Association of daily step counts and step intensity with mortality among US adults: a cross–sectional study of NHANES 2005–2006

Metabolic dysfunction–associated steatotic liver disease (MASLD), characterized by hepatic steatosis along with at least one cardiometabolic risk factor (CMRF) and no other known cause, is estimated to affect approximately 30% of adult worldwide [1, 2]. MASLD is not only a liver–related condition but also a multi–system disease associated with cardiovascular disease (CVD) and extrahepatic cancers [3, 4]. Previous studies have shown that MASLD is associated with an increased risk of all–cause mortality [5].Currently, no pharmacological treatments are approved specifically for MASLD, making lifestyle interventions, including physical activity, the primary approach for managing the disease [5, 6].

Among physical activities, walking is one of the most accessible and popular options for the general population [7]. Over the past decade, the use of consumer–grade wearable activity monitors has increased substantially. These devices provide real–time feedback on both step counts and step intensity, allowing individuals to track their physical activity more effectively. Several studies leveraging this technology have shown that step–based recommendations are key to reducing mortality risk, with evidence drawn from diverse populations, including US adults [8], older women [9] and young adults [10]. However, to date, research focused on individuals with MASLD remains limited. Given the high prevalence of MASLD, the prevalence of MASLD underscores the urgency of developing specialized, evidence–based guidelines for this population [11]. Despite the importance of physical activity, no public health guidelines currently specify the optimal number of steps MASLD patients should take daily to reduce their mortality risk. Moreover, walking can be performed at different intensity levels, adding complexity to assessing its effects on health outcomes [9, 12, 13]. However, the relationship between step intensity and mortality remains unclear.

The National Health and Nutrition Examination Survey (NHANES) (www.cdc.gov/nchs/nhanes) is designed to assess the health and nutritional status of adults and children in the United States [8]. The survey is distinctive in that it incorporates both physical examinations and interviews. Several cross–sectional, nationally representative health examination surveys are part of the NHANES program. Questions about demographics, health insurance status, dietary habits, acute and chronic medical issues, mental health, and prescription drug use are all included in the health interview. Exam components can change between survey cycles but typically include blood pressure, dental exams, vision, hearing, dermatology, fitness, balance and strength testing, respiratory testing, taste and smell, and body measurements (weight, height, skin folds, body composition scans). Hematology, organ and endocrine function (e.g., thyroid, kidney), environmental exposure, dietary biomarkers, metabolic and cardiovascular health, and infectious disease are some laboratory components. In this study, we present data from NHANES to examine the associations of daily step counts and step intensity with mortality in individuals with MASLD. Additionally, our secondary objective was to explore whether step intensity is independently associated with mortality.

In the study, a total of 1,108 subjects were enrolled, and their initial baseline characteristics are presented (Table 1). The mean age at baseline was 49.5 years, with a standard deviation of 0.9 years. Of these individuals, 533 (48.1%) were women and 575 (51.9%) were men. Racially, 809 (73%) were non-Hispanic whites, 122 (10.8%) were non-Hispanic blacks, 133 (12.0%) were Hispanic, and 44 (4.2%) were from other racial backgrounds. The median follow–up duration for participants was 13.8 years. Participants with MASLD who engaged in higher levels of physical activity, as measured by step counts, were younger, had lower BMI and smaller waist circumferences, and were more likely to be cohabiting and identified as moderate drinkers. They also had a lower prevalence of cardiometabolic risk factors, such as hypertension and impaired glucose metabolism, and were less likely to rate their general health as fair or poor.

To our knowledge, this is the first study to link daily step counts and intensity to all-cause mortality in individuals with MASLD. Several key findings emerged from our results. First, even minimal levels of stepping activity (i.e., just above the 10th percentile of the exposure distribution, 3,800 steps per day for participants with MASLD) is associated with a roughly 30% reduction in all-cause mortality risk compared to those with 500 steps per day. Second, increasing daily steps is linked to a consistent decrease in mortality risk up to around 10,000 steps, beyond which the risk plateaus. Finally, we found no significant association between step intensity and all-cause mortality in the MASLD population.

