INTRODUCTION

Inflammatory biomarkers have received increasing attention because of their associations with cardiovascular disease and cancer. Along with smoking cessation, moderate alcohol consumption, and a healthy diet, physical activity is recognized as a key determinant of health. However, approximately 31% of adults worldwide do not meet recommended physical activity levels [1], and physical inactivity remains a major contributor to disability and premature mortality worldwide.

Recent World Health Organization guidelines on physical activity and sedentary behavior emphasize limiting sedentary time, and the revised Korean Physical Activity Guidelines similarly highlight the importance of minimizing daily sitting time in conjunction with physical activity [2,3]. Despite this growing emphasis, most public health programs and policies continue to focus primarily on increasing physical activity, with comparatively less attention given to reducing sedentary behavior.

Accumulating evidence indicates that prolonged sedentary time and insufficient physical activity are associated with increased risks of all-cause mortality as well as cardiovascular disease-related and cancer-related outcomes [4–6]. More recent epidemiological evidence further suggests that even modest reductions in sedentary time may yield meaningful population-level health benefits [7].

Notably, a joint report by the National Heart, Lung, and Blood Institute and the National Institute on Aging of the United States National Institutes of Health identified the potential adverse effects of increased sedentary time on cardiovascular outcomes among older adults [8]. Older adults often face functional limitations, fatigue, reduced motivation, and environmental constraints; thus, maintaining recommended levels of physical activity may be challenging [9]. These barriers underscore the need for feasible alternative behavioral strategies tailored to older populations.

C-reactive protein is an acute-phase protein produced in response to systemic inflammation and is widely used as a biomarker of inflammatory status. High-sensitivity C-reactive protein (hs-CRP) permits more precise measurement at lower concentrations, enabling discrimination within the normal range [10]. The Centers for Disease Control and Prevention and the American Heart Association have identified hs-CRP as a clinically useful marker for predicting cardiovascular disease risk, and related research has expanded accordingly [11].

Although a Korean study has examined sedentary behavior in relation to cardiovascular disease risk, evidence regarding inflammatory biomarkers in nationally representative samples of older adults remains limited [12].

Therefore, this study examined whether prolonged sedentary time was associated with elevated hs-CRP levels among Korean adults aged 65 years or older, using nationally representative data from the Korea National Health and Nutrition Examination Survey (KNHANES).

METHODS

Study Population

This study analyzed data from the 9th KNHANES (2022). Of 1667 participants aged 65 years or older with available hs-CRP measurements, 496 with leukocyte counts ≥10 000 cells/mm³ or hs-CRP levels ≥10.0 mg/L were excluded to minimize the influence of acute inflammatory conditions. Previous clinical and epidemiological studies have suggested that hs-CRP levels ≥10.0 mg/L are more likely to reflect acute infection or inflammatory conditions than chronic low-grade inflammation associated with cardiometabolic risk [11,13,14]. The final analytic sample included 1171 participants.

Independent Variable

The independent variable was sedentary time, assessed using self-reported KNHANES questionnaire data. Sedentary time was defined as the average daily time spent sitting or lying down, excluding sleep, during work, at home, while traveling, or during social activities. Examples included sitting at a desk, sitting with friends, traveling by car, bus, or train, reading, writing, playing cards, watching television, playing games (e.g., Nintendo, computer, or PlayStation), using the internet, and listening to music. Sedentary time was categorized using a threshold of 10 hr/day, based on previous epidemiological studies reporting increased mortality risk among individuals who sit for more than 10 hr/day [15].

Dependent Variable

The dependent variable was serum hs-CRP. Based on clinical classification criteria established by the Centers for Disease Control and Prevention and the American Heart Association, hs-CRP levels ≥1.0 mg/L were classified as abnormal [10]. This threshold represents a clinically meaningful level of systemic inflammation and has been associated with increased cardiovascular disease risk in previous research [13].

