By Chelsea Arent and Brooke Palay
Do you struggle to stay alert and focused all day? Are you struggling to get enough sleep? If so, you’re not alone. Unfortunately, as we age sleep quality and total sleep time decreases, so tiredness may only get worse (13). Therefore, many people turn to either a short nap or a cup of coffee. But, is one of those options better than the other, and what are the long-term effects on your brain? Let’s look at this scientifically…
First Things First
Some studies do show that both daytime naps and coffee can improve cognitive health. Here’s the quick comparison:
COFFEE. Many studies suggest that coffee may protect cognitive function. Perhaps the best example is a study from Finland, which found that midlife coffee drinking was associated with a lower risk of Alzheimer’s disease and dementia later in life (6). This study followed 1,409 individuals over 21 years, and researchers measured participants’ coffee consumption and cognitive health at the beginning and end. Remarkably, moderate coffee drinkers (three to five cups per day) were 65-70% less likely to develop cognitive dysfunction (and brain diseases like Alzheimer’s) compared to those who didn’t. In general, this is consistent with other studies showing that regular coffee consumption lowers your risk for age-related cognitive impairment.
NAPPING. Studies on napping also suggest a cognitive benefit. Researchers in Australia found that naps shorter than one hour provide the most protection against cognitive decline. These researchers measured napping habits and cognition over 10 years in 2,012 individuals over age 65. The risk for cognitive problems in nappers was 38% lower after two years and 48% lower after 10 years. Those nappers were also 67% less likely to score poorly on a test of cognitive function called the Mini Mental State Examination (MMSE), which is a common questionnaire doctors use to check cognitive health. These findings are consistent with other studies suggesting that daytime naps improve working memory and learning ability (5,7), and it’s probably at least partly because the majority of memory consolidation occurs during sleep (meaning sleep helps solidify the things you learn throughout the day). Without sleep, we’d be a lot more forgetful.
Which Is Best?
Both a nap and a cup of coffee will help get you through the day, but is one better than the other for long-term brain health?
This question is important for aging adults all over the world. Cognitive function starts to decline even in middle age, and after age 65, the risk of developing neurodegenerative diseases like Alzheimer’s increases greatly—so any choice that protects your brain is a good one. To address this issue, we systematically reviewed scientific studies on coffee, daytime naps and long-term cognitive function in middle aged and older adults (see “Review Methods” at the end of this article for details). Most of the studies we found were observational and longitudinal—following nappers and coffee drinkers over time and assessing their brain health. Here’s what the studies show:
A Closer Look at the Evidence
NAPPING. As you can see in the table above, there have been four studies on napping and cognitive function. One study followed nappers over time, two studies took snapshots of cognitive health in current nappers, and one study asked adults with Alzheimer’s disease to recall their past napping habits. No studies have randomly assigned people to be “nappers” or “non-nappers” and followed their brain health over time (a randomized-controlled trial). This type of trial would be ideal because it would account for other variables that might influence results. For instance, some people take naps due to underlying conditions that might also affect brain health.
That being said, most of the existing studies are promising. In fact, only one of the four studies looks bad for nappers (4). In that study, those with mild cognitive impairment (MCI) napped on average one extra day compared to those with no impairment, but overall cognition did not differ between nappers and non-nappers. This study was fairly small (only 133 subjects), so it’s not convincing—especially because the other three napping studies suggest that naps either shorter than one hour, or naps one to two times a week, result in higher MMSE scores or a lower dementia risk (1,3,9). The most compelling evidence is from two of these studies—both in more than 2,000 subjects. Together, the studies suggest that one to two naps shorter than one hour per week provide the most protection against dementia (3,9).
COFFEE. Eight studies have focused on the long-term effects of coffee consumption, and four showed that coffee drinkers have a lower risk of developing cognitive/brain disorders. In one example, Italian researchers looked at regular coffee drinkers and the risk of MCI. They found that coffee drinking generally put them at lower risk for developing MCI, but interestingly, individuals who consumed more than two cups a day actually had a higher risk (14). Another study in an elderly Japanese population (more than 13,000 people) found that coffee consumption was associated with a lower risk of dementia, and the relationship was even stronger in women, nonsmokers, and those who did not consume alcohol (15). These are just two examples, but the point is that there is substantial evidence that regular coffee drinking may lower the risk of MCI, dementia, or Alzheimer’s.
How much coffee does it take? Well, again, most of this is observational evidence (meaning, it’s not from randomized controlled trials), so we can’t be certain about cause and effect. It’s also hard to say how much coffee you need to drink and for how long. The number of subjects in these studies ranged from 500 to more than 13,000, and the study length varied from 3.5 to 28 years. The amount of coffee consumed also varied greatly—ranging anywhere from zero to five cups per day. Because of this, there is no clear pattern. However, what we can tell you is that the most convincing study tested 13,137 subjects and showed that drinking a moderate amount of coffee (three to five cups per day) was associated with a 65-70% reduction in the risk for dementia and a roughly 63% reduction in the risk of Alzheimer’s (6). This was an observational study, but this and the other research generally point to a magic number for length of naps (less than one hour) and cups of coffee (three to five) per day.
Take Your Pick
Let’s recap. We know that sleep quality decreases as you age, making a daytime nap or a cup of coffee a daily necessity for many Americans. The evidence on how both coffee and naps affect cognitive function is not perfect; neither is supported by randomized controlled trials, so more research needs to be done in this area. What we can say is that neither will increase your risk of dementia, and most of the observational data for both look promising, so it’s probably best to consider your lifestyle and pick the habit that is best for you.
ABOUT THE AUTHORS
Chelsea Arent and Brooke Palay 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 systematic review, the authors searched the biomedical research database PubMed using the following two searches: “(caffeine OR coffee) AND (cognitive OR cognitive functioning OR cognitive decline OR dementia) AND adults” and “(nap OR napping OR naps OR daytime nap OR diurnal sleep) AND (cognitive OR cognitive functioning OR cognitive decline OR dementia) AND adults.” The flow charts below show the authors’ inclusion/exclusion criteria and results for coffee (left) and napping (right).
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