While previous research has established the beneficial effects of increased step count on mortality in general and older populations, our study highlights the unique relevance of this relationship in MASLD [8, 23]. Several studies have explored the relationships between daily step counts and health outcomes, including cardiovascular disease, dementia, and all–cause mortality. For example, Cruz et al. [24] found that up to 10,000 steps per day may be linked to a decreased incidence of cardiovascular disease. Similarly, another study suggested that a number of steps fewer than 10,000 per day may be optimally associated with a lower risk of dementia [25]. However, a meta-analysis suggests that 8,000 steps per day may be the ideal threshold for reducing all-cause mortality risk, beyond which no further risk reduction is observed [26]. In this study, we found J-shaped nonlinear associations between daily step count and all-cause mortality. Notably, once the step count exceeds 10,000, the reduction in mortality risk seems to plateau, suggesting that higher step counts may not offer additional benefits for individuals with MASLD. Recent studies suggest that higher levels of exercise may increase the risks of adverse health outcomes. For example, DeFina et al. [27] demonstrated that strenuous joggers appeared to have higher mortality. Similarly, two studies [28, 29] found that higher levels of physical activity, such as marathon running, are linked to increased coronary artery calcification. These findings align with ours, emphasizing the need for step-count guidelines tailored to MASLD patients.

Studies of self-reported walking speed have found that higher walking speeds are associated with lower mortality risk [13]. However, the present study provides limited evidence that step intensity is associated with lower mortality, similar to findings from a study among older women [9]. One possible explanation for this inconsistency is that self-reported walking speed is subjective, while our study used an objective monitor to measure walking speed. After adjusting for age and gender confounders, peak 1 cadences showed that the highest intensity was not linked to reduced mortality, mainly due to individuals with lower step intensity being older. After adjusting for all included confounders factors, step intensity was no longer associated with mortality. Several factors may account for this finding. Firstly, adjustment for BMI and age is essential, as both are significant predictors of both physical activity levels and mortality in individuals with metabolic diseases [30, 31]. Particularly, age is a well–established factor influencing both the likelihood of engaging in physical activity and overall health outcomes. Older age is frequently associated with a decline in physical function, comorbid conditions, and increased mortality risk [32]. When adjusted for age and BMI, the independent effect of walking intensity on mortality may be attenuated, suggesting that the influence of physical activity on mortality could be mediated by these age–related factors. Additionally, including self-reported health status in our models may have further reduced the impact of walking intensity. Self–reported health serves as a proxy for various unmeasured factors, such as underlying comorbidities, physical function, and psychological health, all of which can influence both physical activity participation and mortality risk [33]. These factors may have confounded the relationship between walking intensity and survival, obscuring any potential direct effect of walking intensity on mortality. The cadences estimates (steps/min) used here should be interpreted with caution, as they reflect the steps accumulated per minute of accelerometer observation, not the steps taken during a full minute of walking [34]. Therefore, further studies using more accurate measures of walking speed are needed to confirm these findings.

This study has important practical implications for public health interventions targeting individuals with MASLD. Our findings suggest that achieving higher daily step counts, rather than focusing solely on step intensity, can significantly reduce the risk of all–cause mortality in this population. Given the simplicity and feasibility of increasing daily physical activity, healthcare providers may consider incorporating step count monitoring into routine care for MASLD patients to track progress and encourage sustained physical activity. By setting clear, measurable step goals, clinicians can improve patient compliance and potentially reduce long-term health risks associated with MASLD.

Future research should explore the combined effects of daily step counts and intensity on mortality in MASLD patients. Longitudinal studies using modern accelerometers could help clarify these associations, particularly in diverse MASLD populations with varying disease severities. Additionally, incorporating other lifestyle factors, such as diet and comorbid conditions, could provide a more comprehensive understanding of the impact of physical activity on mortality. Subgroup analyses based on disease stages (e.g., simple steatosis vs. steatohepatitis) could offer valuable insights into how physical activity interventions can be better tailored to enhance outcomes in MASLD patients.

Our study has several strengths. First, it was conducted using the NHANES database, which offers a population-based design and a large sample size, thus enhancing the robustness of our findings. Second, with a mean follow-up of 13.8 years, this study benefits from one of the longest durations exploring the association between step counts and mortality in MASLD patients.

However, the present study also has several limitations. First, the data presented are observational, precluding causal claims, even though we reanalyzed the data after excluding participants who experienced the event within the first two years of follow–up. Second, missing data and residual confounding may still affect the results. Third, the association between low step counts and mortality should be interpreted with caution due to the lack of data at low levels of exposure. Fourth, while data from a 7-day monitor are informative, they may not capture longer-term variations in step counts. Fifth, self-reported measures, although common in large-scale epidemiological studies, are prone to biases such as recall and social desirability bias. Sixth, cultural differences in reporting disease status and physical activity may influence results. Additionally, age-period-cohort (APC) effects may be present but were not assessed. The use of accelerometer data from 2005–2006, based on older technology, is another limitation. Finally, MASLD diagnosis relied on the FLI rather than liver biopsy.

Our findings suggest that achieving 10,000 steps per day may be optimal to lower the risk of all-cause mortality among individuals with MASLD.