Background Cardiovascular disease (CVD) is the leading cause of death among older adults, with sedentary behavior (SB) as a key modifiable risk factor. While physical activity (PA) is associated with cardiovascular health, evidence remains limited on the specific effects of replacing SB with PA of varying intensities. Objective To systematically review evidence on the cardiovascular effects of substituting SB with PA in adults aged 65 and older using isotemporal substitution modeling (ISM). Methods Following PRISMA guidelines, seven databases were searched up to April 2025. Risk of bias was assessed using the JBI tool, and a narrative synthesis was conducted. Results Eighteen observational studies (15 cross-sectional, 3 cohorts) using ISM were included. Replacing 10–60 min of SB with moderate-to-vigorous PA (MVPA) was associated with more favorable in blood pressure, triglycerides, waist circumference, inflammatory markers (CRP, IL−6, GDF−15), and insulin sensitivity (HOMA-IS, Matsuda-ISI). Light-intensity PA (LPA) showed modest associations, particularly among frail or mobility-limited individuals. A daily substitution of 30 min was identified as a feasible reference window, with ≥60 min linked to additional vascular and autonomic benefits. Conclusions Replacing SB with PA, especially MVPA, was consistently associated with favorable cardiovascular profiles in older adults. Even brief substitutionsmay be beneficial, supporting intensity-stratified public health strategies and refinement of physical activity guidelines for aging populations.Because most included studies were cross-sectional, these findings should be interpreted as associations rather than definitive causal effects, and reverse causation remains a plausible concern. Systematic Review Registration https://www.crd.york.ac.uk/prospero/view/CRD420251021829/1/0 , PROSPERO CRD420251021829.
Sun et al. (Tue,) studied this question.