Psychological stressors are related to different diseases, especially the heart disease and stroke.Platelet activation is potentially particularly important in the triggering process of thrombus formation and then contributes to an acute coronary syndrome.Platelet indices measured by hematology analyzers, such as mean platelet volume (MPV), platelet distribution width (PDW), and platelet large cell ratio (P-LCR), have been used to giving the fact of platelet activation caused by morphologic changes of platelets.We investigated different platelet responses following acute psychological stress among middle-aged and elderly cohorts, female and male groups.The aim was to determine whether an acute laboratory psychological stress task produced platelet reactivity by using three haematologicaly markers: MPV, PDW and P-LCR in healthy participants and whether there is age or gender related differences.Fifty-four healthy volunteers performed a psychological stress challenge.Blood samples were obtained pre-stress and immediately post-stress prior to haematologyical analysis.The participants were divided into middle-aged and elderly cohorts, or male and female groups.The acute psychological stressor induced a significant (P < 0.05) increase of MPV, PDW and P-LCR in healthy participants.There were no significant (P < 0.05) differences between middle aged and elderly cohorts, or male and female groups in our investigation.We conclude that as marks of platelet activation, the three indices measured by hematology analyzers: MPV, PDW and P-LCR are sensitively increased after acute lab psychological stress in healthyadults,and in both middle aged and elderly cohorts.