Alzheimer's disease is associated with memory-related problems. It is characterized by neuropsychiatric symptoms found in the early stages. Long-term use of caffeine is found to alter these neuropsychiatric symptoms in patients with Alzheimer's disease.
The neuropsychiatric symptoms include behavioral and psychological symptoms of dementia (BPSD), anxiety, apathy, hallucinations, paranoid and sundowning.
Coffee or caffeine has recently been suggested as a strategy to prevent dementia, both in patients with Alzheimer's disease and in normal aging processes, due to its action in blocking molecules - adenosine receptors - which may cause dysfunctions and diseases in old age. However, there is some evidence that once the cognitive but also the NPS symptoms are developed, caffeine may exert opposite effects.
"We had previously demonstrated the importance of the adenosine A1 receptor as the cause of some of caffeine's adverse effects. Now, we simulated a long oral treatment with a very low dose of caffeine (0.3 mg/mL) equivalent to three cups for a human coffee-drinker to answer a question which is relevant for patients with Alzheimer's, but also for the aging population in general, and that in humans would take years to be solved since we should wait until the patients were aged' - explains Dr Björn Johansson, researcher and physician at the Karolinska University Hospital. The research was conducted from the onset of the disease up to more advanced stages, as well as in healthy age-matched mice.
The results indicate that caffeine alters the behavior of healthy mice and worsens the neuropsychiatric symptoms of mice with Alzheimer's disease. The researchers discovered significant effects in the majority of variables studies, especially in relation to neophobia, a fear of everything new, anxiety-related behaviors, and emotional and cognitive flexibility.
In mice with Alzheimer's disease, the increase in neophobia and anxiety-related behaviors exacerbates their BPSD-like profile. Learning and memory, strongly influenced by anxiety, got little benefit from caffeine.
"Our observations of adverse caffeine effects in an Alzheimer's disease model together with previous clinical observations suggest that an exacerbation of BPSD-like symptoms may partly interfere with the beneficial cognitive effects of caffeine. These results are relevant when coffee-derived new potential treatments for dementia are to be devised and tested", says Dr. Lydia Giménez-Llort, researcher from the INc-UAB Department of Psychiatry and Legal Medicine and lead researcher of the project.
The results of the study form part of the Ph.D. thesis of Raquel Baeta-Corral, first author of the article, and are the product of a research led by Lydia Giménez-Llort, Director of the Medical Psychology Unit, Department of Psychiatry and Legal Medicine and researcher at the UAB Institute of Neuroscience, together with Dr Björn Johansson, Researcher at the Department of Molecular Medicine and Surgery, Karolinska Institutet and the Department of Geriatrics, Karolinska University Hospital, Sweden, under the framework of the Health Research Fund project of the Institute of Health Carlos III*.