By Lindsey Reinmuth and Hailey Lynch
Are you addicted to coffee? Based on the number of Starbucks around the world (24,000 stores in 70 countries), one could say humans love their caffeine. Most people drink it as an early morning pick-me-up, a stimulant to stay awake, or as liquid “productivity fuel.” However, these examples all highlight the short-term effects of caffeine, such as improved attention and concentration. But how does long-term consumption affect all those coffee lovers?
As it turns out, you and the other 83% of adults who consume caffeine could be getting more health benefits than you think. For example, a recent New York Times article mapped out many benefits of coffee, which include lower rates of cardiovascular disease, stroke, overall cancer incidence, type 2 diabetes, and liver disease.
But what about the brain? Cognitive function (including memory, problem-solving speed, etc.) tends to decline as we age, which increases our risk for neurodegenerative/brain diseases and conditions like dementia. Because this is a rapidly increasing health concern in aging adults, we set out to determine if caffeine (coffee) consumption might have some long-term cognitive benefits. To do this, we focused on whether or not caffeine can prevent cognitive declines and, if it does, how much (how many cups of coffee per day) produces the best results.
In order to determine what makes this chemical in your dark brown water so special, we systematically searched some scientific databases, such as Google Scholar and PubMed, for studies that include terms like “caffeine,” “cognitive function,” and “cognitive impairment.” Then, to specifically address the question of prevention, we focused on studies with healthy subjects younger than 80, and we made sure the studies were at least three years long. For more information on how we conducted this review, see the “Review Methods” section at the end of this article.
What Does the Science Say?
We found 10 studies that met our criteria. Of these, eight reported that caffeine consumption is associated with a reduced risk for cognitive impairment, including some neurodegenerative diseases. Now that is something to buzz about! Some studies are so convincing, they could make anyone run to the nearest coffee shop, but there’s always more to the story. Let us explain.
The 10 studies—compared below—are somewhat similar. Typically, the researchers identified people who met their criteria, followed them over a certain period of time, and then documented how much caffeine (coffee) they drank during that time and how many people developed brain-related problems.
Several studies focused on cognitive impairment, which is not only prevalent within the United States, but also all over the world. For example, a 10-year study of 676 healthy men from Finland, Italy, and the Netherlands found that men who consumed three cups of coffee per day had an approximately 4.3 times smaller decline in cognitive function than non-consumers (Van Gelder et al., 2007). Interestingly, three cups per day was the sweet spot: cognitive decline over the 10 years was somewhat worse in those who consumed four or more cups per day (although still better than none). These results show that moderate amounts of coffee may have a protective effect on long-term cognition.
Many of the other studies focused on neurodegenerative diseases. For example, one of the most common diseases associated with cognitive impairment is Alzheimer’s disease (AD). In one study that included 1,409 subjects (ages 65-79), researchers randomly selected participants from the “Cardiovascular Risk Factors, Aging, and Dementia Study” (a large, ongoing research study in Finland) and followed up with them 21 years later (Eskelinene et al., 2009). After that time, 61 people were identified as having dementia or AD (about 4% of the subjects, which is similar to the approximately 5-7% of people in the general population of older adults with AD or dementia). However, subjects who drank three to five cups of coffee per day had a 65% lower risk of cognitive impairment and AD compared to those who drank little or no coffee.
Besides AD, another common neurodegenerative disease is Parkinson’s disease (PD). Even though many people think of PD as a movement disorder, the death of brain cells is what impairs muscle movement in this disease. In a study from 2001, researchers examined caffeine and coffee consumption in 47,351 men and 88,565 women enrolled in several long-term studies in the United States (Ascherio et al., 2001). After a long follow-up period (10 years in men, 16 years in women), researchers found that men who consumed the most coffee were as much as 58% less likely to develop PD, and interestingly, women’s optimal risk reduction came with one to three cups of joe per day (more cups actually increased risk). So, regardless of your gender, this study suggests moderate coffee consumption just might be a good part of your daily routine for keeping brain function intact.
Are all these benefits of coffee too good to be true? Well, all of the studies mentioned above were observational. That is, the researchers didn’t randomly assign people to coffee or no coffee, so we can’t be certain that the coffee/caffeine is what reduced the risk. Also, while they are in the minority, we did find two studies that suggest coffee may not be as great as it seems. One study examined the association between drinking coffee and cognitive performance with aging (Laitala et al., 2009). The study consisted of telephone questionnaires of 2,606 Finnish twins before and after a 28-year period, and results showed that coffee consumption had no effect on the risk for cognitive impairment or dementia. Although telephone interviews are usually less objective, these findings are supported by another study that found no association between coffee/caffeine intake and the risk of dementia or cognitive impairment (Gelber 2011).
So What Does This All Mean?
Although caffeine is found in many other foods and beverages, coffee is one of the most commonly consumed beverages on the planet. Because eight out of the 10 studies we found suggest a reduced risk for cognitive impairment or diseases, coffee may be more than just a shot of caffeine. Most of these studies also found a similar number of cups of coffee that seems to maximize protection (two to three per day, but not more than five). These results are promising, and with the prevalence of brain/cognitive disorders on the rise and no present cure, having a cup or two of coffee a day seems like a good solution, right?
Well, maybe not: Because of the few studies we found that showed conflicting evidence, and because all of these studies were observational, we cannot be 100% sure that long-term coffee/caffeine consumption protects your brain. Ideally, what we would like to see is a trial in which researchers randomly assign large groups of people to drink either two to three cups of coffee or two to three cups of something else without caffeine each day, follow them over time, and determine if the caffeine/coffee drinkers actually have better cognitive function. Will that trial ever happen? Who knows, but in the meantime, we can at least say that the observational evidence is pretty compelling. So, if you already religiously drink coffee, be sure to thank your addiction, because you could be getting more benefits in the future than expected. However, if you don’t already drink coffee or simply don’t like the taste, don’t sweat it—that just means there’s more for the rest of us!
ABOUT THE AUTHORS
Lindsey Reinmuth and Hailey Lynch are students in the Integrative Physiology Department at the University of Colorado Boulder. This paper was peer reviewed by scientists at CU Boulder.
To conduct this scientific review, the authors searched PubMed with the search terms “(caffeine OR coffee) AND (cognitive impairment OR cognitive function OR cognition).” They restricted the results to studies in human subjects, which gave them 160 results. From there, they set the age limit to adults younger than 80 years old, which narrowed the results to 135. The authors then combed each result to identify those that lasted three years or more (to effectively measure long-term effects) and included only cognitively healthy subjects. This resulted in a total of 10 studies.
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