more severe overnight hypoxemia and sleepiness may be related to poorer cognitive function, especially attention, concentration, and process speed in middle-aged to older adults, and that the risk is greater among carriers of APOE, a known risk factor for Alzheimer's disease,” study author Dr. Dayna Johnson said.
People who were at-risk of developing Alzheimer's had in them a gene known as apolipoprotein ?4 (APOE-?4) allele, which transports cholesterol and facilitates brain injury repair in healthy people. Around 20 percent of the people in the United States likely carry the APOE-?4 allele, while 40 percent of Americans likely snore while sleeping, the study said.
“With use of this type of information, future risk stratification may help to identify individuals at increased risk for SDB-related cognitive effects,” Dr. Johnson said.
How the study was conducted
Around 1,752 people with an average of 68 participated in a sleep study. For each participant, the researchers calculated the:
- Apnea-hypopnea index (AHI), which measures how many apnea or hypopnea episodes a person has per hour of sleep, and the
- Percentage of time during sleep when their blood contained oxygen levels below 90 percent.
The researchers then tested the participants' cognitive abilities via assessing these three areas:
- Overall brain function, including attention and focus,
- How fast the brain could grasp data and perform tasks (processing speed), and
- Memory and attention using the Digit Span Test.
Aside from the Harvard Medical School in Boston, Massachusetts, the study was conducted by experts from the Wake Forest School of Medicine in Winston-Salem, North Carolina; the National Institute for Occupational Safety and Health; Stanford University School of Medicine; Brigham and Women's Hospital; Beth Israel Medical Deaconness Center; University of Washington; and the U.S. Centers for Disease Control and Prevention.
The study analyzed data from the ongoing Multi-Ethnic Study of Atherosclerosis, which identified how various lifestyle factors impacted the risk of developing atherosclerosis. (Related: Alzheimer's is really just 'type-3' diabetes, new research shows.)
The study, however, did not go on to further examine if the people who are predisposed to develop dementia because of sleep apnea and other sleep conditions really did get afflicted with Alzheimer's in their old age. It also concluded that as far as factors go, having sleep apnea or other conditions has but a minimal effect to the chances of actually being susceptible to mental decline, England's National Health Services said in a statement.
An unlikely ally against cognitive decline: strawberries
A study that was conducted earlier this month showed that strawberries could help deter the onset of age-related cognitive decline. Strawberries contained a compound called fisetin, which eases mental degradation in the mice that it were exposed to it. The mice that were not treated with this compound suffered from inflammation and cognitive difficulties, researchers said.
According to Pamela Maher, senior author and senior staff scientist at Salk's Cellular Neurobiology Laboratory in La Jolla, California, “Mice are not people, of course. But there are enough similarities that we think fisetin warrants a closer look, not only for potentially treating Alzheimer's disease but also for reducing some of the cognitive effects associated with aging, generally.”
Read up on more stories such as this one at Alzheimers.news.
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