Yes, You Should Aim for 10,000+ Steps
The latest in misleading health media.
Posted Jul 10, 2019
As consumers in the 21st century, we enjoy unparalleled access to information to guide our decisions about health. Paradoxically, we also struggle with the opposite reality: We live in an era of unparalleled misinformation capable of confusing and misdirecting even well-intentioned readers.
Perhaps most frustrating of all is that one of the latest examples of health misinformation to go viral originated from a respected observational study of women (called the “Women’s Health Study”) and was published in May by one of the most prestigious medical journals (JAMA Internal Medicine). The authors of this study described relationships between the average number of daily steps among women wearing an accelerometer (a high-quality activity tracker often used in research) for 4-7 days and their risk of dying over a 4.3-year follow-up period.
Based on the step counts observed, the authors grouped the women into quartiles. The least active women averaged about 2,700 or fewer steps a day, whereas the most active women averaged nearly 8,500 steps a day. The main finding was that more steps per day predicted a lower risk of death for women during the follow-up period—up to about 7,500 steps a day—above which more activity added no further statistical benefit.
Had the health media translated these results accurately for consumers, their message might have read: “More physical activity predicts a lower risk of premature death among older-aged women, but with diminishing returns for the most active women.” Factual research reporting is rarely sexy, however. Instead, many media outlets sensationalized the results with the message: “You don’t need to walk 10,000 steps a day!” This is a misleading and potentially harmful interpretation of the Women’s Health Study findings. Let’s look at four reasons why:
1. Most people aren’t walking to prevent short-term death.
Survey research indicates that nearly 1 in 3 adults in the U.S. use an activity tracker. However, among these 50+ million users, few of them are tracking their steps to prevent their demise in the next 4.3 years. Even if the study results are true, since most people are tracking their steps to achieve goals other than death prevention, the results have limited applicability to them. To generalize a relationship between steps per day and short-term death risk to all the other reasons why people are trying to increase their activity levels is deceptive and way beyond the actual results of the study.
So why are many people tracking their steps these days? Research suggests it is for reasons such as losing weight, improving fitness and function, managing health conditions, and feeling better physically and emotionally. Exercise research is also clear that more and higher-quality physical activity is superior for all these goals. For example, data from the National Weight Loss Registry—made up of participants who have lost and maintained at least 30 pounds of weight for a year or more—suggests a need for 60-90 minutes of exercise per day. This translates into 11-12,000 steps a day, even higher than the commonly cited 10,000-step goal.
2. You probably aren’t a 72-year-old woman.
One of the major improvements in health research in the 21st century is the increased focus on women and ethnic minority groups. The Women’s Health Study is a great example of this scientific progress. However, it is also true that this study's focus on the narrow demographic of older-aged women greatly limits the conclusions we can draw about other age groups. For example, the relationship between exercise and short-term death risk is negligible for younger people, because their overall risk of dying is much lower over a 4-5-year period, even though exercise is beneficial for this part of the population in many other ways. With only about 13 percent of the U.S. population aged 65 or older according to 2010 Census data (and nearly half of those being men), the main finding of the study doesn’t apply to 87 percent of Americans. And, again, even for this important 13 percent, the results only apply to short-term death risk rather than to other health or quality of life benefits of exercise.
3. Short samples of physical activity are often inaccurate.
If you study the methods of the paper published in JAMA Internal Medicine, you may notice that the researchers based their exercise-death relationship on just 4-7 days of women wearing the accelerometer. This is standard practice in observational studies because it is difficult to closely monitor people’s behaviors for long periods of time. However, health research also shows that these brief samples of behavior can be inaccurate for many reasons. Some people, for example, are more active when they know they are being monitored and resume their normal habits afterward. Other times, the sampling period may not be representative of a person’s normal life (due to travel, illness, or other atypical life events during the period), or people’s activity levels simply change over time. How well could we estimate the next 4.3 years of your exercise and health habits based on what we measured from you this week?
4. The benefits of walking on death risk are too small to matter for many people.
Lost in the “statistical significance” of the findings is an interpretation of what the results mean for a typical person hoping to lower their health risks with exercise. Because the results were observational rather than randomized, it is a mistake to infer that steps per day directly caused or prevented deaths in this study. This is the classic “correlation does not equal causation” error. Even were we to assume a causal relationship for discussion purposes, however, it is also important to determine how large or meaningful the relationship is for people like those in the study (older-aged women). In this case, we know that 504 of 16,741 women died over the follow-up period in the study, translating into an average death risk of 3 percent. Further, the authors shared that every 1,000 steps per day were associated with a 15 percent reduction in death risk. Because 15 percent of 3 percent is 0.45 percent, this means that an average 72-year-old woman in the study might lower her risk of death in the next 4.3 years from 3.0 percent to 2.55 percent by increasing her steps by 1,000 per day. A healthier woman, whose death risk was just 1 percent over the same period would reap an even smaller benefit from more activity (i.e., from 1 percent to 0.85 percent). Is this amount of risk reduction likely to motivate many older-aged women to become more active?
Don't throw away your Fitbit or pedometer. Despite the many headlines from this study questioning the validity of the 10,000 steps-a-day recommendation, there is substantial research demonstrating the benefits of this or even greater levels of regular physical activity.
Lee I, Shiroma EJ, Kamada M, Bassett DR, Matthews CE, Buring JE. Association of Step Volume and Intensity With All-Cause Mortality in Older Women. JAMA Intern Med. Published online May 29, 2019. doi:10.1001/jamainternmed.2019.0899