Step Counts vs. Time-Based Exercise for Health

Comparison of Physical Activity Monitoring Methods and Health Outcomes in Women: A Study Summary.

A recent study published in JAMA Internal Medicine sought to compare two methods for monitoring physical activity (PA) levels—clocks and step counters—to determine which, if either, is more closely associated with better health outcomes in women in their 60s.

The study, which used a cohort study design, found that both monitoring methods showed similar relationships with cardiovascular disease (CVD) and all-cause mortality.

This suggests that health guidelines can be flexible in allowing individuals to choose their preferred metric.

Background

Maintaining physical health is essential for reducing the risk of premature death and non-communicable diseases.

According to the 2018 U.S. guidelines, adults should engage in at least 150 minutes of moderate or 75 minutes of vigorous aerobic PA each week, based on self-reported activity data.

However, these guidelines do not include step count goals due to a lack of evidence.

Recently, there has been growing interest in using daily steps as a health indicator, driven by the popularity of fitness trackers and smartphones.

Studies have shown an inverse relationship between step counts and all-cause mortality, particularly significant at 6,000-8,000 steps for older adults and 8,000-10,000 steps for younger individuals.

Higher step counts are also linked to better cardiovascular health. However, there has been no direct comparison between step-based and time-based PA metrics until now.

About the Study

This study aimed to fill this research gap by comparing the associations of these metrics with CVD and all-cause mortality.

The researchers hypothesized that both metrics would show similar associations, supporting the use of step counts as an alternative or complement to time-based PA recommendations.

Participants were drawn from the Women's Health Study, a long-term prospective cohort study initially designed to assess the effects of low-dose vitamin E and aspirin on preventing CVD and cancer among 39,876 women aged 45 or older.

Between 2011 and 2015, 62% of the surviving participants agreed to join a secondary study that measured PA using accelerometers.

After excluding participants who did not comply with the study requirements and those with a history of cancer or CVD, 14,399 women were included in the analysis.

Participants wore an accelerometer on their hips for seven consecutive days, excluding water and sleep activities.

The device collected data on moderate to vigorous PA (MVPA) and step counts. MVPA was defined as an accelerometer vector magnitude of 2690 counts or more per minute, and step counts were calculated using the device's step algorithm. Data were averaged over compliant days.

The study tracked participants until December 31, 2022, recording outcomes such as CVD events (fatal and nonfatal myocardial infarction, stroke, and other CVD mortality) and all-cause mortality.

Covariates like medical history, health habits, and sociodemographic characteristics were collected through annual questionnaires.

Statistical analyses categorized participants into quartiles based on step counts or MVPA time.

Cox proportional hazards regression models examined associations with mortality and CVD, accounting for factors such as smoking status, alcohol intake, diet, hormone therapy, self-rated health, and body mass index (BMI).

Sensitivity analyses and restricted mean survival time (RMST) calculations further validated the findings.

Findings

The study included 14,399 women with an average age of 71.8 years. The median MVPA time was 62 minutes per week, and the median step count was 5,183 steps per day.

A strong correlation was found between step counts and MVPA time (r = 0.82). Over a median follow-up period of nine years, 9.2% of participants died, and 4.1% developed CVD.

Higher levels of MVPA and step counts were associated with lower event rates: the lowest quartile had a 19.0% mortality rate, while the highest quartile had a 4.8% mortality rate. Similarly, step count-based mortality ranged from 19.3% to 4.0%.

Cox regression models indicated inverse associations between PA metrics and health outcomes.

For each standard deviation increase, the hazard ratios (HRs) for all-cause mortality were 0.82 for MVPA and 0.74 for step counts; for CVD, the HRs were 0.81 and 0.82, respectively.

Participants meeting PA guidelines had HRs of 0.68 for all-cause mortality, 0.57 for CVD (MVPA), and 0.58 and 0.72 for step counts.

RMST models showed that those in the top three quartiles of PA survived about 2.22 to 2.36 months longer. The area under the curve (AUC) for both metrics was similar (0.55). Sensitivity analyses confirmed these results.

Conclusions

The research found that both MVPA time and step counts are equally linked to lower all-cause mortality and cardiovascular disease (CVD) in women aged 62 and older.

Strengths of the study include its large sample size, the use of devices to measure physical activity, and thorough adjustments for potential confounding factors.

However, there are limitations, such as possible variations in physical activity over time, limited generalizability due to the specific demographic, and the potential for reverse causation.

Future studies should focus on more diverse populations and additional health outcomes to strengthen the case for incorporating step-based metrics into physical activity guidelines.

Source: medical

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