UMAIR IRFAN: This is Science Friday. I’m Umair Irfan, in for Ira Flatow. Eight glasses of water per day, 2,000 calories of food per day, eight hours of sleep per night. There are many numbers that are supposedly the key to healthy living. And with the rise of wearable gadgets like Fitbits, activity trackers, and smartphones, our lives are more quantified than ever. But what benchmarks should we be using? Is there any scientific evidence behind these targets?

Amanda Paluch, an assistant professor of kinesiology at the University of Massachusetts, Amherst decided to dig further into one of the most popular health goal posts, the idea that you should walk at least 10,000 steps per day. She recently published her findings in the journal, JAMA Network Open and she joins us now. Amanda, Welcome to Science Friday.

AMANDA PALUCH: Thanks for having me.

UMAIR IRFAN: So before we get into your study, let’s talk about these 10,000 steps, where did this mythical number actually come from?

AMANDA PALUCH: So the back story is that in the mid-1960s, a Japanese pedometer was produced and it roughly translated to 10,000 steps meter. And this has really stuck in the mainstream media until now. And there really hasn’t been any scientific evidence to support this 10,000 step goal.

UMAIR IRFAN: I didn’t realize that number was so old. Does that mean that there is really no data to back it up at all?

AMANDA PALUCH: Yeah, there really hasn’t been. In order for these studies like how we’ve looked at in terms of your risk of death, you have to have a long follow-up. And also we have to have studies where participants actually wore these types of devices. So these types of studies did not start coming around until really the early 2000s was when we started to put devices on participants. And then giving it enough time to follow these participants to actually look at these health outcomes.

UMAIR IRFAN: Your study, however, did actually conduct a scientific assessment and look at real-world data. So what did you actually find when you actually looked at the results?

AMANDA PALUCH: So in our study, we broke groups into those who accumulated less than 7,000 steps, those who accumulated between 7,000 and 10,000 steps, and those who had greater than 10,000 steps. And really what we found is the individuals who took at least 7,000 steps per day had a 50% to 70% lower risk of premature death compared to those who took less than 7,000 steps per day. It was also interesting that we saw that the risk reductions tended to level off at 10,000 steps per day. So meaning that we didn’t see any additional benefit going beyond 10,000 steps.

UMAIR IRFAN: That’s interesting. So 10,000 actually sort of forms the plateau of where you start seeing these benefits. Does that mean though then I should adjust my Fitbit and set it at 7,000 from here on out?

AMANDA PALUCH: So if you’re already at 10,000, stick with 10,000. The great message about this study is that there’s benefits earlier than 10,000. So for those who are struggling to get to that level, who have really not been thinking about physical activity or feel like that 10,000 steps just is a little too much for what they can handle, just getting a little bit more can make a difference in your health. So it’s really not saying that 10,000 is worse than 7,000, it’s really saying that there is incremental benefits as you increase your activity levels. And then, once you get beyond that 10,000 you’re not going to get much more benefit but there’s not harm in doing more than 10,000, in terms of the results that we found for this cohort of middle-aged adults.

UMAIR IRFAN: So generally, it’s still good to get more exercise?

AMANDA PALUCH: Absolutely. It is 100% still good to get more exercise. So if you’re getting your 10,000 steps, that is awesome and you should continue to do that.

UMAIR IRFAN: The data that you used in this study, where did it come from? Did you track people who already had these Fitbits and how long were you tracking them?

AMANDA PALUCH: So this comes from a study called the CARDIA Cohort Study. And this study has been around since the mid-1980s. And how this study works, it’s funded by the National Institute of Health, and they followed a group of young adults starting in 1985. And they followed them for risk of cardiovascular disease. And about every five years, they do data collection on these participants.

And in 2005 they put an accelerometer, which is a research-grade device that measures activity. You could think of it similar to a pedometer, a Fitbit is also a type of accelerometer. So they put an accelerometer on these individuals and we have about 2,000 participants who have this data.

And then we have additional follow-ups where we were then able to follow them for death. And we have about 11 years of follow-up on these people. So we were able to see whether their steps per day was associated with their premature death risk.

UMAIR IRFAN: And this CARDIA study that you’re drawing on, this was focused on cardiovascular health but the benefits you saw were declines in all-cause mortality. How does that work?

AMANDA PALUCH: Absolutely. So for this study like you mentioned, we looked at death from any cause. It provides a nice metric to look at in terms of just your risk of premature death and indication of your health. We hope to further look at outcomes such as cardiovascular disease. And this study also has outcomes like diabetes, and hypertension, and obesity. And so these are our next steps in terms of what we hope to look at because this study only looks at all-cause mortality but there could be different associations depending on the outcome you’re looking at. So that’s why we hope to look at these additional outcomes as we pursue this research.

