Good for you: less exercise than you might think

Just a few months ago we shared with you a meta-analysis of research into levels of physical activity and its impact on the risk of death from any cause (known as "all-cause mortality"). The authors found that after breaking down levels of activity into four, from least active to most active, those who were in the second-to-lowest level of activity were still 52% less likely to die of any cause than those who were least active (in the lowest level of activity).

Conversely, compared to those who were most active, those who were most sedentary were over 260% more likely (that's more than twice as likely) to die of any cause.

You might think that this means that you need to take up a 10-mile-a-day running habit or something equally strenuous. Nothing could be further from the truth.

In an article published just this month in JAMA (2020;323(12):1151-1160), researchers from such institutions as the National Cancer Institute, the Centers for Disease Control and Prevention (CDC), and the National Institute on Aging analyzed data gathered through NHANES (National Health and Nutrition Examination Survey), a long-term, large-scale study of adults across the United States that began recruitment in 2003.

A portion of the participants in NHANES wore accelerometers for an average of almost 6 days (about 14.5 hours per day) in 2003-2004. These 4,840 participants averaged almost 58 years of age at that time (minimum age for participation: 40).

At the end of 2015 the authors accessed the National Death Index to find out which of those accelerometer-wearing participants had passed away and their cause of death, then correlated that information with not only average step count but also step intensity (that is, walking speed).

After taking into account sex, age, diet quality (evaluated through a food frequency questionnaire), Body Mass Index at the start of the study, and the presence of chronic diseases such as diabetes, high blood pressure, or heart disease, the authors found that compared to those who accelerometers registered less than 4,000 steps per day, those who achieved 8,000 steps per day were 51% less likely to die of any cause. Those who achieved 12,000 steps per day were 65% less likely to die of any cause.

The authors looked specifically at the risk of death from cardiovascular disease as well as cancer, finding that the decrease in risk, although present, did not reach statistical significance.

When they analyzed step intensity (that is, Were those who walked faster at reduced risk?), the authors found no significant association between intensity and mortality - when they took into account the overall number of steps.

The authors caution that those who wore the accelerometers in this study tended to have a Body Mass Index over 30 (clinically obese) and were less likely to be those with a diagnosis of heart disease or heart failure or to have mobility problems. Further, those whose step count was higher were more likely to have a lower rate of diabetes, heart disease, or cancer, and tended to report themselves as being in good health.

What this means for you

While it's clear that those with a higher step count tended to be healthier, generally speaking, than those with a lower step count, this does suggest that a moderate amount of regular exercise is beneficial to almost everyone. 10,000 steps? Great, but not necessary. The risk differential between 8,000 and 12,000 steps isn't that significant.

The authors also noted that the accelerometers the participants wore do not differentiate between walking for exercise and performing household chores or gardening, nor do they include exercise such as swimming or cycling.

We encourage you to get a total of at least thirty minutes of activity every day while (right now) being mindful of social distancing measures. This exercise doesn't have to be outside!

First posted: April 1, 2020