How many steps a day are required for middle-aged adults to reduce coronary artery risk development (CARD)?

Introduction

The role of regular physical activity has been proven vital to reduce several health risks such as cardiovascular disease, diabetes, and several cancers, as well as to improve overall quality of life. Walking is the most common functional activity which can be measured objectively by counting steps. It can be a calculated prescription physical activity to enhance health and reduce all-cause mortality. Most studies in the past have largely focused on geriatric population comparing mortality by step volume and intensity. 

Purpose of this research

A need for research in populations with diverse individual characteristics, including age, race, and gender was identified by the Physical Activity Guidelines Advisory Committee. Also, there are limited number of studies demonstrating the prospective associations of step volume and intensity with clinical outcomes, including mortality. Therefore, the National guidelines for physical activity does not include step counts as a public health target. 

This prospective study was conducted in middle-aged Black and White adults in response to the need for empirical data on the associations of step volume and intensity with mortality in younger and diverse populations. The objectives of this research were: 

1. To study correlation of step volume and intensity (in diverse population) with mortality and 
2. Follow up for mortality for approximately 11 years

Methods and sampling

5155 adults aged 18 to 30 years were included at baseline in 1985 to 1986. Sampling was balanced by race, gender, age and education from 4 US locations (Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California).

In-person examination of all participants was performed at baseline and following years with respective retention rate:

• 91% at year 2
• 86% at year 5
• 81% at year 7
• 79% at year 10
• 74% at year 15
• 72% at year 20
• 72% at year 25
• 71% at year 30

ActiGraph 7164 accelerometer was worn on the hip by participants for 7 consecutive days during all waking hours. Participants with wear time of 10 h/d for at least 3 days were included. Patients were categorized in to 3 groups:

• low (<7000 steps/day)
• moderate (7000 to <10000 steps/day)
• high (≥ 10000 steps/day) 

Outcomes

Primary outcome was all-cause mortality assessed by contacting participants or designated proxies twice per year to check vital status. Searches of the National Death Index were conducted every 5 years and participants were followed up for death through August 31, 2018. 

Other covariates like age, race, gender, smoking & alcohol history, height, weight, dietary history, medical history, fasting glucose, cholesterol and mean blood pressures were also recorded during their visits. 

Results and inferences

2110 participants with mean (SD) age 45.2 (3.6) years were included in final analysis after excluding drop-outs, non-adherence and missing data. Mean (SD) time from baseline to end of follow-up was 10.8 (0.9) years. During 22 845 person-years of follow-up, 72 of 2110 participants (3.4%) died with 1) cancer (18 participants) and 2) cardiovascular disease (17 participants). Researchers have noted key findings such as:

• Nearly half of the participants took over 9000 steps/day.
• It was also observed that unlike those in moderate and high step group, participants in the low step group had higher BMI, lower self-rated health, and higher prevalence of stage 2 hypertension and diabetes.
• The high step group was dominated by white participants and males. 
• Significantly reduced mortality risk was associated in high stepping black participants in race analysis. 
• High step rates were associated with reduced risk for women compared to the low stepping counterparts in gender analysis. 

In the low step/day group there were significantly greater proportion of women (280 women [62.5%]) and Black participants (241 participants [53.8%]).

Overall, the researchers found significantly lower risk of all-cause mortality for participants in moderate (hazard ratio 0.28 and 95% CI) and high (hazard ration 0.45 and 95% CI) step groups. 

Study limitations

As per the researchers, observational design of the study limits conclusions regarding the causal pathway of the association of steps with mortality. 

Residual confounding and reverse casualty potential possibility remain for participants health status at the time of study. 

If the participants dropped out or passed away or did not adhere to wearing the accelerometer at 20-year follow-up, selection biased may have resulted. Also, accelerometer data may not have adequately captured bouts less than 1 minute which are common in daily life. 

Free-living stepping intensity were not exactly represented as they were developed in controlled settings of treadmill walking at constant speeds. 

ActiGraph 7164 device specific step count values provided in this study may not be precisely applicable to every wearable activity monitor as it can estimate 15% to 25% more steps compared with other common devices. 

Conclusion 

The researchers hence conclude that “taking at least 7000 steps/d during middle adulthood was associated with a lower risk of mortality”, specially in the least active population. They did not find an association between step intensity with mortality.

Source 

This article was published on JAMA open network on September 3, 2021. 

Link

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2783711

Author

Amanda E. Paluch, PhD, Institute for Applied Life Sciences, Department of Kinesiology, University of Massachusetts.