The influence of psychological stress and socioeconomic status on platelet activation in men.

OBJECTIVE: Circulating monocyte- and neutrophil-platelet aggregates are sensitive markers of in vivo platelet activation. Socioeconomic status is inversely associated with risk of coronary heart disease. We assessed the impact of psychological stress on leukocyte-platelet aggregates in men from higher and lower socioeconomic status groups. METHODS: Participants were 37 healthy non-smoking men aged 30-59 years, divided by occupation into higher and lower social status groups. Blood was drawn at baseline, immediately following stressful behavioural tasks, and at 30 and 75 min post-stress, and aggregates were analysed using flow cytometry. Cardiovascular and subjective stress responses were also monitored. RESULTS: There were significant increases following stress in monocyte-, neutrophil-, lymphocyte- and total leukocyte-platelet aggregates (all P<0.05). The largest responses were in monocyte-platelet (21% increase) and neutrophil-platelet (16.7% increase) aggregates. Lower socioeconomic status men had greater numbers of leukocyte-platelet aggregates throughout, but the magnitude of stress responses did not vary with social status. The increase in monocyte- and leukocyte-platelet aggregates was associated with systolic blood pressure stress responsivity. CONCLUSIONS: Psychological stress induces platelet activation as indexed by leukocyte-platelet aggregates, and correlations with cardiovascular stress reactions suggest that sympathoadrenal responses may be responsible. Platelet activation may be a mechanism through which social position influences cardiovascular disease risk.