Effects of chronic social separation on cardiovascular disease risk factors in female cynomolgus monkeys

Social status predicts physiological and behavioral responses to chronic stress in rhesus monkeys

Investigating the underlying factors that cause differential individual responses to chronic stress is crucial for developing personalized therapies, especially in the face of pandemics such as COVID-19. However, this question remains elusive, particularly in primates. In the present study, we aimed to address this question by utilizing monkeys as a model to examine the impacts of social rank on stress levels and physiological and behavioral responses to chronic stress primarily caused by social isolation at both the individual and group levels. Our results showed that high-ranking animals were more susceptible to chronic stress. After exposure to chronic stress, although social hierarchies remained the same, the colonies exhibited more harmonious group relationships (e.g., more prosocial behaviors), with notable contributions from low-ranking animals. Overall, this study deepens our understanding of how social status shapes responses to chronic stress and sheds light on developing tailored and personalized therapies for coping with chronic stress.

Method of measuring effects of study procedures in single and pair housed New Zealand White rabbits (Oryctolagus cuniculus)

Social housing of laboratory rabbits is encouraged and thought to improve animal welfare due to the social nature of this species. However, there is limited published information comparing the physiologic and cardiovascular (CV) effects of paired and single housed adult female rabbits in commonly used laboratory caging. This study describes measurement of heart rate, systolic blood pressure, activity level, body temperature and pairing methods in four female New Zealand White rabbits that were previously implanted with M10 cardiovascular telemetry devices. Data was collected in single housed rabbits having no history of social housing while they were undisturbed in the home cage, during restraint, intramuscular injections and intravenous blood collection. The same animals were then placed in compatible pairs and housed in conventional Allentown caging. As expected, we found increased activity in paired rabbits but no significant differences in body temperatures, and CV parameters in single and paired rabbits undergoing the same procedures. These data suggest that paired rabbits can be used for safety pharmacology studies with minimal impact to data, while supporting improved animal welfare.

Heart rate as a measure of emotional arousal in evolutionary biology

How individuals interact with their environment and respond to changes is a key area of research in evolutionary biology. A physiological parameter that provides an instant proxy for the activation of the automatic nervous system, and can be measured relatively easily, is modulation of heart rate. Over the past four decades, heart rate has been used to assess emotional arousal in non-human animals in a variety of contexts, including social behaviour, animal cognition, animal welfare and animal personality. In this review, I summarize how measuring heart rate has provided new insights into how social animals cope with challenges in their environment. I assess the advantages and limitations of different technologies used to measure heart rate in this context, including wearable heart rate belts and implantable transmitters, and provide an overview of prospective research avenues using established and new technologies, with a special focus on implications for applied research on animal welfare. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Behavioral, metabolic, and renal outcomes of 1-month isolation in adolescent male Dahl salt-sensitive rats

Social contact deficit is considered a stressful circumstance associated with various neural, hormonal, genetic, immune, and behavioral effects. A growing body of clinical and basic science evidence suggests that social isolation is linked to a higher risk of various neurological, cardiovascular, and metabolic diseases, including hypertension, diabetes mellitus, and obesity. However, the impact of the deficit of social interaction on kidney function is not well established. The Dahl salt-sensitive (SS) rat is a classical model of salt-induced hypertension and associated kidney injury. In this study, we investigated the effect of 30 days of social isolation (SI) on blood and urine electrolytes and metabolic, physiological, and behavioral parameters in adolescent male Dahl SS rats fed a normal 0.4% NaCl diet. SI rats demonstrated increased behavioral excitability compared with rats kept in groups. We also observed increased food consumption and a decrease in plasma leptin levels in the SI group without differences in water intake and weight gain compared with grouped animals. No changes in the level of blood and urine electrolytes, 24-h urine output, creatinine clearance, and albumin/creatinine ratio were identified between the SI and grouped rats. These findings indicate that 30 days of social isolation of adolescent Dahl SS rats affects metabolic parameters but has no apparent influence on kidney function.

Psychosocial risk and management of physical diseases

During the 40 years since the Yale conference on Behavioral Medicine and the founding of the Journal of Behavioral Medicine considerable progress has been made in understanding the role of psychosocial risk and management of physical diseases. We here describe the development of these fundamental concepts from early research on stress through studies of the Type A behavior pattern to more contemporary approaches to the relationship between psychosocial risks and benefits in relation to disease processes. This includes the relationship of psychosocial risk to cancers, cardiovascular diseases (CVD), cardiometabolic disorders, Human Immunodeficiency Virus (HIV)/Acquired Human Immune Deficiency Syndrome. During the past 40 years the effects of prolonged distress responses in the pathogenesis of some cancers and CVD have been well-established and modifiable behavioral, cognitive and social factors have been shown to produce favorable outcome components in the management of such diseases as breast cancer, coronary heart disease and HIV.

The Influence of Environmental Enrichment on Cardiovascular and Behavioral Responses to Social Stress

OBJECTIVE

Stress is linked to negative cardiovascular consequences and increases in depressive behaviors. Environmental enrichment (EE) involves exposure to novel items that provide physical and cognitive stimulation. EE has behavioral, cognitive, and neurobiological effects that may improve stress responses in humans and animal models. This study investigated the potential protective effects of EE on behavior and cardiovascular function in female prairie voles after a social stressor.

METHODS

Radiotelemetry transmitters were implanted into female prairie voles to measure heart rate (HR) and heart rate variability (HRV) throughout the study. All females were paired with a male partner for 5 days, followed by separation from their partner for 5 additional days, and a 10-day treatment period. Treatment consisted of continued isolation, isolation with EE, or re-pairing with the partner (n = 9 per group). After treatment, animals were observed in the forced swim test (FST) for measures of stress coping behaviors.

