Step count matters - lowers risk of death

By Dr. Liji Thomas, MDMar 24 2020

A new study shows that wearing a device that measures the number of steps taken over the course of the day reduces the overall death rate in US adults. The study was published in the journal JAMA in March 2020.

Many health and fitness organizations promote the goal of 10,000 steps a day, but there is not much evidence that this is a beneficial outcome or that it actually lowers the rate of early death in adults. Existing research does indicate that death rates fall in proportion to higher step counts, but this has been carried out among older ad sicker populations, or conversely in groups at relatively low risk of death. The intensity of stepping was also not clearly associated with better health outcomes.

Greater numbers of steps per day were associated with lower risk of all-cause mortality. Image Credit: Kaspars Grinvalds / Shutterstock

The study

The current study was motivated by the need to know if the step count and step intensity affected the death rate in US adults aged 40 or more. The researchers used data from the National Health and Nutrition Examination Survey (NHANES) protocols from 4,840 adults.

The participants wore an ActiGraph model accelerometer throughout their waking hours for seven days. All those who wore it for at least one day of 10 or more hours were included in the study. Other variables included race, demographic factors, chronic health conditions and habits, height and weight, and diet quality. The perception of the individual as to overall health and the mobility of the participant was also examined among the over-60 group or the people who are under 60 but have physical or mental issues.

The parameters

The accelerometer used was 99% accurate in measuring the number of steps (step count) and the step intensity, or cadence. Cadence was measured as the mean bout cadence, the peak 30-minute cadence, and the peak 1-minute cadence. Peak 30 cadence was calculated as the overall mean of the daily mean of the 30 highest cadence values collected each day. Peak 1 cadence was calculated by selecting the highest minute cadence value each day and getting the mean over all days.

The findings

The individuals wearing the accelerometers had a higher level of education than usual, had a higher BMI or drank, and many had chronic medical conditions like heart disease and limitations on mobility.

A higher step count was observed among individuals who were younger, leaner, ate poorer food, educated, and drank. However, the occurrence of chronic conditions like diabetes and heart disease among this group was lower.

The mean number of steps was over 9,000 a day. Over the ten years of follow up, on average, there were 1165 deaths, with over 400 deaths due to cardiovascular disease, and over 280 resulting from cancer.

Step counts were associated with lower mortality from all causes as well as fewer deaths from cancer and from cardiovascular disease. In those who took 2,000 steps a day, the mortality was 50% higher than those who took 4,000 steps a day. In those who took 8,000 steps vs. 4000 steps, the difference in the all-cause death rate was halved. With 12,000 steps a day, the mortality was reduced by almost two-thirds compared to those who took 4,000 steps a day.

In short, the higher the step count, such as in 8,000 steps vs. 4,000 steps, the lower was the mortality, with the former group having half the death rate of the latter, in men and women alike. In older and younger adults, the mortality dipped by 60% and 40%, respectively.

When compared with the mortality, the step cadence showed an inverse relationship. The death rate was about 33/1000 person-years for 18 – 56 steps per minute. At 56 to 69 it is about 12.6. It goes on falling until it reaches a low of 5.3 in the group who took 82 to 150 steps per day. However, when adjusted for the total number of steps taken, the peak 30 and peak 1 cadence measures were not significantly linked to mortality.

Implications

The study suggests that the use of wearable activity monitors could help lower the death rate among users by providing instant data about the number of steps taken, which tends to help improve physical activity in the right setting. Moreover, the study findings should be used to set appropriate goals for fitness in terms of step count, taking into consideration the baseline fitness, health limitations, and the number of steps taken at the beginning of the program. Such devices are accurate and could be useful in increasing the life span among US adults by helping to increase the step count.