walking
To Prevent a Stroke, Household Chores and Leisurely Strolls May Help
Posted on by Lawrence Tabak, D.D.S., Ph.D.
As we get older, unfortunately our chances of having a stroke rise. While there’s obviously no way to turn back the clock on our age, fortunately there are ways to lower our risk of a stroke and that includes staying physically active. Take walks, ride a bike, play a favorite sport. According to our current exercise guidelines for American adults, the goal is to get in at least two and a half hours each week of moderate-intensity physical activity as well as two days of muscle-strengthening activity [1].
But a new study, published in the journal JAMA Network Open, shows that reducing the chances of a stroke as we get older doesn’t necessarily require heavy aerobic exercise or a sweat suit [2]. For those who are less mobile or less interested in getting out to exercise, the researchers discovered that just spending time doing light-intensity physical activity—such as tending to household chores—“significantly” protects against stroke.
The study also found you don’t have to dedicate whole afternoons to tidying up around the house to protect your health. It helps to just get up out of your chair for five or 10 minutes at a time throughout the day to straighten up a room, sweep the floor, fold the laundry, step outside to water the garden, or just take a leisurely stroll.
That may sound simple, but consider that the average American adult now spends on average six and a half hours per day just sitting [3]. That comes to nearly two days per week on average, much to the detriment of our health and wellbeing. Indeed, the study found that middle-aged and older people who were sedentary for 13 hours or more hours per day had a 44 percent increased risk of stroke.
These latest findings come from Steven Hooker, San Diego State University, CA, and his colleagues on the NIH-supported Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. Launched in 2003, REGARDS continues to follow over time more than 30,000 Black and white participants aged 45 and older.
Hooker and colleagues wanted to know more about the amount and intensity of exercise required to prevent a stroke. Interestingly, the existing data were relatively weak, in part because prior studies looking at the associations between physical activity and stroke risk relied on self-reported data, which don’t allow for precise measures. What’s more, the relationship between time spent sitting and stroke risk also remained unknown.
To get answers, Hooker and team focused on 7,607 adults enrolled in the REGARDS study. Rather than relying on self-reported physical activity data, team members asked participants to wear a hip-mounted accelerometer—a device that records how fast people move—during waking hours for seven days between May 2009 and January 2013.
The average age of participants was 63. Men and women were represented about equally in the study, while about 70 percent of participants were white and 30 percent were Black.
Over the more than seven years of the study, 286 participants suffered a stroke. The researchers then analyzed all the accelerometer data, including the amount and intensity of their physical activity over the course of a normal week. They then related those data to their risk of having a stroke over the course of the study.
The researchers found, as anticipated, that adults who spent the most time doing moderate-to-vigorous intensity physical activity were less likely to have a stroke than those who spent the least time physically active. But those who spent the most time sitting also were at greater stroke risk, whether they got their weekly exercise in or not.
Those who regularly sat still for longer periods—17 minutes or more at a time—had a 54 percent increase in stroke risk compared to those who more often sat still for less than eight minutes. After adjusting for the time participants spent sitting, those who more often had shorter periods of moderate-to-vigorous activity—less than 10 minutes at a time—still had significantly lower stroke risk. But, once the amount of time spent sitting was taken into account, longer periods of more vigorous activity didn’t make a difference.
While high blood pressure, diabetes, and myriad other factors also contribute to a person’s cumulative risk of stroke, the highlighted paper does bring some good actionable news. For each hour spent doing light-intensity physical activity instead of sitting, a person can reduce his or her stroke risk.
The bad news, of course, is that each extra hour spent sitting per day comes with an increased risk for stroke. This bad news shouldn’t be taken lightly. In the U.S., almost 800,000 people have a stroke each year. That’s one person every 40 seconds with, on average, one death every four minutes. Globally, stroke is the second most common cause of death and third most common cause of disability in people, killing more than 6.5 million each year.
If you’re already meeting the current exercise guidelines for adults, keep up the good work. If not, this paper shows you can still do something to lower your stroke risk. Make a habit throughout the day of getting up out of your chair for a mere five or 10 minutes to straighten up a room, sweep the floor, fold the laundry, step outside to water the garden, or take a leisurely stroll. It could make a big difference to your health as you age.
References:
[1] How much physical activity do adults need? Centers for Disease Control and Prevention. June 2, 2022.
