Higher daily step count reduces mortality in middle-aged adults

New findings using daily step count analysis show that regular physical activity in middle-aged adults reduces the chances of mortality associated with cardiovascular disease.

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Finding a relevant and effective metric for physical activity

Physical activity provides health benefits for many conditions such as cardiovascular disease, diabetes, and several cancers, and generally improves the quality of life of individuals. As such, regular exercise is one of the most important behaviors to improve or maintain individual health.  

To examine how physical activity affects various health conditions, researchers have used a variety of metrics to quantify daily activity, including the number of daily steps taken by people. However, studies have only recently considered using this metric with clinical endpoints, such as mortality, to determine the efficacy of the metric itself.

In a new study published in the JAMA Network by American researchers led by Dr. Amanda Paluch from the Institute for Applied Life Sciences at the Department of Kinesiology from the University of Massachusetts, scientists were able to establish a clear linkage between daily step count and mortality.

All-cause mortality was examined from a prospective cohort study part of the Coronary Artery Risk Development in Young Adults (CARDIA) study, with individuals aging between 38 and 50 years old. Data was collected from Black and White men and women between 2005 and 2006 with the help of an accelerometer.

This provided information on daily step volume, intensity, and time spent active. Participants were classified as having low step volume (<7000 steps/d), moderate (7000-9999 steps/d), and high (>10 000 steps/d) with peak 30-minute stepping rate counting as stepping intensity and time spent at 100 steps/min or more as active time.

A range of covariates were included to avoid the interference of confounding factors. This included characteristics of age, race, education, smoking history and alcohol consumption, BMI, and dietary habits. This information was self-declared by participants, who also declared their health status as either poor, fair, good, very good, or excellent.

50% to 70% lower risk of mortality for adults taking at least 7000 steps compared to those that take under 7000

Researchers analyzed the data using a series of regression models corrected for the various covariate factors. Each model included a subset of covariates to account for differences in step volume, intensity, and activity, with non-significant interactive effects being set aside gradually.

Importantly, a sensitivity analysis was also conducted to account for deaths during data collection, with 72 of the 2110 participants dying over the study period.

The analysis showed that, relative to the low step group, groups with moderate to high step rates had a reduced risk of mortality in Black and White participants as well as among both men and women.

Comparing covariate groups, researchers found Black and female participants took fewer steps than White and male participants respectively. However, step intensity was not associated with mortality as step volume was the significant metric involved.

The associations of step count with mortality but not step intensity aligned with previous findings that used the same accelerometer on another cohort of over 6000 participants, as well as studies from Norway that considered step count as a proxy for physical activity.

The lack of ethnic and socioeconomic diversity among studies of this type remains to be resolved, as data remains lacking on the high-risk group. This is of particular concern as the lowest step group had the highest rates of cardiovascular disease, hypertension, and diabetes, and were associated with minority groups.

The study had several strengths including long-term follow-up data collection. Nonetheless, it remains an observational study. Moreover, the range of covariates and confounding factors may induce indirect effects difficult to incorporate into the analysis, as health conditions often overlap with physical activity.

Future studies based on these findings could include a further breakdown of the differential factors affecting step volume, and determine why step intensity may not be as important. Including further diversity into cohorts is also key as insight is lacking on high-risk groups that may not have the support needed.

Written by

James Ducker

James completed his bachelor in Science studying Zoology at the University of Manchester, with his undergraduate work culminating in the study of the physiological impacts of ocean warming and hypoxia on catsharks. He then pursued a Masters in Research (MRes) in Marine Biology at the University of Plymouth focusing on the urbanization of coastlines and its consequences for biodiversity.