Kesson Magid

Platelets, coronary heart disease, and stress

Coronary heart disease is the leading cause of death in Western society, and its development is associated with chronic stress and other psychosocial factors. Atherosclerosis, the disorder underlying this disease, is an inflammatory process in which leukocytes interact with structurally intact but dysfunctional endothelium of the arteries. Platelets play a key role in this process by binding to leukocytes and promoting their recruitment to the endothelium. Platelet-leukocyte interactions also stimulate the release of pro-inflammatory and pro-thrombotic factors which promote atherosclerosis. Elevated circulating levels of platelet-leukocyte aggregates have been reported in cardiac patients and in individuals of low socioeconomic status, a factor associated with chronic psychological stress. Increased platelet activation has also been observed in individuals prone to depression or hostility, and in people subject to high levels of work stress. Acute psychological stress increases circulating platelet-leukocyte aggregates in healthy individuals and this effect is prolonged in cardiac patients. Platelet activation may be a mechanism linking psychosocial stress with increased coronary risk, and may also play a role in the emotional triggering of acute coronary syndromes in patients with advanced coronary disease.

The impact of time of waking and concurrent subjective stress on the cortisol response to awakening.

Both time of awakening and stress are thought to influence the magnitude of the cortisol awakening response (CAR), but the relative importance of these factors is unclear. This study assessed these influences in a combined within- and between-subject design. Data were collected from 32 men and women working as station staff in the London underground railway system in three conditions: early-shift days, day-shift days, and control days. Saliva samples were obtained on waking, 30 and 60 min later, together with measures of concurrent subjective stress, sleep quality the night before, and accumulated stress at the end of the day. Participants woke up more than 3.5h earlier on average on early-shift than day-shift or control days, and cortisol levels on waking were lower in the early-shift condition. The CAR (assessed both with increases from waking to 30 min and with area under the curve measures) was greater on early-shift days. However, respondents were more stressed over the hour after waking and reported more sleep disturbance on early-shift days; when these factors were taken into account, the difference in CAR related to experimental condition was no longer significant. Comparisons were also made between individuals who started their day-shifts in the morning and afternoon. The morning shift group woke an average of 2h earlier than did the afternoon shift group, but did not differ on stress, sleep quality, or CAR. Stress assessed retrospectively at the end of the day was not associated with the CAR. We conclude that early waking, stress early in the day, and sleep disturbance often coincide, but need to be distinguished in order accurately to interpret differences in CAR magnitude.

Exaggerated platelet and hemodynamic reactivity to mental stress in men with coronary artery disease.

Objective: This study compared the effects of acute mental stress on cardiovascular and subjective responses and platelet activation in male patients with established coronary artery disease (CAD) and age-matched controls. Methods: We assessed 17 male CAD patients aged 44 to 59 years and 22 healthy male controls. Blood pressure, heart rate, and hemodynamics were assessed before, during, and up to 2 hours after administration of color/word and mirror tracing tasks. Blood was sampled at baseline, after tasks, and at 30 and 75 minutes after stress, and platelet activation was assessed by measuring platelet-leukocyte aggregates (PLAs) using flow cytometry. Results: CAD patients showed significantly greater systolic blood pressure stress responses than controls (mean increases of 43.9 and 28.3 mm Hg, adjusted for income, body mass index, waist/hip ratio, and medication), together with larger increases in heart rate (14.1 and 4.7 bpm) and cardiac index. Total peripheral resistance increased during the poststress recovery period in CAD patients but not in controls. PLAs increased with stress in both groups, but remained elevated at 75 minutes in CAD patients, returning to baseline in controls. Heart rate and cardiac index responses were correlated with increases in subjective stress and with depression ratings, whereas PLA responses were associated with ratings of task difficulty. Conclusion: Acute mental stress stimulated heightened cardiovascular responses in CAD patients, coupled with more prolonged platelet activation. These factors may contribute to plaque rupture and thrombogenesis, and partly mediate stress-induced triggering of acute coronary syndromes.

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.

An evolutionary perspective on male preferences for female body shape

Cross-culturally, humans make systematic use of physical attractiveness to discriminate among members of the opposite sex, and physical cues to youth, health, and fertility may be particularly important to men (Buss, 1989). Nevertheless, there is controversy over whether attraction preferences are adaptive, particularly in novel environments, and whether they are universal or flexible depending on cultural circumstances (Singh & Luis, 1995). To date, a good deal of research into somatic (i.e., body) attractiveness has focused on two particular characteristics: waist-to-hip ratio (WHR) and the body mass index (BMI). WHR is calculated as the circumference of the waist divided by circumference of the hips, and provides an index of a woman’s ‘curvaceousness.’ BMI is calculated as an individual’s weight (kilogrammes) divided by height (metres) squared, and provides an estimate of body fatness.

On sex and suicide bombing: an evaluation of Kanazawa's 'evolutionary psychological imagination'

Kanazawa (2007) proposes the ‘evolutionary psychological imagination’ (p.7) as an authoritative framework for understanding complex social and public issues. As a case study of this approach, Kanazawa addresses acts of international terrorism, specifically suicide bombings committed by Muslim men. It is proposed that a comprehensive explanation of such acts can be gained from taking an evolutionary perspective armed with only three points of cultural knowledge: 1. Muslims are exceptionally polygynous, 2. Muslim men believe they will gain reproductive access to 72 virgins if they die as a martyr and 3. Muslim men have limited access to pornography, which might otherwise relieve the tension built up from intra-sexual competition. We agree with Kanazawa that evolutionary models of human behaviour can contribute to our understanding of even the most complex social issues. However, Kanazawa’s case study, of what he refers to as ‘World War III’, rests on a flawed theoretical argument, lacks empirical backing, and holds little in the way of explanatory power.

The complicated affairs of hormones and humans

“Living organisms are flexible;” begins the chapter by Pablo Nepomnaschy and Mark Flinn in Endocrinology of Social Relationships, “they can respond to changing conditions through a variety of morphological, physiological and behavioral mechanisms.” (p.365). Few mechanisms could be more flexible than the hormonal and social variety abundantly illustrated throughout this volume of contributions to reproductive endocrinology edited by Peter Ellison and Peter Gray. This is a book dedicated to two confoundingly flexible systems: social relationships, subject to a diversity of relational styles, and the distinctions of state versus trait, competitive versus protective, partnered versus unpartnered, etc., and the endocrine system, made up of exquisitely balanced axes, feedback or threshold effects and a multiplicity of target receptors. Endocrinology of Social Relationships attempts to integrate these two systems within the dicipline of behavioural endocrinology, crossing the fields of psychology, anthropology and biology. Along the way, one encounters a number of fascinating details, for instance marmosets and humans are the only two primates where males sympathetically gain weight during a mate’s pregnancy (p.144), and a brief affiliative interaction brings on a transspecies oxytocin release in both adult men and dogs (ODENDAAL and MEINTJES 2003), the same hormone that increases in both mother and infant during breastfeeding. Edited by two reproductive ecologists, the social relationships and the hormonal systems covered are almost exclusively related to reproduction within an evolutionary framework. The focus on reproduction means the sex steroids testosterone