RESULTS

Isolation elevated HR and reduced HRV relative to baseline for all groups (p < .001). HR and HRV returned to baseline in the EE and re-paired groups, but not in the continued isolation group (p < .001). Animals in the EE and re-paired groups displayed significantly lower immobility time (p < .001) and HR (p < .03) during the FST, with a shorter latency for HR to return to baseline levels after the FST, relative to the continued isolation group (p < .001).

CONCLUSIONS

EE and re-pairing reversed the negative behavioral and cardiovascular consequences associated with social isolation.

Role of social interaction, exercise, diet, and age on developing and untreated diabetes in cynomolgus monkeys

Type 2 diabetes mellitus is the most common form of diabetes that occurs in both human and nonhuman primates. Although spontaneously diabetic nonhuman primates are used extensively in diabetic related research and are a proven valuable tool for the study of the natural history of diabetes, little is known about the key factors that can cause this metabolic disorder and the preventative measures that could be employed to minimize the consequences of diabetes. Using a model of developing and untreated diabetes, this study describes the effects of housing arrangement (socially group- versus individually single-housed), exercise, diet, age, and sex on fasting plasma glucose, key lipids associated with diabetes, and bodyweight in two large cohorts of nonhuman primates. Key findings include exercise/housing arrangement's contribution to significant differences in bodyweight, levels of fasting plasma glucose, total cholesterol, and high- and low-density lipoproteins. Age also had profound effects on glucose, triglyceride and high-density lipoproteins, particularly in single-caged animals. Moreover, females had higher fasting glucose, total cholesterol and triglyceride levels than male counterparts within the same housing situations. These factors may be critical to identifying preventive measures that could eventually be used to minimize obesity and diabetes in humans.

Social isolation alters central nervous system monoamine content in prairie voles following acute restraint

Animal models have shown that social isolation and other forms of social stress lead to depressive- and anxiety-relevant behaviors, as well as neuroendocrine and physiological dysfunction. The goal of this study was to investigate the effects of prior social isolation on neurotransmitter content following acute restraint in prairie voles. Animals were either paired with a same-sex sibling or isolated for 4 weeks. Plasma adrenal hormones and ex vivo tissue concentrations of monoamine neurotransmitters and their metabolites were measured following an acute restraint stressor in all animals. Isolated prairie voles displayed significantly increased circulating adrenocorticotropic hormone levels, as well as elevated serotonin and dopamine levels in the hypothalamus, and potentially decreased levels of serotonin in the frontal cortex. However, no group differences in monoamine levels were observed in the hippocampus or raphe. The results suggest that social stress may bias monoamine neurotransmission and stress hormone function to subsequent acute stressors, such as restraint. These findings improve our understanding of the neurobiological mechanisms underlying the consequences of social stress.

Anxiety and new onset of cardiovascular disease: critical review and meta-analysis

BACKGROUND

Anxiety has been associated with new-onset cardiovascular disease (CVD), but the quality of this relationship is unclear. Only if anxiety is a causal, independent cardiovascular risk factor might it be a target for CVD prevention.

AIMS

To determine and examine the independent association and causality between anxiety and incident CVD.

METHOD

PubMed, EMBASE and PsycINFO databases were searched up to October 2013. A review of Hill's criteria for causality and random effects meta-analysis were conducted of prospective, population-based studies examining anxiety and incident CVD in people free from CVD at baseline.

RESULTS

The meta-analysis comprised 37 papers (n = 1 565 699). The follow-up ranged from 1 to 24 years. Anxiety was associated with a 52% increased incidence of CVD (hazard ratio = 1.52, 95% CI 1.36-1.71). The risk seemed independent of traditional risk factors and depression. The evaluation of Hill's criteria largely argued in favour of causality.

CONCLUSIONS

Anxiety may be of interest for CVD prevention. Future research should examine biological and behavioural underpinnings of the association in order to identify targets for intervention.

Adolescent vulnerability to cardiovascular consequences of chronic social stress: Immediate and long-term effects of social isolation during adolescence

It has been demonstrated that disruption of social bonds and perceived isolation (loneliness) are associated with an increased risk of cardiovascular morbidity and mortality. Adolescence is proposed as a period of vulnerability to stress. Nevertheless, the impact of chronic social stress during this ontogenic period in cardiovascular function is poorly understood. Therefore, the purpose of this study was to compare the impact in cardiovascular function of social isolation for 3 weeks in adolescent and adult male rats. Also, the long-term effects of social isolation during adolescence were investigated longitudinally. Social isolation reduced body weight in adolescent, but not in adult animals. Disruption of social bonds during adolescence increased arterial pressure without affecting heart rate and pulse pressure (PP). Nevertheless, social isolation in adulthood reduced systolic arterial pressure and increased diastolic arterial pressure, which in turn decreased PP without affecting mean arterial pressure. Cardiovascular changes in adolescents, but not adults, were followed by facilitation of both baroreflex sensitivity and vascular reactivity to the vasodilator agent acetylcholine. Vascular responsiveness to either the vasodilator agent sodium nitroprusside or the vasoconstrictor agent phenylephrine was not affected by social isolation. Except for the changes in body weight and baroreflex sensitivity, all alterations evoked by social isolation during adolescence were reversed in adulthood after moving animals from isolated to collective housing. These findings suggest a vulnerability of adolescents to the effects of chronic social isolation in cardiovascular function. However, results indicate minimal cardiovascular consequences in adulthood of disruption of social bonds during adolescence.

Effects of group housing on ECG assessment in conscious cynomolgus monkeys

INTRODUCTION

Assessing the cardiovascular safety of new chemical or biological entities is important during pre-clinical development. Electrocardiogram (ECG) assessments in non-human primate (NHP) toxicology studies are often made using non-invasive telemetry systems. We investigated whether ECG recording was feasible during group housing of NHPs, rather than the usual single housed arrangement, and whether it would impact the data collected or affect the ability to detect drug-induced changes in QTc interval.

