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Moderate Coffee Intake Linked to Lower Dementia Risk
More than 7 million Americans live with Alzheimer's disease. And that number will grow dramatically. Worldwide, there is already a massive burden from all types of dementia. And our treatments for these diseases are very limited. Although the newest U.S. Food and Drug Administration (FDA) approved medications for treating dementia are somewhat effective, they do not halt the progression of the disease; they are expensive; and they carry significant side effects.
Therefore, prevention of dementia is essential. Any modifiable daily habit that decreases a person's risk for developing dementia could have major public health implications. Coffee has been talked about for a while as possibly being a protective agent against dementia, however, the evidence has been inconsistent until now. A new long-term study helps clarify this.
Why does this matter?
Dementia takes years to develop. This makes it difficult to conduct studies. Therefore, we can't use small studies that last for a short period of time to answer questions. In order to get valid results, researchers need large numbers of participants who are followed for extended periods of time (usually many years), and they need to assess the participant's habits (such as coffee intake) multiple times during the study.
This new study is unique. It followed over 130,000 participants from two large cohort studies for up to 43 years. Participants were asked about their coffee intake every 2 to 4 years.
A study like this can't definitively prove causality. However, it is significantly better than most of the single snapshot studies of diet that make up most of the nutrition headlines.
What did the study find?
The researchers looked at the incidence of diagnosed dementia and earlier signs of cognitive decline. During the study, approximately 11,000 of the participants were diagnosed with dementia.
Participants were grouped by their coffee intake. When compared to those who drank no coffee, the following associations were seen:
- Those who drank less than one cup of coffee per day had a slightly lower (about 2%) risk of developing dementia.
- Those who drank one to 2.5 cups of coffee per day had a lower (approximately 19%) risk of developing dementia.
- Those who drank 2.5 to 4.5 cups of coffee per day had a lower (approximately 18%) risk of developing dementia.
Overall, the data suggested that moderate coffee consumption was associated with the largest decrease in dementia risk, although the curve flattened at higher levels of intake rather than continuing to drop.
In practical terms, the signal for the best benefit was strongest in the area of 2 to 3 cups of coffee per day.
Coffee may matter before dementia develops
The researchers didn't only evaluate formal dementia diagnoses. They also evaluated early signs of cognitive decline using self-reported changes in memory and cognition and performance testing.
Similar patterns were observed among coffee intake levels. Higher coffee consumption was associated with fewer self-reported cognitive issues.
It doesn't necessarily mean that coffee will prevent early cognitive decline, but it suggests that the relationship might exist prior to a formal dementia diagnosis.
The decaf finding was particularly noteworthy
One of the more unexpected findings of this study was that decaf coffee did not appear to be associated with the same apparent level of protection. This raises the possibility that caffeine may be an important component of the association.
There are several possible reasons why this could occur, but all of them are purely speculative:
- Caffeine blocks adenosine receptors, which may be involved in processes related to neurodegenerative disorders.
- Caffeine may reduce inflammation in the brain.
- Caffeine may enhance insulin sensitivity, and metabolic dysfunction is linked to dementia risk.
- Coffee and tea also contain polyphenols and other compounds that may protect against oxidative stress and promote vascular health.
At this stage, the mechanism remains unknown. The study suggests that caffeine may be important, but does not provide insight into why.
Important limitations
Although this study was a long-term, observational study, it was still an observational study. Therefore, it cannot demonstrate whether or not coffee reduced the risk of dementia.
The researchers accounted for many potential confounders such as demographics, lifestyles, and diet quality. However, it is always possible that there are some residual confounds. For example, coffee drinking may be correlated with certain behaviors or characteristics that may partially account for the findings.
Additionally, there are important limitations to generalizing beyond coffee and tea. While it is possible that caffeine may contribute to the observed association, this does not suggest that other caffeinated beverages (i.e., energy drinks) that have very different nutritional profiles would produce the same effects.
What does this mean in real life?
If you already consume coffee, this study provides evidence that moderate amounts of coffee are likely compatible with maintaining healthy brain function over the long term, and possibly even having a protective effect. The most beneficial amount in this study was roughly 2 to 3 cups of coffee per day.
A few additional practical considerations are worth noting:
- Moderate amounts of coffee should be considered preferable to excessive consumption. There is no indication that greater amounts are superior to moderate amounts.
- Avoid consuming coffee in the evening if it negatively impacts your ability to fall asleep. Maintaining quality sleep is a critical aspect of maintaining long-term brain health, and the relationship between sleep and dementia risk is discussed in how to optimize your sleep for better health.
- Refrain from adding large amounts of sugar and cream to coffee.
- Preferentially choose filtered coffee. Unfiltered coffee can increase LDL cholesterol. For more information regarding cholesterol and cardiovascular disease risk, see what science says about saturated fat and heart disease.
Why sleep is particularly important here
Even if people believe that caffeine does not impact their sleep, it can still negatively affect sleep quality. Sleep quality is an important aspect of brain health and dementia risk.
What this study does NOT mean
This study does NOT mean that coffee is a sure-fire way to prevent dementia. Additionally, this study does NOT replace the existing, well-established strategies to reduce risk.
The larger picture still includes:
- Blood pressure management
- Exercise
- Healthy sleep
- Metabolic health
- Not smoking
- Managing hearing loss, sleep apnea, etc. - all major risk factors.
While coffee may be a helpful piece of a broader prevention strategy, it is not a singular method of reducing risk.
Take-Aways
- Moderate coffee consumption may be associated with a decreased risk of dementia in the long run, according to a large long-term study.
- The strongest associations with lower dementia risk occurred in the range of 1 to 4 cups of coffee per day, especially 2 to 3 cups of coffee.
- Decaf coffee showed little to no protective effect.
- The mechanism is uncertain, however, it is plausible that caffeine may play an important role.
- Observational data cannot prove causation.
- Coffee should be consumed in a manner that does not interfere with sleep quality and overall dietary quality.
Summary
This study reinforces the theory that moderate coffee consumption may be associated with lower dementia risk in the long term. The effect was not linear, and more was not clearly better. The most beneficial relationships appeared in moderate coffee consumers and not in extreme coffee consumers.
The study had several advantages: it was large, long-running and continuously collected coffee consumption data for decades. However, it still cannot establish causality. The most reasonable interpretation is that moderate coffee consumption is compatible with brain-healthy habits, and may have a protective effect; particularly when caffeinated, filtered and consumed in the morning to avoid interfering with sleep quality.