Covariates

Smoking status was categorized as current, former, or never smoker. Alcohol consumption was classified as drinking (yes) or non-drinking (no). Physical activity and regular walking practice were treated as binary variables. Clinical covariates included systolic blood pressure (≥140 or <140 mmHg), diastolic blood pressure (≥90 or <90 mmHg), fasting blood glucose (≥126 or <126 mg/dL), triglycerides (≥200 or <200 mg/dL), high-density lipoprotein cholesterol (<40 or ≥40 mg/dL), waist circumference (using a threshold of ≥90 cm for men and ≥85 cm for women), and body mass index (BMI; ≥25.0 or <25.0 kg/m²), based on established clinical criteria for cardiometabolic risk factors [14]. To avoid potential multicollinearity, waist circumference and BMI were not included simultaneously in the multivariable logistic regression models; waist circumference was selected as the adiposity indicator.

Statistical Analysis

Statistical analyses were performed using MedCalc version 23.4.8 (MedCalc Software Ltd, Ostend, Belgium). Differences in the prevalence of abnormal hs-CRP according to participant characteristics were assessed using the chi-square test, and prevalence ratios (PRs) with 95% confidence intervals (CIs) were calculated in the bivariate analyses. Multivariable logistic regression analysis was performed to evaluate the association between sedentary time and abnormal hs-CRP after adjustment for covariates; the results are expressed as odds ratios (ORs) and 95% CIs. Missing data were handled using complete-case analysis. Participants with missing values for the dependent variable or any covariate included in the multivariable logistic regression model were excluded from that analysis. Of the 1171 eligible participants, 79 were excluded because of missing data, resulting in 1092 participants being included in the multivariable logistic regression analysis. All p-values were two-sided, and a p-value <0.05 was considered statistically significant.

Ethics Statement

This study was a secondary analysis of publicly available, de-identified data from the KNHANES, administered by the Korea Disease Control and Prevention Agency. The researchers had no access to personally identifiable information and had no direct interaction with the survey participants. Separate institutional review board approval was not obtained for the present secondary analysis, and no additional informed consent was obtained from participants.

RESULTS

Socio-demographic Characteristics and High-sensitivity C-reactive Protein Levels

The prevalence of abnormal hs-CRP (≥1.0 mg/L) differed significantly across several socio-demographic characteristics. Men had a higher prevalence of abnormal hs-CRP than women (37.5 vs. 31.4%, p=0.030). Participants in lower household income quartiles had a significantly higher prevalence of abnormal hs-CRP than those in higher income groups (p=0.013). Educational attainment was also significantly associated with hs-CRP status; participants who had completed elementary school or less had the highest prevalence of abnormal hs-CRP (36.7%, p=0.002). Marital status was not significantly associated with hs-CRP levels (Table 1).

Health Behaviors, Laboratory Findings, and High-sensitivity C-reactive Protein Levels

Regular walking was significantly associated with abnormal hs-CRP. Participants who did not engage in regular walking had a higher prevalence of abnormal hs-CRP than those who did (37.0 vs. 29.9%, p=0.012), corresponding to a 24% higher prevalence (PR, 1.24; 95% CI, 1.05 to 1.46). No significant associations were observed for smoking status, alcohol consumption, or overall physical activity. Abnormal hs-CRP was also significantly associated with several cardiometabolic risk factors. Participants with systolic blood pressure ≥140 mmHg had a higher prevalence of abnormal hs-CRP than those with systolic blood pressure <140 mmHg (40.5 vs. 32.5%; PR, 1.25; 95% CI, 1.04 to 1.49). Elevated diastolic blood pressure (≥90 mmHg) was similarly associated with abnormal hs-CRP (PR, 1.43; 95% CI, 1.05 to 1.94). In addition, triglyceride levels ≥200 mg/dL (PR, 1.46; 95% CI, 1.20 to 1.77) and low high-density lipoprotein cholesterol levels (<40 mg/dL) were significantly associated with abnormal hs-CRP. Glycated hemoglobin levels ≥6.5% showed a borderline association with abnormal hs-CRP (Table 2).

Body Measurements and High-sensitivity C-reactive Protein Levels

Anthropometric measures were significantly associated with hs-CRP status. Participants with abdominal obesity had a higher prevalence of abnormal hs-CRP than those without abdominal obesity (39.6 vs. 28.8%; PR, 1.37; 95% CI, 1.17 to 1.62). Similarly, participants with BMI ≥25.0 kg/m² had a higher prevalence of abnormal hs-CRP than those with BMI <25.0 kg/m² (39.5 vs. 30.8%; PR, 1.28; 95% CI, 1.09 to 1.51). Mean BMI was also significantly higher among participants with abnormal hs-CRP levels (Table 3).