METHODS

Following a period of acclimatisation to jackets, cynomolgus monkeys (3 males and 3 females) were housed in same sex groups of 3. Female monkeys were administered 4 doses of vehicle whilst male monkeys were administered vehicle, 15, 45 and 135mg/kg moxifloxacin. Each dose was administered on a separate dosing day. The same dosing protocol was repeated with the animals singly housed and the results from the two phases were compared including assessment of statistical power.

RESULTS

Heart rate (HR) was significantly lower, and PR and QT interval significantly higher, at multiple time points when the animals were group housed compared with the singly housed phase. QRS duration and QTc interval were less affected. Moxifloxacin increased QT and QTc intervals but had no consistent effect on HR, QRS duration or PR interval under group housed or singly housed conditions. Power analysis suggested that group housing did not adversely affect the magnitude of detectable changes of ECG parameters. In general, detection of slightly smaller changes was achieved under conditions of group housing.

DISCUSSION

The current study shows group housing to be technically possible during non-invasive ECG recording, resulting in lower resting heart rates and small improvements in sensitivity of detection of drug-induced effects. Given the psychological benefits of group housing for NHPs, it is a refinement that should be considered when conducting ECG assessments in NHP toxicology studies.

Social inequalities in health in nonhuman primates

Overall health has been linked to socioeconomic status, with the gap between social strata increasing each year. Studying the impact of social position on health and biological functioning in nonhuman primates has allowed researchers to model the human condition while avoiding ethical complexities or other difficulties characteristic of human studies. Using female cynomolgus macaques (Macaca fascicularis), our lab has examined the link between social status and stress for 30 years. Female nonhuman primates are especially sensitive to social stressors which can deleteriously affect reproductive health, leading to harmful consequences to their overall health. Subordinates have lower progesterone concentrations during the luteal phase of menstrual cycle, which is indicative of absence or impairment of ovulation. Subordinate animals receive more aggression, less affiliative attention, and are more likely to exhibit depressive behaviors. They also express higher stress-related biomarkers such as increased heart rates and lower mean cortisol. While no differences in body weight between dominant and subordinate animals are observed, subordinates have lower bone density and more visceral fat than their dominant counterparts. The latter increases risk for developing inflammatory diseases. Differences are also observed in neurological and autonomic function. A growing body of data suggests that diet composition may amplify or diminish physiological stress responses which have deleterious effects on health. More experimental investigation of the health effects of diet pattern is needed to further elucidate these differences in an ongoing search to find realistic and long-term solutions to the declining health of individuals living across the ever widening socioeconomic spectrum.

Effects of acute and chronic psychological stress on platelet aggregation in mice

Although psychological stress has long been known to alter cardiovascular function, there have been few studies on the effect of psychological stress on platelets, which play a pivotal role in cardiovascular disease. In the present study, we investigated the effects of acute and chronic psychological stress on the aggregation of platelets and platelet cytosolic free calcium concentration ([Ca(2+)]i). Mice were subjected to both transportation stress (exposure to novel environment, psychological stress) and restraint stress (psychological stress) for 2 h (acute stress) or 3 weeks (2 h/day) (chronic stress). In addition, adrenalectomized mice were subjected to similar chronic stress (both transportation and restraint stress for 3 weeks). The aggregation of platelets from mice and [Ca(2+)]i was determined by light transmission assay and fura-2 fluorescence assay, respectively. Although acute stress had no effect on agonist-induced platelet aggregation, chronic stress enhanced the ability of the platelet agonists thrombin and ADP to stimulate platelet aggregation. However, chronic stress failed to enhance agonist-induced increase in [Ca(2+)]i. Adrenalectomy blocked chronic stress-induced enhancement of platelet aggregation. These results suggest that chronic, but not acute, psychological stress enhances agonist-stimulated platelet aggregation independently of [Ca(2+)]i increase, and the enhancement may be mediated by stress hormones secreted from the adrenal glands.

Premenstrual dysphoria and luteal stress in dominant-social-status female macaques

The current study aims to extend our previous work to develop nonhuman primate model for prospectively studying the mechanism underlying premenstrual dysphoric disorder (PMDD). Thirty young dominant-status female monkeys were randomly divided into the control group, the model group, and JQP group. For two consecutive menstrual cycles, from day 18 to 22, monkeys in the model and JQP groups were housed and immobilized singly in specially designed isolation cages for 5-6 hours per day. At the same time, the pharmaceutical interference effect of jingqianping (JQP) granule, a traditional Chinese medicine specifically used to cure PMDD patients, was tested using monkeys in the JQP group. The behavior and facial expressions of monkeys were photographed with an automatic vidicon and were quantitatively analyzed by "the emotion evaluation scale of female experimental macaque." Changes in serum level of progesterone and estradiol were measured with RIA, and serum level of 5-HT, noradrenaline, and dopamine were measured with HPLC. After experiencing mentioned above stress, 70% of monkeys of model group showed PMDD symptoms during three consecutive menstrual cycles. Estradiol and progesterone serum level decreased (P < 0.01). Moreover, the peak value of secreted hormones in their follicular phase did not occur. Serum level of 5-HT and dopamine were significantly lower (P < 0.01), but the serum noradrenaline level was higher (P < 0.01). Moreover, in monkeys administered by JQP granule, both PMDD symptoms and the anormal serum level of neurotransmitters could be obviously reversed. This special luteal-phase treatment on dominant-social-status monkeys might be a feasible way to create models mimicking PMDD.

