Associations between physical activity levels and echocardiographic parameters of cardiac fitness in the general population

Background Physical inactivity is a well-established risk factor for cardiovascular diseases. While its adverse effects have been documented in HF patients, the relationship between objectively measured physical activity (PA) and echocardiographic markers of cardiac health in asymptomatic, middle-aged individuals remains underexplored. This study investigates the association between accelerometer-measured PA and echocardiographic parameters linked to cardiac remodeling and HF risk in a healthy cohort. Methods Data from 4,955 participants in 2 cities subsets of the Swedish CArdioPulmonary bioImage Study (SCAPIS) were analyzed. Participants (aged 50–64 years, free of HF (asymptomatic and EF>50%), atrial fibrillation, or myocardial infarction) wore accelerometers for ≥4 days to measure PA levels, expressed as log-transformed counts per minute (CPM). Echocardiographic assessments included left ventricular mass index (LVMI), left atrial volume index (LAVI), septal e′ velocity, septal E/e′ ratio, stroke volume, left ventricular ejection fraction (LVEF), and interventricular septal thickness. Linear and logistic regression models assessed associations between PA and echocardiographic parameters across three models: Model 1 (unadjusted), Model 2 (adjusted for age and sex), and Model 3 (adjusted for age, sex, BMI, systolic blood pressure, diabetes, NT-proBNP, smoking, study site, and accelerometer wear time). Results Differences across physical activity quartiles showed that individuals with higher physical activity had lower BMI, lower blood pressure, lower prevalence of hypertension and diabetes, and that women tended to be more physically active. In fully adjusted models, CPM was positively associated with LVMI (β = 6.4, p = 0.001), LAVI (β = 3.5, p < 0.001), and stroke volume (β = 4.0, p < 0.001). Increasing CPM was linked to a lower E/e' ratio in models adjusted for age and sex (β = -0.9, p < 0.001), but the association weakened after adjustment in model 3 (β = -0.3, p = 0.069). Higher CMP was associated with lower odds of septal e' < 7 (Model 2: OR = 0.70, 95% CI: 0.50–0.98, p = 0.038) and E/e' > 14 (Model 2: OR = 0.51, 95% CI: 0.34–0.76, p = 0.001), though these associations were attenuated in fully adjusted models. Conversely, increasing CPM was associated with higher odds of LAVI > 34 ml/m² across all models (Model 3: OR = 2.15, 95% CI: 1.64–2.83, p = 0.001) and LVH (Model 3: OR = 1.74, 95% CI: 1.31–2.31, p = 0.001). Conclusions This study highlights significant associations between objectively measured PA and echocardiographic markers of cardiac remodeling. While PA is linked to beneficial cardiac changes, such as increased LVMI and stroke volume, it is also associated with larger LAVI. These findings emphasize the role of PA in cardiovascular health and suggest that atrial remodeling in active individuals warrants further investigation. Longitudinal studies are needed to explore causality and clinical implications.