Real-world tracking of exercise habits with a smartphone may inform future cardiovascular research.
Image: © Halfpoint/Thinkstock
Nearly two-thirds of Americans own a smartphone, which comes in handy for instant access to all sorts of information, from driving directions to medical advice. According to a Pew Research Center report, 62% of people have used their phone to research a health condition.
But smartphones can also collect personal health data, aided by apps that track your activity level throughout the day. Because activity and fitness levels are so closely tied to heart health, an accurate assessment of these factors may offer new clues for preventing heart disease.
A recent study involving nearly 50,000 volunteers from all 50 states who downloaded Apple’s MyHeart Counts app suggests that this type of research is feasible. “This study highlights how smartphones can be powerful tools for rapidly connecting researchers to the daily activities of a large number of people willing to participate in a study,” says Dr. Kevin King, a cardiologist at Harvard-affiliated Brigham and Women’s Hospital.
But whether smartphone-based research will be viable and useful beyond the demographic in this study—mostly healthy men in their 30s—will be interesting to see, says Dr. King. It will be important to find ways to engage a broader cross-section of the population, including people of different ages and socioeconomic groups and those with common, chronic diseases, he adds.
What counts for heart health?
The study, published January 1, 2017, in JAMA Cardiology, addresses a problem inherent in earlier studies: relying on people to estimate the time they spend exercising or doing other activities. People consistently overestimate their activity levels—a trend this study reaffirmed.
Researchers asked the participants to keep their phones with them as much as possible during a weeklong monitoring period, during which the tiny sensors inside the phone monitored their activity. Although only about 4,500 participants completed the entire seven days, more than 20,000 people completed two consecutive weekdays and two weekend days of monitoring.
The participants also provided basic health information, such as weight, blood pressure, and cholesterol levels, and filled out occasional surveys on topics such as diet, risk perception, work-related and leisure-time physical activity, sleep, and cardiovascular health status.
An advantage to intermittent activity?
As expected, more activity was linked to better self-reported cardiovascular health. But the pattern of activity also mattered. Among groups of people with similar activity levels, those who were active in short bursts throughout the day rather than a single, relatively short interval reported better cardiovascular health. They had lower rates of chest pain, heart attacks, and atrial fibrillation. These findings jibe with previous research showing that people who sit for long, uninterrupted periods are more likely to have diabetes, obesity, and other heart-related risk factors (though it’s not possible to say which condition came first). “Weekend warriors” who got most of their exercise on the weekends were among the healthiest participants.
More than 34,000 of the participants self-reported their sleep time, which averaged 7.8 hours per night. People who went to bed earliest in the evening had higher overall life satisfaction scores compared with those who stayed awake the latest.
Current challenges and future opportunities
In addition to the challenge of recruiting a more diverse population of participants, this study raises other limitations associated with smartphone-based research, says Dr. King. One obvious problem is that people don’t carry their phones at all times. What looks like sedentary time may actually just be a phone left on a table or in a purse. But motion-tracking sensors are common in wristband fitness trackers and increasingly in smartwatches, which could be used in addition to smartphones.
The type, duration, vigor, and regularity of physical activity very likely affects heart health, says Dr. King. “It will be interesting to see if future technologies can tease out these factors and help guide people to patterns of activity that provide the most cardiovascular benefit,” he says.
Perhaps the biggest challenge is keeping people engaged in doing physical activity—not just for a seven-day study but also for the rest of their lives. One potential solution is “gamification”—adding features to the app that give feed-back (both negative and positive) and rewards for greater activity and participation.