Depression-like behavioral phenotypes by social and social plus visual isolation in the adult female Macaca fascicularis

Major depressive disorder (MDD) is a debilitating psychiatric mood disorder that affects millions of individuals globally. Our understanding of the biological basis of MDD is poor, and current treatments are ineffective in a significant proportion of cases. This current situation may relate to the dominant rodent animal models of depression, which possess translational limitations due to limited homologies with humans. Therefore, a more homologous primate model of depression is needed to advance investigation into the pathophysiological mechanisms underlying depression and to conduct pre-clinical therapeutic trials. Here, we report two convenient methods--social isolation and social plus visual isolation--which can be applied to construct a non-human primate model of depression in the adult female cynomolgus monkey (Macaca fascicularis). Both social and social plus visual isolation were shown to be effective in inducing depression-like behavior by significantly reducing socially dominant aggressive conflict behavior, communicative behavior, sexual behavior, and parental behavior. The addition of visual isolation produced more profound behavioral changes than social isolation alone by further reducing parental behavior and sexual behavior. Thus, the degree of behavioral pathology may be manipulated by the degree of isolation. These methods can be applied to construct a non-human primate model of depression in order to assess physiological, behavioral, and social phenomena in a controlled laboratory setting.

Dietary manipulation and social isolation alter disease progression in a murine model of coronary heart disease

BACKGROUND

Mice with a deficiency in the HDL receptor SR-BI and low expression of a modified apolipoprotein E gene (SR-BI KO/ApoeR61(h/h)) called 'HypoE' when fed an atherogenic, 'Paigen' diet develop occlusive, atherosclerotic coronary arterial disease (CHD), myocardial infarctions (MI), and heart dysfunction and die prematurely (50% mortality ~40 days after initiation of this diet). Because few murine models share with HypoE mice these cardinal, human-like, features of CHD, HypoE mice represent a novel, small animal, diet-inducible and genetically tractable model for CHD. To better describe the properties of this model, we have explored the effects of varying the composition and timing of administration of atherogenic diets, as well as social isolation vs. group housing, on these animals.

METHODOLOGY/PRINCIPAL FINDINGS

HypoE mice were maintained on a standard lab chow diet (control) until two months of age. Subsequently they received one of three atherogenic diets (Paigen, Paigen without cholate, Western) or control diet for varying times and were housed in groups or singly, and we determined the plasma cholesterol levels, extent of cardiomegaly and/or survival. The rate of disease progression could be reduced by lowering the severity of the atherogenic diet and accelerated by social isolation. Disease could be induced by Paigen diets either containing or free of cholate. We also established conditions under which CHD could be initiated by an atherogenic diet and then subsequently, by replacing this diet with standard lab chow, hypercholesterolemia could be reduced and progression to early death prevented.

CONCLUSIONS/SIGNIFICANCE

HypoE mice provide a powerful, surgery-free, diet-'titratable' small animal model that can be used to study the onset of recovery from occlusive, atherosclerotic CHD and heart failure due to MI. HypoE mice can be used for the analysis of the effects of environment (diet, social isolation) on a variety of features of cardiovascular disease.

The hypothalamic-pituitary-adrenal axis and sex hormones in chronic stress and obesity: pathophysiological and clinical aspects

Obesity, particularly the abdominal phenotype, has been ascribed to an individual maladaptation to chronic environmental stress exposure mediated by a dysregulation of related neuroendocrine axes. Alterations in the control and action of the hypothalamic-pituitary-adrenal axis play a major role in this context, with the participation of the sympathetic nervous system. The ability to adapt to chronic stress may differ according to sex, with specific pathophysiological events leading to the development of stress-related chronic diseases. This seems to be influenced by the regulatory effects of sex hormones, particularly androgens. Stress may also disrupt the control of feeding, with some differences according to sex. Finally, the amount of experimental data in both animals and humans may help to shed more light on specific phenotypes of obesity, strictly related to the chronic exposure to stress. This challenge may potentially imply a different pathophysiological perspective and, possibly, a specific treatment.

Behavioral and neurobiological characteristics of social stress versus depression in nonhuman primates

The focus of the review is on the behavioral and physiological manifestations of stress versus depression. The purpose of the review is to evaluate the conceptual approach of using stress models as surrogates for depression. Social stress and depression have many characteristics in common and promote each other. Both have adverse effects on social relationships and the quality of life, and increase risk of other diseases. However, they are not the same constructs. In human and nonhuman primates, the behavior and neurobiology of stressed individuals differ from that of depressed individuals. Some similarities in stress physiology in socially stressed and depressed individuals have been used to support the use of stressed animals as models of depression, and much has been learned from stress models of depression. However, the studies reviewed here also suggest that the depressed state also has different characteristics than the stressed state, and studying the differences may be important to furthering our understanding of each of these constructs as well as their mutual relationship.

Better safe than sorry--socio-spatial group structure emerges from individual variation in fleeing, avoidance or velocity in an agent-based model

In group-living animals, such as primates, the average spatial group structure often reflects the dominance hierarchy, with central dominants and peripheral subordinates. This central-peripheral group structure can arise by self-organization as a result of subordinates fleeing from dominants after losing a fight. However, in real primates, subordinates often avoid interactions with potentially aggressive group members, thereby preventing aggression and subsequent fleeing. Using agent-based modeling, we investigated which spatial and encounter structures emerge when subordinates also avoid known potential aggressors at a distance as compared with the model which only included fleeing after losing a fight (fleeing model). A central-peripheral group structure emerged in most conditions. When avoidance was employed at small or intermediate distances, centrality of dominants emerged similar to the fleeing model, but in a more pronounced way. This result was also found when fleeing after a fight was made independent of dominance rank, i.e. occurred randomly. Employing avoidance at larger distances yielded more spread out groups. This provides a possible explanation of larger group spread in more aggressive species. With avoidance at very large distances, spatially and socially distinct subgroups emerged. We also investigated how encounters were distributed amongst group members. In the fleeing model all individuals encountered all group members equally often, whereas in the avoidance model encounters occurred mostly among similar-ranking individuals. Finally, we also identified a very general and simple mechanism causing a central-peripheral group structure: when individuals merely differed in velocity, faster individuals automatically ended up at the periphery. In summary, a central-peripheral group pattern can easily emerge from individual variation in different movement properties in general, such as fleeing, avoidance or velocity. Moreover, avoidance behavior also affects the encounter structure and can lead to subgroup formation.

