A new study from a team led by researchers at the Johns Hopkins Bloomberg School of Public Health found that signs of common infections in a sample of middle-aged and older adults were associated with lower performance on a test of global cognitive function. .
The results add to a growing body of evidence suggesting that infections in midlife and old age may impair cognitive performance and may increase the risk of Alzheimer’s disease and other dementias.
For their analysis, the researchers examined antibody levels against five common pathogens in 575 adults, ages 41 to 97. Adults were recruited from East Baltimore in 1981, as part of the Epidemiologic Catchment Area Study initiated that year by the National Institute of Mental Health. . Participants in the Baltimore study donated blood for testing and took cognitive tests during the same study period. Antibody tests were performed for pathogens, including four herpes viruses (herpes simplex virus type 1, cytomegalovirus, varicella zoster virus (varicella and herpes zoster viruses), and Epstein-Barr virus) and the parasite toxoplasma gondii. The latter is often transmitted to humans through cat feces or by eating undercooked meat.
The research team compared the results of the participants’ blood tests with their performance on the Mini-Mental State Exam, a global cognitive test that assesses aspects such as orientation, attention, speech comprehension, memory and perception. visual, and in a word recall task, which tested memory for a list of words after a 20-minute delay. The researchers found that elevated antibodies to herpes simplex virus type 1 or cytomegalovirus were individually associated with poorer performance on the global cognitive test. In addition, participants with a greater number of positive antibody tests tended to miss a greater number of items on the global cognition test.
The study was published online April 7 in the journal Alzheimer’s and dementia.
“The idea that common infections could contribute to cognitive decline and perhaps Alzheimer’s disease risk was once sidelined and remains controversial, but because of findings like these, it is beginning to receive more attention.” says lead author Adam Spira. , PhD, Professor in the Department of Mental Health at the Bloomberg School and Senior Faculty Member of the Johns Hopkins Center on Aging and Health. “After accounting for the participants’ age, gender, race, and highest genetic risk factor for Alzheimer’s disease, data from our study showed that increased numbers of positive antibody tests were linked to five different infections was associated with poorer cognitive performance, this kind of additive effect of multiple infections on performance on a cognitive test has not been shown before.”
The cause of Alzheimer’s disease remains unclear. Previous research has established the connection to infections, including studies linking herpes simplex virus type 1 and cytomegalovirus with an increased risk of Alzheimer’s. There is also evidence that the protein fragment amyloid beta, which forms insoluble plaques in the brains of people with Alzheimer’s, functions as an antimicrobial peptide and is secreted at higher levels by brain cells in response to infections.
Since the 2003-2004 wave, the ACE study researchers at Johns Hopkins have conducted regular follow-up interviews in Baltimore, including standard cognitive tests and blood sampling. The two most recent waves of the study, funded by the National Institute on Aging, have focused on Alzheimer’s disease and related outcomes.
The pathogens tested in the study are often found in infancy and are shed or converted to suppressed latent infections. As such, the researchers considered significant levels of antibodies against them in the middle-aged and older study participants as likely indicators of their reactivation due to the weakening of the immune system with age.
The study’s first author, Alexandra Wennberg, PhD, who completed her doctoral training in Spira’s research group, is currently a postdoctoral research associate at the Karolinska Institutet in Sweden. Coauthors include professors from Johns Hopkins School of Medicine and collaborating scientists from the National Institute on Aging’s Intramural Research Program.
Co-author Brion Maher, PhD, a geneticist and professor in the Bloomberg School’s Department of Mental Health, also analyzed the results of participants who had a common Alzheimer’s risk factor, the Ɛ4 variant of the apolipoprotein-E (ApoE) gene. ). The link between positive antibody count and cognitive status was present in the Ɛ4 and nonƐ4 groups, but was stronger in the nonƐ4 group.
“It was a surprise to find a weaker link in the Ɛ4 group,” says Maher. “It’s something that needs to be followed up with larger studies.”
Spira, Maher and their team, with funding from the National Institute on Aging, are following up with analyzes of the Baltimore ACE data from the 2016 to 2022 wave. The researchers will also collect another round of data from this cohort.
The “Association of Common Infections with Cognitive Performance at Follow-up in the Baltimore Epidemiological Catchment Study” was co-authored by Alexandra Wennberg, Brion Maher, Jill Rabinowitz, Calliope Holingue, Ross Felder, Jonathan Wells, Cynthia Munro, Constantine Lyketsos, William Eaton, Keenan Walker, Nan-ping Weng, Luigi Ferrucci, Robert Yolken, and Adam P. Spira.
Funding was provided by the National Institute on Aging (R01AG075996, U01AG052445), the National Institute of Mental Health (MH 47447), and the Stanley Institute for Medical Research.
—————————————————-
Source link