Tuesday July 7 2009
The study was in mice with a disease similar to Alzheimer's
Researchers say that “three large cups of coffee a day could help to slow the progress of Alzheimer’s disease and even reverse the condition”, The Times said. Several other newspapers also reported on a study in mice, which suggests that a daily dose of caffeine may suppress the degenerative processes in the brain that lead to impaired cognitive function.
Firstly, this study is in mice, so the results may not be applicable to humans. Some of the newspapers rightly caution that these findings do not mean that dementia patients should start using caffeine supplements or drink large amounts of coffee. Dementia is more common in the elderly, in whom there may be a number of reasons why a high caffeine intake would be particularly inadvisable, including high blood pressure and drug interactions.
The researchers say that “based on the robust protective and treatment effects of caffeine” observed, they have “initiated clinical trials with caffeine”. The fundamental message in this story is that more research is needed, i.e. studies that examine the effects of caffeine in people with Alzheimer’s disease.
Where did the story come from?
Dr Gary Arendash and colleagues from the University of South Florida, Saitama Medical Centre and Saitama Medical University in Japan and other academic institutions in the US carried out this study.
The research was funded through grants to individual authors from the Florida Alzheimer’s Disease Research Centre, and through funds from the Byrd Alzheimer’s Centre and Research Institute.
It was published in the peer-reviewed Journal of Alzheimer’s Disease.
What kind of scientific study was this?
This laboratory study assessed the effects of a diet supplemented with caffeine in mice with cognitive impairment caused by an Alzheimer’s-like disease. The researchers added caffeine to the drinking water of 18 to 19-month-old mice with impaired working memory for four to five weeks, then compared the effects with no caffeine supplements.
The researchers discuss some studies in humans, which suggest a link between daily caffeine intake and cognitive function or decline. They say that these studies cannot establish conclusively that caffeine is the causal factor because of the complex relationship between this and other environmental factors and lifestyle choices. The researchers say that their animal study may help to isolate the effects of caffeine intake from these other factors.
The researchers say that they demonstrated in a previous study that long-term caffeine supplementation reduced the development of brain plaques in mice prone to an Alzheimer’s-like disease. This study focused specifically on whether caffeine has an effect on aged mice “already exhibiting cognitive impairment”. The experiments compared the effects of caffeine with no caffeine. Further experiments were carried out in normal mice that were given caffeine to see whether they had cognitive benefits from life-long caffeine intake.
Fifty-five mice were included in the study. Mice were tested on various tasks to compare the effects of caffeine on cognition. The mouse brains were also extracted for examination.
The daily dose of caffeine given to the mice was equivalent to a human drinking 500mg a day, or about five cups of coffee. Control mice had access to as much untreated tap water as they wanted.
What were the results of the study?
The study found that after four to five weeks of daily caffeine, mice that had memory problems at the beginning of the study had less cognitive impairment. Overall, cognitive performance was significantly improved by caffeine. There were no cognitive improvements in mice that were not given caffeine.
There was no difference between the groups in non-cognitive tests that assessed anxiety and sensorimotor skills. Examination of the mice' brains revealed reduced levels of amyloid-β, the protein linked to cognitive decline in Alzheimer’s patients. Caffeine did not benefit normal mice without cognitive impairment.
What interpretations did the researchers draw from these results?
The researchers conclude that this is the first study to show that caffeine treatment can reverse cognitive impairment in mice with Alzheimer’s-like disease. They say that caffeine supplementation restored working memory in aged, cognitively-impaired mice to the level of normal, aged mice. They say the effect is likely to be caused by a reduction in brain amyloid-β production, following treatment.
What does the NHS Knowledge Service make of this study?
Experiments that simulate human disease in animals, such as the disease in this study, are often used for gaining a better understanding of how diseases work and to test potential new treatments in the early stages. However, given the obvious physiological and metabolic differences between humans and mice, the experiments can only give an approximate idea of the effects in humans.
This is very early research, and it is potentially dangerous to suggest that drinking large amounts of caffeine reverses the effects of a neurodegenerative disease such as Alzheimer’s. This disease is more common in the very elderly who for a number of reasons, including hypertension and drug interactions, should be cutting down coffee intake rather than increasing it.
The researchers discuss the biological and physiological mechanisms behind their findings and the complex chemical pathways that are affected by caffeine. They say that “based on the robust protective and treatment effects of caffeine” that they observed, they have “initiated clinical trials with caffeine”. The important message in this story is that more research is needed, i.e. human studies that examine the effects of caffeine on human systems.