The effects of a long-term psychosocial stress on reproductive indicators in the baboon

Psychosocial stress is thought to negatively impact fecundity, but human studies are confounded by variation in nutrition and lifestyle. Baboons offer a useful model to test the effect of prolonged mild stress on reproductive indicators in a controlled setting. Following relocation from social groups to solitary housing, a previously documented stressful event for nonhuman primates, daily urine samples, tumescence, and menstrual bleeding were monitored in twenty baboons (Papio sp.) for 120-150 days. Specimens were assayed for estrone conjugates (E1C), pregnanediol-3-glucuronide (PDG), follicle-stimulating hormone (FSH), and cortisol. Linear mixed effects models examined (1) the effects of stress on frequency of anovulation, hormone levels, tumescence and cycle length, and (2) the relationship of cortisol with reproductive indicators. Despite cortisol levels indicative of stress, anovulation was negligible (1% in 102 cycles). PDG, FSH, cycle length, and tumescence declined during the first four cycles, but began recovery by the fifth. Cortisol was negatively associated with FSH but not associated with PDG, E1C or tumescence. Ovulation, E1C, and luteal phase length were not affected. Tumescence tracked changes in FSH and PDG, and thus may be a useful indicator of stress on the reproductive axis. Elevated cortisol was associated with reduced FSH, supporting a model of cortisol action at the hypothalamus rather than the gonad. After four to five menstrual cycles the reproductive indicators began recovery, suggesting adjustment to new housing conditions. In conclusion, individual housing is stressful for captive baboons, as reflected by cortisol and reproductive indicators, although ovulation, a relatively direct proxy for fecundity, is unaffected.

Types of social capital resources and self-rated health among the Norwegian adult population

Background

Social inequalities in health are large in Norway. In part, these inequalities may stem from differences in access to supportive social networks - since occupying disadvantaged positions in affluent societies has been associated with disposing poor network resources. Research has demonstrated that social networks are fundamental resources in the prevention of mental and physical illness. However, to determine potentials for public health action one needs to explore the health impact of different types of network resources and analyze if the association between socioeconomic position and self-rated health is partially explained by social network factors. That is the aim of this paper.

Methods

Cross-sectional data were collected in 2007, through a postal survey from a gross sample of 8000 Norwegian adults, of which 3,190 (about 40%) responded. The outcome variable was self-rated health. Our main explanatory variables were indicators of socioeconomic positions and social capital indicators that was measured by different indicators that were grouped under 'bonding', 'bridging' and 'linking' social capital. Demographic data were collected for statistical control. Generalized ordered logistic regression analysis was performed.

Result

Results indicated that those who had someone to talk to when distressed were more likely to rate their health as good compared to those deprived of such person(s) (OR: 2.17, 95% CI: 1.55, 3.02). Similarly, those who were active members in two or more social organisations (OR: 1.73, 95% CI: 1.34, 2.22) and those who count a medical doctor among their friends (OR: 1.51, 95% CI: 1.13, 2.00) report better health. The association between self-rated health and socio-economic background indicators were marginally attenuated when social network indicators were added into the model.

Conclusion

Among different types of network resources, close and strong friendship-based ties are of importance for people's health in Norway. Networks linking people to high-educated persons are also of importance. Measures aiming at strengthening these types of network resources for socially disadvantaged groups might reduce social inequalities in health.

Neighborhood psychosocial hazards and cardiovascular disease: the Baltimore Memory Study

OBJECTIVES

We examined associations between cardiovascular disease and neighborhood psychosocial hazards, such as violent crime, abandoned buildings, and signs of incivility, to evaluate whether features of place are associated with older adult health.

METHODS

We analyzed first-visit data from the Baltimore Memory Study of randomly selected residents aged 50 to 70 years (n=1140) of 65 contiguous neighborhoods in Baltimore, Maryland. We looked for associations between self-reports of history of selected cardiovascular diseases and scores on the 12-item neighborhood psychosocial hazards scale.

RESULTS

After adjustment for established individual risk factors for cardiovascular disease, residents in neighborhoods with scores in the highest quartile of the psychosocial hazards scale had more than 4 times higher odds of a history of myocardial infarction and more than 3 times higher odds of myocardial infarction, stroke, transient ischemic attack, or intermittent claudication compared with residents living in neighborhoods scoring in the lowest quartile.

CONCLUSIONS

Neighborhood psychosocial hazards were significantly associated with self-reported cardiovascular disease after adjustment for individual-level risk factors. This is consistent with the hypothesis that environmental stress plays a role in the etiology of cardiovascular disease.

Isolating with physical restraint low status female monkeys during luteal phase might make an appropriate premenstrual depression syndrome model

BACKGROUND

Rhesus monkeys (Macaca mulatta) have a close phylogenetic relationship to humans, and have a similar 28-day menstrual cycle with similar hormonal fluctuations. In this study, we attempt to establish the premenstrual depression syndrome of rhesus monkey (M. mulatta) models by isolation with physical restraint of low social status young female monkeys during their luteal phase.