Sedentary Time and High-sensitivity C-reactive Protein Levels

In addition to anthropometric measures, prolonged sedentary time was significantly associated with abnormal hs-CRP. Participants with an average sedentary time of ≥10 hr/day had a higher prevalence of abnormal hs-CRP than those with <10 hr/day of sedentary time (PR, 1.20; 95% CI, 1.02 to 1.41; Table 4).

In multivariable logistic regression analysis, prolonged sedentary time remained significantly associated with abnormal hs-CRP after adjustment for smoking status, alcohol consumption, regular walking, systolic blood pressure, and waist circumference (OR, 1.31; 95% CI, 1.01 to 1.71; Table 5).

DISCUSSION

The present study found that prolonged sedentary time was independently associated with elevated hs-CRP levels among Korean adults aged 65 years or older. This association remained significant after adjustment for physical activity-related behaviors and major cardiometabolic risk factors, suggesting that sedentary time may be associated with systemic inflammation in older populations independently of these measured factors. These findings are consistent with previous studies reporting associations between sedentary behavior and elevated inflammatory biomarkers.

Previous epidemiological studies have consistently reported that prolonged sedentary behavior is associated with unfavorable cardiometabolic profiles and elevated inflammatory biomarkers. For example, analyses of nationally representative United States data showed that greater sedentary time was significantly associated with adverse cardiometabolic biomarkers, independent of physical activity levels [5,16]. Similarly, sedentary behavior has been associated with increased inflammation, dyslipidemia, impaired glucose metabolism, and insulin resistance, even among individuals who meet recommended levels of physical activity [6,17]. Recent large-scale epidemiological analyses further suggest that reducing sedentary time may contribute to meaningful improvements in population health outcomes [7]. The present findings support this concept by showing that sedentary time was associated with elevated hs-CRP after adjustment for walking practice and other cardiometabolic risk factors.

Experimental evidence provides further support for plausible biological mechanisms underlying these associations. Studies have shown that prolonged uninterrupted sitting may impair vascular endothelial function, whereas interrupting sedentary time with brief bouts of physical activity may improve endothelial responses [18,19]. In addition, replacing sedentary time with even light-intensity physical activity has been associated with improved survival and reduced mortality risk in population-based studies [20].

Recent epidemiological studies using objective measurement techniques have provided additional support for the association of sedentary behavior with cardiovascular risk and related health outcomes [21]. In Korea, trajectory-based analyses have highlighted the distinct roles of physical activity and sedentary behavior in cardiovascular risk profiles [12]. The present study extends these findings by demonstrating an independent association between sedentary time and systemic inflammation, as measured by hs-CRP, among older adults.

Sedentary behavior has become an increasingly important cardiovascular risk factor in aging populations [15]. Older adults often face barriers to maintaining adequate physical activity, including functional limitations, fatigue, reduced motivation, and environmental constraints.

Emerging evidence also suggests that prolonged sedentary behavior may be associated with neurodegenerative changes and cognitive decline in older adults [22]. Furthermore, previous studies have indicated that the adverse effects of sedentary behavior may persist even among individuals who meet recommended levels of physical activity [4].

Taken together, these findings suggest that reducing sedentary time may be a feasible complementary behavioral target for older adults who have difficulty achieving recommended levels of structured physical activity.

Therefore, intervention strategies aimed at reducing sedentary behavior should be developed alongside, but conceptually distinct from, strategies that promote physical activity. Such interventions should account for population characteristics, including age and functional capacity, as well as intervention settings, including individual, workplace, and community contexts. Previous expert consensus has emphasized the importance of context-specific and population-tailored approaches to reducing sedentary behavior [8], underscoring the need for targeted strategies rather than a one-size-fits-all approach.

By excluding participants with markedly elevated hs-CRP levels (≥10.0 mg/L) or leukocyte counts indicative of acute inflammation, this study focused on chronic low-grade inflammatory processes that are more relevant to long-term cardiometabolic risk. This approach improves the interpretability of hs-CRP as a marker of chronic systemic inflammation rather than acute infection [11,13,14].