[2] Association of accelerometer-measured sedentary time and physical activity with risk of stroke among US adults. Hooker SP, Diaz KM, Blair SN, Colabianchi N, Hutto B, McDonnell MN, Vena JE, Howard VJ. JAMA Netw Open. 2022 Jun 1;5(6):e2215385.
[3] Trends in sedentary behavior among the US population, 2001-2016. Yang L, Cao C, Kantor ED, Nguyen LH, Zheng X, Park Y, Giovannucci EL, Matthews CE, Colditz GA, Cao Y. JAMA. 2019 Apr 23;321(16):1587-1597.
Links:
Stroke (National Institute of Neurological Disorders and Stroke/NIH)
REGARDS Study (University of Alabama at Birmingham)
NIH Support: National Institute of Neurological Disorders and Stroke; National Institute on Aging
Why Flies and Humans Freeze When Startled
Posted on by Dr. Francis Collins
When faced with something unexpected and potentially ominous, like a sudden, loud noise or a threat of danger, humans often freeze before we act. This is colloquially referred to as the “deer in the headlights” phenomenon. The movie of fruit flies that you see above may help explain the ancient origins of the “startle response” and other biomechanical aspects of motion.
In this video, which shows a footrace between two flies (Drosophila melanogaster), there are no winners or losers. Their dash across the screen provides a world-class view of the biomechanics of walking in these tiny, 3 millimeter-long insects that just won’t sit still.
The fly at the top zips along at about 25 millimeters per second, the normal walking speed for Drosophila. As a six-legged hexapod, the fly walks with a “tripod gait,” alternating between its stance phase—right fore (RF), left middle (LM), and right hind (RH) —and its swing phase sequence of left fore (LF), right middle (RM), and left hind (LH).
The slowpoke at the bottom of the video clocks in at a mere 15 millimeters per second. This fly’s more-tentative gait isn’t due to an injury or a natural lack of speed. What is causing the delay is the rapid release of the chemical messenger serotonin into its nervous system, which models a startle response.
You may have already heard about serotonin because of its role in regulating mood and appetite in humans. Now, a team led by Richard S. Mann and Clare Howard, Columbia University’s Zuckerman Institute, New York, has discovered that fruit flies naturally release serotonin to turn on neural circuits that downshift and steady the speed of their gait.
As detailed recently in Current Biology [1], serotonin is active under myriad conditions to tell flies to slow things down. For example, serotonin helps flies weather the stress of extreme temperatures, conserve energy during bouts of hunger, and even walk upside down on the ceiling.
But the research team, which was supported by the NIH-led Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative, found that serotonin’s most-powerful effect came during an actual startle response, prompted by a sudden, jolting vibration. Scientists suspect the release of serotonin activates motor neurons much like an emergency brake, stiffening and locking up the fly’s leg joints. When the researchers blocked the fly’s release of serotonin, it interrupted their normal startle response.
In years past, such a detailed, high-resolution “action video” of Drosophila, one of the most-popular model organisms in biology, would have been impossible to produce. Fruit flies are tiny and possess extremely high energy.
But a few years ago, the Mann lab developed the approach used in this video to bring the hurried gait of fruit flies into tight focus [2]. Their system combines an optical touch sensor and high-speed video imaging that records the footfalls of all six of a fly’s feet.
Then, using the lab’s unique software program called FlyWalker , the researchers can extract various biomechanical parameters of walking in time and space. These include step length, footprint alignment, and, as the letters in the video show, the natural sequence of a tripod gait.
Drosophila may be a very distant relative of humans. But these ubiquitous insects that sometimes buzz around our fruit bowls contain many fundamental clues into human biology, whether the area of research is genetics, nutrition, biomechanics, or even the underlying biology of the startle response.
Reference:
[1] Serotonergic Modulation of Walking in Drosophila. Howard CE, Chen CL, Tabachnik T, Hormigo R, Ramdya P, Mann RS. Curr Biol. 2019 Nov 22.
[2] Quantification of gait parameters in freely walking wild type and sensory deprived Drosophila melanogaster. Mendes CS, Bartos I, Akay T, Márka S, Mann RS. Elife. 2013 Jan 8;2:e00231.
Links:
Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)
Mann Lab (Columbia University’s Zuckerman Institute, New York)
MouseWalker Colored Feet (YouTube)
NIH Support: National Institute for Neurological Disorders and Stroke; National Institute of General Medical Sciences