METHODS

Low social status young female rhesus monkeys (M. mulatta) were isolated with physical restraint during their luteal phase by using a specifically designed isolating-cage. During the entire menses cycle, serum levels of 5-hydroxytrypamine, noradrenalin and adrenalin were detected by capillary zone electrophoresis, and the changes in the serum levels of progesterone, estradiol and prolactin were investigated by radioimmunoassay. At the same time, the pharmaceutical interference effect of Jingqianshu granule, a traditional Chinese medicine specifically used to cure premenstrual depression patients, was tested using this premenstrual depression syndrome monkey model.

RESULTS

After being immured in two consecutive menstrual cycles, monkeys presented depressive symptoms during the premenstrual phase of three consecutive menstrual cycles. The serum contents of the three kinds of monoamine neurotransmitters in depressive monkeys were significantly higher than the normal ones. The serum levels of progesterone and prolactin increased obviously, and a marked change in the pattern of progesterone secretion could be observed. Moreover, the premenstrual depressive symptoms of model group monkeys could not only be cured by Jingqianshu granule, but the higher serum levels of prolactin and monoamine neurotransmitters in these monkeys could be reduced by this herbal medicine. These data were well in line with clinical observations of women with premenstrual depression syndrome.

CONCLUSION

Our results in this study for the first time indicate that isolation with physical restraint of low status young female monkeys during their luteal phase makes an appropriate premenstrual depression syndrome model. This model might potentially facilitate studies on the etiology of premenstrual depression syndrome and the development of better methods for the therapy of this disease.

Danish singles have a twofold risk of acute coronary syndrome: data from a cohort of 138 290 persons

STUDY OBJECTIVE

Atherosclerosis of the coronary and other arteries is an important health problem in virtually all countries of the world, and thus there is a persisting need for the development of preventive programmes including population risk group identification. The aim of the study was to identify sociodemographic population risk indicators of an initial episode of acute coronary syndrome (ACS), including unstable angina pectoris (UAP), myocardial infarction (MI), and sudden cardiac death (SCD).

DESIGN

Cohort study of 138 290 residents of the municipality of Aarhus, Denmark, aged 30-69 years. Information on population members' individual age, sex, social background, and eventual death was obtained from Danish Population Registers.

SETTING

University hospital.

PATIENTS

The study prospectively identified 646 victims of ACS from 1 April 2000 to 31 March 2002.

MAIN RESULTS

Based on multiple logistic regression, age and single living were found to be positively associated with incident ACS in both sexes. Women >60 years living alone and men >50 years living alone were at especially high risk. They constituted only 5.4% and 7.7% of the source population, respectively, but they accounted for 34.3% and 62.4% of ACS patients dying within 30 days.

CONCLUSIONS

Single living is associated with an increased risk of ACS. Thus, risk groups identified by use of information on their age and family structure may be targets for future more focused and cost effective preventive strategies. In Western populations, such high risk groups will constitute comparatively limited parts of the population, and in Denmark they are easily identifiable in routine population registers.

The metabolic syndrome, depression, and cardiovascular disease: interrelated conditions that share pathophysiologic mechanisms

This article introduces the metabolic syndrome as a clinical phenotype with consequences for diagnosis and treatment that go beyond the different clinical specialties involved. A life-course approach is suggested as a means of understanding the complex interrelations between the metabolic syndrome, depression, and cardiovascular disease. Pathophysiologic mechanisms that these conditions share are discussed in detail. These considerations provide arguments for a more integrative approach to patients in general that surpass the current disease-centered services such as endocrinology, psychiatry, and cardiology.

Impact of social environment on female chimpanzee reproductive cycles

The socio-sexual environment of a female is known to affect ovarian function. Increased male contact can enhance menstrual cycle regularity. Conversely, social deprivation constitutes a form of stress that often alters cyclicity and the secretion of reproductive hormones. The present study was carried out on captive female chimpanzees to examine possible interactions among housing conditions, menstrual cycle length, morphological changes in secondary sexual character expression and endocrine release patterns related to follicular and luteal function. Animals were housed over a period of 2 years either with a male conspecific or singly. Blood samples were collected over three cycles, and anogenital swelling changes registered to define menstrual cycle phases. Fecal sampling techniques were used to monitor cortisol as a measure of stress-load. Male presence seemed to affect female cyclicity. Females housed with a male had shorter and more regular cycles than singly housed females. Prolactin, gonadotropins and estradiol levels were generally higher in paired females during specific cycle phases. Group variation was not always significant. No differences were found in progesterone. Sexually cohabited females tended to have lower fecal cortisol metabolites immediately before and after maximum tumescence. We suggest that the close behavioral, physical and olfactory contact with a male conspecific can act as a sort of zeitgeber to modulate ovarian function by stabilizing the female cycle and, perhaps, enhancing folliculogenesis and ovulation.

Social network diversity and risks of ischemic heart disease and total mortality: findings from the Copenhagen City Heart Study

Measures of various types of social contacts were used as predictors of ischemic heart disease events and total mortality in an age-stratified random sample of 9,573 adults enrolled in the Copenhagen City Heart Study (Copenhagen, Denmark). Baseline examinations were conducted in 1991-1994, and participants were followed until the end of 1997. Contacts with parents, children, family members, and friends were associated with better health. The presence of a spouse or partner was protective for men. Contacts with neighbors showed a trend toward a reversed pattern, and the effects of contacts with work colleagues and children differed by gender. Most types of contacts that occurred at least monthly were just as protective as those occurring more frequently. An index of intimate social contact diversity with family and friends had graded relations with both outcomes. Comparisons of persons reporting three or more types of contacts with those reporting fewer types yielded age- and gender-adjusted hazard ratios of 0.73 (95% confidence interval (CI): 0.64, 0.82) for mortality and 0.75 (95% CI: 0.61, 0.91) for ischemic heart disease. Comparable fully adjusted hazard ratios were 0.83 (95% CI: 0.73, 0.95) and 0.82 (95% CI: 0.67, 1.00). These data suggest that health benefits are derived from the diversity of social roles, especially those involving intimate relationships.

