BACKGROUND: Heterogeneous myocardial contraction is common in myocardial disease and linked to ventricular arrhythmias, but its frequency and relevance in the general population remain unclear. This study aimed to investigate the frequency of increased left ventricular mechanical dispersion (LVMD) and to examine its clinical and imaging correlates in a population-based cohort. METHODS: LVMD was assessed using speckle-tracking echocardiography in 3997 participants aged 50-64 years (51% women) from the Swedish Cardiopulmonary Bioimage Study. The upper limit of normal (ULN) for LVMD was defined as the 95th percentile in a subgroup (n=1165) without cardiovascular disease or risk factors. In the full cohort, cardiovascular risk factors, including coronary artery calcium score (CACS) and left ventricular mass index (LVMI) from cardiac CT, were compared between subjects with and without high LVMD, and predictors of high LVMD were assessed using multivariable regression. RESULTS: The ULN for LVMD was 53 ms and LVMD>ULN was present in 11.8% of the full cohort. These individuals were older, more often male, had higher body mass index (BMI) and more frequently had hypertension, hyperlipidaemia and previous myocardial infarction. They also had higher LVMI (57±11 g vs 52±11 g, p<0.001). CACS ≥100 was present in 17.8% vs 10.3% (OR 1.90, 95% CI 1.46 to 2.48, p<0.001) in those with increased versus normal LVMD. Age, BMI, LVMI and heart rate were independently associated with LVMD. CONCLUSIONS: LVMD above ULN was observed in 11.8% of this middle-aged general population sample and was associated with a more adverse cardiovascular risk profile and markers of cardiac remodelling, particularly higher LVMI and larger indexed left ventricular volumes.