A study published in Alzheimer’s Research & Therapy has shown that low-dose aspirin affects Alzheimer’s disease and vascular dementia only in the presence of coronary heart disease.
A well-known preventative
Acetylsalicylic acid, more commonly known as aspirin, is often taken at a steady, low dose of 100 to 300 milligrams a day in order to protect against cardiovascular diseases [1]. It is a non-steroidal anti-inflammatory drug (NSAID), which places it in a class of drugs that are often sold over-the-counter as pain relievers. However, aspirin in particular has been well documented in its positive effects on vasculature, particularly when taken over the long term.
Previous research has shown that long-term aspirin might be effective against Alzheimer’s disease and vascular dementia [2], but only when given over a very long time period. Two other studies excluded patients with cardiovascular disease, and these studies did not show significant results. As cardiovascular events are linked to cognitive decline [3], the researchers of this study sought to determine if this was the defining factor in aspirin’s effectiveness against dementias.
Two different cohorts
To better ensure that their results would apply to multiple populations, the researchers applied their analysis to two different cohorts: the German ESTHER cohort and the UK Biobank. Over 5,000 people in ESTHER and more than 300,000 people in the UK Biobank were eligible to be analyzed in this study. Because of the different nature of these cohorts, exclusions, such as for pre-existing dementia, could not be processed in the same way.
The results were clear. The use of low-dose aspirin for over ten years, in people with a history of coronary heart disease, made them much less likely to get Alzheimer’s disease, vascular dementia, or all-cause dementia than people with this same symptom who did not take low-dose aspirin.
Interestingly, this strong signal was only found in the ten-year group. Participants who had taken low-dose aspirin for more than five years but less than ten years did not enjoy statistically significant benefits. People who did not have coronary heart disease also did not significantly benefit from this treatment.
Conclusion
Discussing their results, the researchers note some limitations regarding this study, many of which apply to such cohort studies more generally. There was no placebo group. People who take long-term, low-dose aspirin often begin taking it after a diagnosis of coronary heart disease or some other cardiovascular disease, which, of course, is a risk factor for dementia. The researchers accounted for this fact in their proportional hazard model, and it is also the reason they excluded people who have been taking low-dose aspirin for less than five years.
In total, the evidence seems fairly conclusive that any effect that aspirin may have against Alzheimer’s disease and vascular dementia is primarily due to its well-known effects against cardiovascular diseases. While there may be some biochemical effects, the researchers hypothesize that instead of having much of an effect against Alzheimer’s itself, low-dose aspirin could be decreasing the apparent symptoms of Alzheimer’s disease largely due to its influence on vascular dementia, which frequently accompanies Alzheimer’s. This phenomenon is known as mixed dementia [4].
These results, while disappointing for people looking for an anti-inflammatory treatment for Alzheimer’s, open the door to another line of questioning: how much is there to be gained by focusing on vasculature when looking for ways to reduce dementia? If low-dose aspirin’s effects can be replicated with a drug that shows effects in less than ten years, it may prove useful in keeping people healthier for longer.
Literature
[1] Smith, S. C., Benjamin, E. J., Bonow, R. O., Braun, L. T., Creager, M. A., Franklin, B. A., … & Taubert, K. A. (2011). AHA/ACCF secondary prevention and risk reduction therapy for patients with coronary and other atherosclerotic vascular disease: 2011 update: a guideline from the American Heart Association and American College of Cardiology Foundation endorsed by the World Heart Federation and the Preventive Cardiovascular Nurses Association. Journal of the American college of cardiology, 58(23), 2432-2446.
[2] Breitner, J. C., Baker, L. D., Montine, T. J., Meinert, C. L., Lyketsos, C. G., Ashe, K. H., … & ADAPT Research Group. (2011). Extended results of the Alzheimer’s disease anti-inflammatory prevention trial. Alzheimer’s & Dementia, 7(4), 402-411.
[3] Xie, W., Zheng, F., Yan, L., & Zhong, B. (2019). Cognitive decline before and after incident coronary events. Journal of the American College of Cardiology, 73(24), 3041-3050.
[4] Custodio, N., Montesinos, R., Lira, D., Herrera-Pérez, E., Bardales, Y., & Valeriano-Lorenzo, L. (2017). Mixed dementia: A review of the evidence. Dementia & neuropsychologia, 11, 364-370.
