This is the first in our new series of blog posts looking into current and past scientific research and scientific concepts that are often misinterpreted or generally misunderstood. The goal of this blog series is for us as scientists and writers to struggle through articles and research so that you don’t have to. If you have a science news piece you’ve read, a concept you want to know more about, or general science questions, email them to firstname.lastname@example.org and you might see your topic in a blog post!
To begin our new blog series, I wanted to talk about this article that I came across recently on Facebook. It was posted by a neuroscience research page that I follow, and also it’s about tea. I ADORE tea (and neuroscience), so of course I had to read it and subsequently tell the world about it.
The gist of the article is that drinking tea every day may help fend off cognitive decline as we get older and decreases the risk of developing dementia and Alzheimer’s disease. If this is true, then this is HUGE. Alzheimer’s Disease is a devastating neurodegenerative disease that affects a lot of people and comes with some pretty severe memory, mood, and physical issues. As someone who has had a family member die from Alzheimer’s Disease, I’m always on the look out for research that has found a cure. As a neuroscientist, though, I’m always skeptical.
So let’s look a little more closely at the research that this article is citing. First, I went to the original National University of Singapore news release (found here). It begins, “A cup of tea a day can keep dementia away,” (what a freaking amazing first sentence, am I right?) before proceeding to describe the study and how drinking tea every day can lower the risk of cognitive decline in older age. This is pretty similar to the article that cited it–similar enough to make me question how plagiarism works in the news.
At this point I’m reaching for my tea kettle, partly because I adore tea but also partly because I don’t want to develop Alzheimer’s Disease. But then I realized that as a skeptic I should probably go to the original article to see what’s up.
I realize not everyone has access to articles the way I do because I’m a graduate student and my university pays an enormous amount of money for access to academic journals. I don’t know how illegal it is for me to share the PDF, but here it is if you’re interested and please no one report me to the feds: Tea consumption reduces the incidence of neurocognitive disorders: Findings from the Singapore longitudinal aging study (a catchy title, I know). If reading academic articles makes your brain hurt, you’re not alone. In theory I’ve been doing this for years and should be able to understand many types of academic articles well enough to breeze through them. In practice, different fields of science have such vastly different ways of describing their experiments, peppered with mass quantities of jargon and–god forbid–mathematical models specific only to that field. So don’t worry, I’ve already struggled through it for you and here’s what it says and what I thought:
What they did: 957 Singaporeans 55 years or older participated in this study. They had normal cognitive functioning between 2003-2005 (measured through something called the Mini Mental State Exam, which is legit according to my clinical psychologist friends). During those years, participants answered questions about their tea drinking habits: how often did they drink tea and what type of tea did they drink? The options for types of teas were “Ceylon/English” tea aka black tea, “Chinese tea” which I think is oolong, and “Green” tea which–correct me if I’m wrong–refers to green tea. They also asked for gender (male or female, in this case) and whether participants had a specific allele of a gene that is a risk for developing Alzheimer’s disease (an APOEε4 gene, if you’re interested). Finally, they looked at incidence of developing a “neurocognitive disorder” such as Alzheimer’s disease between 2006 and 2010 (72 of the participants fell into this category). They controlled for a bunch of variables, too, like BMI, whether people smoked, education, age, etc, to try to only be looking at the effect of tea.
What they found: This is where it gets cool. They did some magic stats (not really, they did some two-sided Chi-square tests and logistic regression models) where they looked at whether drinking tea was associated with a lower incidence of neurocognitive disorders at their later time point. They did this first with just tea as their comparison and then also while controlling for a bunch of other variables (education level, alcohol consumption, physical activity, etc.) that also might have an effect on cognition. They partly control for other variables because they want to make sure they’re testing JUST FOR TEA, but also because their groups had some baseline differences in these measures so we need to put them into our statistical models in an effort to say, “if I hold this constant, does tea still have an effect.”
Guys, it totally does. They found that the group with consistent tea consumption throughout the experiment (can be black, oolong, or green) had a much lower incidence of neurocognitive disorders (aka percentage of people who developed neurocognitive disorders) later on. This protection, however, is ONLY for women and maybe also (but the stats aren’t sure) for people with that APOE risk allele we talked about earlier. So men without an APOE risk gene, you don’t have extra protection (but good job on not having a risk allele, I guess?) but can still enjoy tea for it’s other helpful properties like attention or alertness.
So ladies (and everyone with an Alzheimer’s risk allele), go forth and buy tea.
Let’s talk about how to look at this paper critically. I’ll go through just a few of my thoughts (not all of them but some). First, there were some big baseline differences between tea drinkers and non-tea drinkers in 2003-2005. Does this mean these two groups of people are fundamentally different other than their tea drinking? Are there separate factors that drive both tea drinking AND a lower chance of neurocognitive disorders? Maybe. Science is hard and we can’t always control for every little thing. These guys actually did a pretty good job with what they had to work with. I’ll give them the benefit of the doubt.
Also, what about white tea? I love me some white tea and I keep hearing about how good it is for you. How am I supposed to know if these claims are real if science doesn’t include it? I assume it wasn’t included because white tea isn’t as prominently imbibed in this participant pool. Still would have loved to see it.
Finally, and they say this in their discussion section, statistical power is better with more participants, and they didn’t have as many as they wanted in some of their groups (like green tea only drinkers) which makes it hard to say for sure whether this is real or whether it’s by chance because we have a small population. It’s a pretty big group of people and the oolong/black tea group is definitely large enough to show support for tea drinking, but to be certain it would be nice to see more participants in the future.
Let me start by just saying that tea is delicious and cozy and perfect so you may as well drink a cup every day. But also tea may or may not decrease your risk for developing a neurocognitive disorder when you get older. So, best casenario, you fend off dementia. Worst casenario, you drink delicious tea your whole life.
I’m hoping to see future studies looking at the underlying reasons for this protective effect. They mention the components of tea that they think are at play, but, you know, I want to see concrete evidence and all that jazz.