Research Background and Question

In modern society, the patterns of physical activity (PA) and their impact on health have been a critical area of public health and medical research. Traditional studies have primarily focused on the total volume and intensity of physical activity. However, in recent years, an increasing number of studies have begun to explore physical activity fragmentation. Physical activity fragmentation refers to frequent transitions from active to sedentary states, which may affect overall health status. Although existing studies have shown that physical activity fragmentation is associated with all-cause mortality in older adults and non-Hispanic whites, these studies are mostly limited to specific age groups and ethnicities, with short follow-up periods.

Therefore, further exploration is needed regarding the impact of physical activity fragmentation on different populations, especially Hispanic/Latino adults. This study aims to evaluate the association between physical activity fragmentation and all-cause mortality in Hispanic/Latino adults and investigate whether this association is independent of total physical activity volume. Through this study, the authors hope to provide new insights into how physical activity patterns influence health and offer scientific evidence for developing health interventions targeting Hispanic/Latino populations.

Paper Source

This paper was co-authored by Mauro F. F. Mediano, Yejin Mok, Shoshana H. Ballew, and several other researchers from various institutions, including the Evandro Chagas National Institute of Infectious Diseases at the Oswaldo Cruz Foundation in Brazil and the Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health in the USA. The study was published in The Lancet Regional Health - Americas, with the journal reference 2025;42: 100996, and the DOI link is https://doi.org/10.1016/j.lana.2025.100996. The title of the paper is “The Association of Physical Activity Fragmentation with All-Cause Mortality in Hispanics: A Prospective Cohort Study.”

Research Process

Study Population and Data Collection

This study is based on data from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), a community-based prospective cohort study conducted in four U.S. cities: Bronx, New York; Chicago, Illinois; Miami, Florida; and San Diego, California. The study population included Hispanic/Latino adults aged 18 to 74 years, with a total of 16,415 participants recruited. Among them, 14,913 participants provided accelerometer data. After screening, the final sample size for analysis was 11,992 participants.

Data Processing and Analysis Methods

Accelerometer Measurement and Calculation of Physical Activity Fragmentation Indicators

The study used Actical accelerometers (Respironics Co. Inc.), requiring participants to wear them continuously for seven days to record daily physical activity. The accelerometer collected data every minute, which was used to calculate the daily average activity count (Total Log-Transformed Activity Counts, TLAC). To assess the degree of physical activity fragmentation, the study introduced Active-to-Sedentary Transition Probability (ASTP), defined as the probability of transitioning from an active state to a sedentary state per minute. ASTP was calculated as 1 divided by the average active bout duration (minutes). Additionally, TLAC-adjusted ASTP was calculated to exclude the influence of total physical activity volume.

Monitoring of Death Events

Death events were identified through annual follow-up interviews, obituary searches, or matches to the National Death Index. Follow-up time was from enrollment until January 31, 2022, during which 745 deaths occurred.

Statistical Analysis

Complex sampling design and weighted regression models were used to analyze the data, ensuring the results were representative. Specifically, the study first stratified adjustments based on demographic characteristics, clinical variables, and lifestyle factors, then used Cox regression models to evaluate the relationship between ASTP and all-cause mortality. To verify the linear relationship between ASTP and mortality, restricted cubic spline models were constructed. Additionally, sensitivity analyses were conducted, including only participants with ≥5 valid accelerometer days and excluding deaths within the first two years to reduce potential confounding factors.

Research Results

Baseline Characteristics

Overall, individuals with higher ASTP often had poorer lifestyle and health statuses, such as higher BMI, more comorbidities, more depressive symptoms, lower diet quality, lower levels of physical activity, and higher sedentary time. These individuals were more likely to be Dominicans, Cubans, and Puerto Ricans, with relatively higher education levels and insurance coverage.

Survival Analysis Results

During an average follow-up period of 11.2 years, 745 deaths occurred, with a 10-year cumulative mortality rate of 4.8 per 1,000 person-years. The results showed that compared to the lowest tertile, the highest tertile of ASTP had a hazard ratio (HR) of 1.45 (95% CI 1.10–1.92) for all-cause mortality. For each 0.1-unit increase in ASTP, the risk of mortality increased by 22% (HR 1.22; 95% CI 1.07–1.39). Even after adjusting for total physical activity volume, this association remained significant, with the highest tertile of TLAC-adjusted ASTP having an HR of 1.46 (95% CI 1.06–2.00) compared to the lowest tertile.

Sensitivity Analysis

Sensitivity analyses indicated that the association between ASTP and mortality remained significant both in sub-samples with ≥5 valid accelerometer days and when excluding deaths within the first two years. Subgroup analyses also showed consistent associations between ASTP and mortality among men and women, as well as those <60 years and ≥60 years old.

Conclusion and Significance

This study systematically evaluated the relationship between physical activity fragmentation and all-cause mortality in Hispanic/Latino adults for the first time, finding that higher ASTP is associated with a higher risk of mortality, independent of total physical activity volume. The results support ASTP as an emerging marker of physical activity patterns, aiding in identifying poor prognosis risks and providing scientific evidence for developing interventions to improve daily physical activity patterns. For example, increasing continuous activity time (e.g., sustained walking) can reduce physical activity fragmentation, thereby lowering mortality risk. Future research should further explore the relationship between ASTP and other health outcomes and develop effective intervention strategies to optimize daily physical activity patterns.

Research Highlights

1. Key Findings: First confirmed the significant association between physical activity fragmentation and all-cause mortality in Hispanic/Latino adults, independent of total physical activity volume.
2. Significance of the Issue: Addressed the lack of diversity and short follow-up periods in existing studies, filling a research gap in Hispanic/Latino populations.
3. Novelty of Method: Introduced ASTP as an indicator of physical activity fragmentation, providing a more comprehensive reflection of daily physical activity patterns, including light and moderate-to-vigorous activities.
4. Application Value: Provided new perspectives for public health policymakers, emphasizing the importance of improving daily physical activity patterns, especially for Hispanic/Latino populations.

Other Valuable Information

Despite using rigorous statistical methods and data analysis techniques, some limitations exist. For instance, the lack of cause-of-death information limits detailed analysis of cause-specific mortality; hip-worn accelerometers may not accurately capture certain types of activities (e.g., cycling or swimming); and some information relied on self-reports, potentially introducing information bias. However, these limitations do not affect the main conclusions and instead highlight directions for future research.