Psychosocial factors and cardiovascular diseases

Rapidly accruing evidence from a diversity of disciplines supports the hypothesis that psychosocial factors are related to morbidity and mortality due to cardiovascular diseases. We review relevant literature on (a) negative emotional states, including depression, anger and hostility, and anxiety; (b) chronic and acute psychosocial stressors; and (c) social ties, social support, and social conflict. All three of these psychosocial domains have been significantly associated with increased risk of cardiovascular morbidity and mortality. We also discuss critical pathophysiological mechanisms and pathways that likely operate in a synergistic and integrative way to promote atherogenesis and related clinical manifestations. We conclude by discussing some of the important challenges and opportunities for future investigations.

Social isolation stress impairs the resistance of mice to experimental liver metastasis of murine colon 26-L5 carcinoma cells

Our previous study has demonstrated that the exposure of male BALB/c mice to social isolation stress caused a suppressed immune response and enhanced liver metastasis of colon 26-L5 carcinoma cells. To more precisely understand the influence of psychosocial factors on the metastatic process, here we have investigated the effect of social isolation stress on the vulnerability of the host to develop liver metastasis of colon 26-L5 cells, including the time span and incidence of metastatic formation, survival time and chemotherapy response. Isolation stress decreased the time period required for the metastasis formation relative to that in controls. On day 7 after the tumor injection, the 75% incidence of tumor metastasis in the stressed mice was 5 times the 15% incidence in the unstressed mice. When exposed to the challenge of lower cell numbers (0.025, 0.05, 0.1 x 10(4)/mouse) of colon 26-L5 cells, mice subjected to isolation stress developed an elevated incidence of metastasis (33.3, 66.6, and 100%, respectively) as compared with the controls (0, 33.3 and 50%, respectively). The survival time following the tumor inoculation was also shorter in the stressed mice (21.83 +/- 1.59d) than in the control mice (24.08 +/- 1.68 d). Furthermore, the response of liver metastasis to chemotherapy consisting of 2 mg/kg cisplatin (CDDP) was worse in the stressed mice than that in unstressed mice. These findings suggested that social isolation stress could significantly impair the resistance of mice to the development of metastasis.

Stress-induced blood pressure reactivity and incident stroke in middle-aged men

BACKGROUND AND PURPOSE

Exaggerated blood pressure reactivity to stress is associated with atherosclerosis and hypertension, which are known stroke risk factors, but its relation to stroke is unknown. Previous work also indicates that the association between reactivity and cardiovascular diseases may be influenced by socioeconomic status.

METHODS

The impact of blood pressure reactivity and socioeconomic status on incident stroke was examined in 2303 men (mean age, 52.8+/-5.1 years) from a population-based, longitudinal study of risk factors for ischemic heart disease in eastern FINLAND: Reactivity was calculated as the difference between blood pressure measured during the anticipatory phase of an exercise tolerance test (before exercise) and resting blood pressure, measured 1 week earlier. Mean systolic reactivity was 20 mm Hg (+/-15.9), and mean diastolic reactivity was 8.6 mm Hg (+/-8.5). Socioeconomic status was assessed as years of education. One hundred thirteen incident strokes (90 ischemic) occurred in 11.2 (+/-1.6) years of follow-up.

RESULTS

Men with exaggerated systolic reactivity (>/=20 mm Hg) had 72% greater risk of any stroke (relative hazard ratio [RH], 1.72; 95% CI, 1.17 to 2.54) and 87% greater risk of ischemic stroke (RH, 1.87; 95% CI, 1.20 to 2.89) relative to less reactive men. Moreover, men who were high reactors and poorly educated were nearly 3 times more likely to suffer a stroke than better educated, less reactive men (RH, 2.90; 95% CI, 1.66 to 5.08). Adjustment for stroke risk factors had little impact on these associations. Diastolic reactivity was unrelated to stroke risk.

CONCLUSIONS

Excessive sympathetic reactivity to stress may be etiologically important in stroke, especially ischemic strokes, and low socioeconomic status confers added risk.

Partner interactions are associated with reduced blood pressure in the natural environment: ambulatory monitoring evidence from a healthy, multiethnic adult sample

OBJECTIVE

The objective of this study was to examine the effects of partner interactions on ambulatory blood pressure in a sample of 120 healthy adults who were monitored over a 6-day period.

METHODS

After each blood pressure measurement, participants rated characteristics of ongoing social interactions, along with emotional activation, physical activity, talking, posture, and other covariates, with computer-assisted self-report assessments.

RESULTS

Using multilevel modeling, we showed that blood pressure was significantly lower during social interactions with one's partner relative to social interactions with any other person and relative to periods of not interacting. Interactions with partners also were characterized by significantly less talking and emotional activation and more intimacy and perceived emotional support; however, these differences did not mediate the partner effect on blood pressure. In addition, the relative benefits of interacting with a partner were not moderated by relationship quality, gender, or race.

CONCLUSIONS

The effects of social situations on ambulatory blood pressure may represent one pathway through which social relationships affect cardiovascular health. Key words: blood pressure, social interaction, partner interactions, cardiovascular health.

Social isolation stress enhanced liver metastasis of murine colon 26-L5 carcinoma cells by suppressing immune responses in mice

We investigated the effect of social isolation stress on the formation of experimental liver metastasis resulted from intraportal vein (i.p.v.) injection of colon 26-L5 carcinoma cells in male Balb/c mice, and elucidated some of the underlying mechanism involving the effects of this stress on cellular immunity. Increases in the colony number and tumor burden were observed in the mice socially isolated before and/or after tumor cell challenge, as compared with the group-housed mice. In addition, exposure of mice to 2 weeks of preisolation resulted in decreases in the thymus weight and number of thymocytes by 35.8% and 40.2%, respectively, in comparison with the controls. Reduced proliferative response of splenocytes to various stimuli and suppressed splenic NK activity, as well as decreased macrophage-mediated cytotoxicity, were also found in the mice exposed to social isolation. Thus, these results suggest that social isolation stress enhances tumor metastasis in part via its suppressive effect on the immune system of the host.

