Review of the Association Between Number of Social Roles and Cardiovascular Disease: Graded or Threshold Effect?

There is increasing evidence for an inverse association between the number of social roles (e.g., spouse, friend, and neighbor) we engage in and our risk of disease, especially cardiovascular disease (CVD). Two mechanistic models have been proposed to explain this association. The social integration model refers to a graded association where every additional social role is associated with an increase in resistance to disease. The social isolation model refers to a threshold effect where the lack of a minimal criterion number of roles increases risk of disease. We conducted a systematic review of prospective studies examining the association between number of social roles and CVD risk. When we include all studies assessing number of social roles, irrespective of whether associations are attributable to graded effects (social integration) and threshold effects (social isolation) or cannot be determined by the data presented, those holding fewer social roles were found to be at greater risk of CVD incidence, CVD mortality (evidence stronger for men than women), and greater progression of disease (only for short [≤5 years] follow-ups). However, closer analyses indicate that the association between a greater number of social roles and decreased CVD incidence was attributable to graded effects among men but to both effects among women. In contrast, the association of number of social roles and disease progression was driven by threshold effects (social isolation) for both sexes, whereas mortality studies included evidence for both effects. These results suggest underlying mechanisms linking social roles to different CVD outcomes.