UMAIR IRFAN: And the people in this study, how representative are they? How much can we read into the results you saw in this group?

AMANDA PALUCH: So this study, in particular, provided a nice distribution of both Black and white adults, and also an equal distribution of men and women. And it comes from four different geographical locations within the United States. So it’s not a perfect representation but it does give a decent representation, particularly among Black and white, middle-aged men and women. Of course, it’s not going to extend beyond that to other race and ethnic groups.

UMAIR IRFAN: Does this then have implications for public health? Like should we be telling couch potatoes and people staying at home to start taking 7,000 steps in a day? Will we see immediate benefits if we start doing that?

AMANDA PALUCH: So yes, I think this is kind of the main public health message. Is that if you are not moving, getting to that 7,000 steps could be a really great goal, particularly for those who are inactive right now. So thinking about those incremental ways of increasing your activity.

And the great thing about steps per day in terms of a public health message is we can fit steps into our daily lives. And like we talked about, the wearable technologies, we have access to tracking our steps throughout our day. And this provides the opportunity to think about unique ways that we can fit in these steps in just our daily living.

So this provides this really nice public health message that you don’t need to go and get out and go run several miles if you don’t have the time to do that. Think about just parking further away from the store, or perhaps opting for the stairs instead of the elevator. Or opt for a walking meeting, or even taking a few laps around the soccer field while you’re waiting for your kids to finish up practice. So these are just some simple ideas that we can think about just getting in a few steps per day that could be very meaningful for our health.

UMAIR IRFAN: Now, I’m somebody who likes to walk really fast and I tell myself that’s an easy way to get exercise but your study found that the pace of walking really didn’t make much of a difference. How do you make sense of that?

AMANDA PALUCH: So yes, you’re right, in terms of our study did not find any clear associations with stepping intensity or pace. Now, this can be challenging to tease out because those who step faster also tend to get in more daily steps. We tried to account for this in our analyses, and our results did show that stepping intensity or pace was not associated with mortality beyond the total number of steps taken. So according to our results getting your steps regardless of the pace at which you walk them was associated with a lower death risk.

It’s worth noting that, again, this is just focused on premature death. And this could look different, the pace at which you’re walking could be meaningful for other health outcomes. And this should be continued to look at in other populations as well. So this is kind of some preliminary evidence that we’re not seeing very much in terms of the pace of what you’re walking. And just getting that total number of steps is more meaningful. But I think there’s still some more research to be done on this topic.

UMAIR IRFAN: Now, these activity trackers and these devices are getting more sophisticated all the time. My phone now claims to be able to measure my heart rate, my breathing, and my sleep habits. What metrics would you like to study next if you could actually measure them?

AMANDA PALUCH: So that’s a great question. And you’re absolutely right, that these wearables technologies are really growing and rapidly. And so the accelerometer that’s in these wearable devices that gets the steps per day is really just the start of being able to look at health and health behaviors.

We’re really interested in potentially pursuing these other metrics to see how it can maybe give us a better representation of people’s activity and fitness levels. A lot of these wearable devices and these additional metrics still need a lot of work and perfection, which is why steps per day is a nice, clean one. It’s been around for a while. So we have a lot more confidence in terms of the validity of those. But as wearable technologies continue to develop, we hope that we can combine these to better understand somebody’s health from a physical activity perspective.

UMAIR IRFAN: Do you have a specific question in mind that you’re looking to answer or a mystery you’d like to solve?

AMANDA PALUCH: One thing that we would be interested in and has been shown in the past, is in terms of looking at somebody’s fitness levels. So we have a physiological measure of someone’s fitness. And so when we think about fitness, that’s your ability to run faster for longer or to walk longer, those types of things. Your cardiovascular fitness, which has been tightly linked to your risk of all-cause mortality like we’re looking at here, as well as cardiovascular disease, and other health outcomes.

And as these wearable technologies grow and we get other metrics such as heart rate, and those become more perfected, combining physical activity with heart rate data, or for example, your electrodermal activity, which is your perspiration. Getting those types of metrics in combination, we might get an idea of somebody’s fitness level. And so we’re hoping that maybe in the future, this could be something we could look at and be a reliable measure.

Because right now we have to put somebody on a treadmill and do these very sophisticated measurements that are rather burdensome on a participant. So if we can get a level and estimate of fitness in a wearable technology and be able to look at that with health outcomes, I think that could be very informative and meaningful for future tracking. And then people could have the access to those type of fitness metrics.

UMAIR IRFAN: Well, I would be definitely interested in seeing what you come up with.

AMANDA PALUCH: Well, thanks.

UMAIR IRFAN: I’d like to thank my guest this hour, Amanda Paluch. She is an assistant professor of kinesiology at the University of Massachusetts, Amherst. Thanks for joining me today.

AMANDA PALUCH: Thank you so much for having me.

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