The effects of the social environment on stress-related cardiovascular activation: current findings, prospects, and implications

Social relationships have been shown to be health-protective and to improve cardiovascular disease prognosis. One of the mechanisms by which social relationships may alter health status is through altering patterns of neuroendocrine or hemodynamic responding to ongoing activity. For example, research with non-human primates suggests that disrupted social relationships may increase cardiovascular risk through their effects on sympathetic nervous system activation. In humans, a number of recent reports have shown that the presence of an affiliative companion can reduce cardiovascular activity during psychologically challenging tasks, results which are consistent with this proposed mechanism of effect. We review the recent human literature which has examined the effects of the social environment on stress-related cardiovascular activity. Although findings in this literature are generally consistent, recent anomalous results are reviewed which shed light on some of the context-dependent effects of social affiliation. Additional areas for further investigation are examined, including possible mechanisms for explaining these social affiliation effects, individual differences which may moderate these effects, and emerging methodological advances for examining how these effects may generalize to the natural environment.

Impact of psychological factors on the pathogenesis of cardiovascular disease and implications for therapy

Recent studies provide clear and convincing evidence that psychosocial factors contribute significantly to the pathogenesis and expression of coronary artery disease (CAD). This evidence is composed largely of data relating CAD risk to 5 specific psychosocial domains: (1) depression, (2) anxiety, (3) personality factors and character traits, (4) social isolation, and (5) chronic life stress. Pathophysiological mechanisms underlying the relationship between these entities and CAD can be divided into behavioral mechanisms, whereby psychosocial conditions contribute to a higher frequency of adverse health behaviors, such as poor diet and smoking, and direct pathophysiological mechanisms, such as neuroendocrine and platelet activation. An extensive body of evidence from animal models (especially the cynomolgus monkey, Macaca fascicularis) reveals that chronic psychosocial stress can lead, probably via a mechanism involving excessive sympathetic nervous system activation, to exacerbation of coronary artery atherosclerosis as well as to transient endothelial dysfunction and even necrosis. Evidence from monkeys also indicates that psychosocial stress reliably induces ovarian dysfunction, hypercortisolemia, and excessive adrenergic activation in premenopausal females, leading to accelerated atherosclerosis. Also reviewed are data relating CAD to acute stress and individual differences in sympathetic nervous system responsivity. New technologies and research from animal models demonstrate that acute stress triggers myocardial ischemia, promotes arrhythmogenesis, stimulates platelet function, and increases blood viscosity through hemoconcentration. In the presence of underlying atherosclerosis (eg, in CAD patients), acute stress also causes coronary vasoconstriction. Recent data indicate that the foregoing effects result, at least in part, from the endothelial dysfunction and injury induced by acute stress. Hyperresponsivity of the sympathetic nervous system, manifested by exaggerated heart rate and blood pressure responses to psychological stimuli, is an intrinsic characteristic among some individuals. Current data link sympathetic nervous system hyperresponsivity to accelerated development of carotid atherosclerosis in human subjects and to exacerbated coronary and carotid atherosclerosis in monkeys. Thus far, intervention trials designed to reduce psychosocial stress have been limited in size and number. Specific suggestions to improve the assessment of behavioral interventions include more complete delineation of the physiological mechanisms by which such interventions might work; increased use of new, more convenient "alternative" end points for behavioral intervention trials; development of specifically targeted behavioral interventions (based on profiling of patient factors); and evaluation of previously developed models of predicting behavioral change. The importance of maximizing the efficacy of behavioral interventions is underscored by the recognition that psychosocial stresses tend to cluster together. When they do so, the resultant risk for cardiac events is often substantially elevated, equaling that associated with previously established risk factors for CAD, such as hypertension and hypercholesterolemia.

Social isolation and cardiovascular disease: an atherosclerotic pathway?

This paper outlines two pathways through which social support can influence the prevention or progression of cardiovascular disease: health behaviors and neuroendocrine mechanisms. Its primary focus is on neuroendocrine pathways, reviewing data which suggest that lack of social support is etiologically related to coronary artery lesion development through two mechanisms: sympathetic-adrenomedullary influences on platelet function, heart rate and blood pressure in the initial endothelial injury; and pituitary-adrenal cortical factors involved in smooth muscle cell proliferation during progression of the lesion after injury has taken place. It hypothesizes that the buffering effect of social support on the cardiovascular system is mediated primarily through mechanisms associated with the release of oxytocin.

Behavioral and neurobiological effects of estrogen replacement therapy and a history of triphasic oral contraceptive exposure

The effects of contraceptive steroids and estrogen replacement therapy on behavior and neuroendocrine function were evaluated in adult female cynomolgus monkeys. During the 'premenopausal' phase of the experiment, the animals were assigned to either treatment with a triphasic oral contraceptive (OC) for 24 months or the untreated control group. The monkeys were then ovariectomized and half of each of the premenopausal groups were randomly assigned to either treatment with conjugated equine estrogens (ERT) or the untreated control group for 12 months (the 'postmenopausal' phase). All evaluations were completed during the postmenopausal phase of the experiment. Both types of exogenous steroid treatments appeared to increase cardiovascular and hypothalamic-pituitary-adrenal responses to stress in socially dominant but not socially subordinate females. A history of triphasic OC administration increased contact aggression received, and reduced the prolactin response to fenfluramine, suggesting reduced serotonergic activity, for at least a year following the cessation of triphasic OC treatment.