Several limitations should be acknowledged. The cross-sectional design limits the ability to establish causal relationships between sedentary behavior and elevated hs-CRP. Furthermore, although the multivariable models adjusted for several behavioral and cardiometabolic variables, residual confounding due to unmeasured or incompletely measured socio-demographic factors cannot be excluded. Reverse causation also cannot be ruled out, because individuals with underlying health conditions may be more likely to spend prolonged periods in sedentary behaviors. In addition, sedentary time was assessed using self-reported questionnaire data, which may be subject to recall bias.

KNHANES does not provide detailed domains of sedentary behavior, such as television viewing versus occupational sitting, or allow assessment of potential non-linear associations, such as J-shaped associations. Future studies using domain-specific measures and flexible modeling approaches are warranted. Another limitation is that KNHANES data do not allow differentiation between continuous and interrupted sedentary patterns, although previous experimental studies suggest that these patterns may have distinct physiological effects [18,19]. Finally, hs-CRP was used as a surrogate biomarker rather than a direct clinical outcome.

Despite these limitations, this study provides nationally representative evidence on the association between sedentary behavior and inflammatory biomarkers among Korean older adults using 2022 KNHANES data. Generating local evidence is particularly important because cardiometabolic risk profiles and lifestyle patterns may differ across populations. Recent studies have also emphasized that multiple lifestyle behaviors, including sleep, physical activity, and sedentary time, collectively influence healthy aging and longevity outcomes [23]. For example, Korean older adults often have lower BMI but greater abdominal obesity than Western populations. Furthermore, the use of the 2022 KNHANES dataset reflects lifestyle patterns observed after the coronavirus disease 2019 (COVID-19) pandemic, providing timely insights for public health policy and healthy aging strategies in Korea. Future studies should further explore the potential interaction between sedentary behavior and physical activity by examining combined behavioral patterns, such as mutually exclusive categories of physical activity and sedentary time.

Future research should also examine sedentary behavior across different age groups, as recent public health discussions have highlighted a shift in unhealthy lifestyle patterns toward younger generations.

Overall, the findings of this nationally representative study suggest that prolonged sedentary behavior is a potentially modifiable contributor to systemic inflammation among older adults and underscore the importance of integrating sedentary behavior reduction into healthy aging strategies.

Implications and Recommendations

The findings of this study suggest that reducing sedentary behavior may be an important strategy for the prevention and management of chronic diseases. In chronic disease management, greater attention should be given to reducing sedentary time alongside traditional physical activity promotion. Sedentary time should be considered a modifiable behavioral risk factor that warrants active monitoring and intervention in public health strategies. Although most intervention evidence comes from working-age populations, trials aimed at reducing sitting time have demonstrated measurable cardiometabolic improvements [24].

Practical examples include encouraging regular movement breaks during prolonged sitting, introducing intentional break times in workplaces, and promoting sit–stand desk use to reduce prolonged sitting during work hours. Community-based programs that encourage light-intensity activities among older adults may also be beneficial. Such strategies may complement conventional physical activity promotion efforts and provide more accessible options for populations with limited capacity for structured exercise.

In Korea, community-based programs implemented through senior welfare centers and public health centers may provide practical platforms for reducing sedentary behavior among older adults. Incorporating scheduled movement breaks, light-intensity group activities, and environmental modifications within these settings may help reduce prolonged sitting time. Such initiatives could complement national health promotion strategies and contribute to healthy aging policies targeting Korea’s rapidly growing older population.

Continued monitoring and analysis of the relationship between sedentary time and hs-CRP are warranted. Establishing sustainable evidence generation platforms, such as the National Health Insurance Service database or the Community Health Survey, would facilitate ongoing surveillance and monitoring. These efforts could support the development of evidence-based policies and intervention strategies aimed at reducing sedentary behavior and preventing chronic diseases in aging populations.

Notes

Conflict of Interest

The authors have no conflicts of interest associated with the material presented in this paper.

Funding

None.

Acknowledgements

None.

Author Contributions

Conceptualization: Seol R. Data curation: Seol R, Cho SO. Formal analysis: Seol R, Cho SO. Funding acquisition: None. Methodology: Seol R, Cho SO. Project administration: Seol R. Visualization: Seol R, Chun C, Cho SO. Writing – original draft: Seol R, Chun C. Writing – review & editing: Seol R, Chun C, Cho SO.

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Figure & Data

References

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