Kawachi I, Colditz GA, Ascherio A, Rimm EB, Giovannucci E, Stamfer MF, Willett WC. A prospective study of social networks in relation to total mortality and cardiovascular disease in men in the USA. Journal of Epidemiology and Community Health 1996; 50: 245-251

Durkheim first suggested that there was more suicide in socially isolated individuals. Social isolated has been shown to be associated with higher mortality in general, but questions remain whether this is more true for specific illnesses or is a general finding independent of illness. This study suggested that the occurrence (incidence) of some illnesses such as heart disease may not depend on social networks, though survival from them may. It also demonstrated that social networks appeared to have a protective effect on the occurrence of strokes. The authors discuss four potential pathways through which social relationships might affect health. These include: provision of instrumental support such as financial assistance or services in kind; provision of information and advice to assist individuals in seeking care or adopting health promoting behaviors; providing emotional support; and directly influencing host resistance and susceptibility to disease through alterations in neuroendocrine and immunological control systems. [For the income inequality health relationship, this study is important in demonstrating one possible mechanism through which income inequality may work, namely its affects on social networks, and social cohesion. The difficulties of looking at different kinds of stress and their affect on health of populations are brought out in the discussion section. Kawachi's group has found in an ecologic study cited in D above that income inequality works through social cohesion, which is related to the social networks discussed here. ] 

Abstract

STUDY OBJECTIVE: Previous studies have established a relationship between low levels of social networks and total mortality, but few have examined cause specific mortality or disease incidence. This study aimed to examine prospectively the relationships between social networks and total and cause specific mortality, as well as cardiovascular disease incidence. 

DESIGN: This was a four year follow up study in an ongoing cohort of men, for whom information on social networks was collected at baseline. The main outcome measures were total mortality, further categorised into deaths from cardiovascular disease (stroke and coronary heart disease), total cancer, accidents/suicides, and all other causes; as well as stroke and coronary heart disease incidence. 

PARTICIPANTS: Altogether 32,624 US male health professionals aged 42 to 77 years in 1988, who were free of coronary heart disease, stroke, and cancer at baseline. 

RESULTS: A total of 511 deaths occurred during 122,911 person years of follow up. Compared with men with the highest level of social networks, socially isolated men (not married, fewer than six friends or relatives, no membership in church or community groups) were at increased risk for cardiovascular disease mortality (age adjusted relative risk, 1.90; 95% CI 1.07, 3.37) and deaths from accidents and suicides (age adjusted relative risk 2.22; 95% CI 0.76, 6.47). No excess risks were found for other causes of death. Socially isolated men were also at increased risk of stroke incidence (relative risk, 2.21; 95% CI, 1.12, 4.35), but not incidence of non-fatal myocardial infarction.

CONCLUSIONS: Social networks were associated with lower total mortality by reducing deaths from cardiovascular disease and accidents/suicides. Strong social networks were associated with reduced incidence of stroke, though not of coronary heart disease. However, social networks may assist in prolonging the survival of men with established coronary heart disease.

Keywords

• atherosclerosis
• behavioral factors
• cause specific mortality
• heart disease
• income inequality
• mortality
• psychosocial factors
• risk factor
• social cohesion
• social networks
• socioeconomic status
• stress
• suicide