Background: Unfavourable psychogenic factors increase the risk of cardiovascular outcomes. Aim of this study was to evaluate the impact of a positive psychological intervention (laughter) on aortic stiffness and wave reflections, known determinants of cardiovascular performance and predictors of the corresponding risk. Moreover, we sought to explore possible underlying mechanisms, notably inflammation, platelet activation, endothelial function and oxidative stress.

Methods: 18 healthy volunteers (age 28 ± 5 years) watched a 30 minutes long segment of a comic film. Measurements were made before, 0, 15 and 30 minutes after the movie. Carotid-femoral pulse wave velocity (cfPWV) was measured as an index of aortic stiffness. Wave reflections were studied using arterial tonometry; augmentation index (AIx) was measured as index of wave reflections. Blood samples were drawn before and 15 minutes after the movie. P selectin levels, soluble vascular cell adhesion molecule 1 (s VCAM-1), total antioxidant status (TAS) were measured by enzyme-linked immunosorbent assay.

Results: Laughter induced by the comedy led to a significant decrease in cfPWV by 0.30 m/sec and AIx by 3.83% (both at 15 minutes, p< 0.05). P selectin levels decreased by 18 ng/mL, sVCAM-1 decreased by 47.56 ng/mL, (all p<0.05). TAS did not change significantly, p=0.47.

Conclusions: This study shows that laughter has a beneficial effect on arterial elastic properties and wave reflections. Attenuation of endothelial injury, platelet activation and inflammatory response, as indicated by decreased levels of P selectin and sVCAM-1, is a possible underlying pathway, while oxidative status is not altered.