Figure 2.

Socially isolated individuals exhibit higher levels of the clotting factor fibrinogen. Panel (a) shows the fibrinogen (mg per 100 ml) and indegree values for Wave 5 of the Framingham Offspring Study (n = 3568 with fibrinogen measurements). Individuals nominated more often as friends and family members have lower levels of the clotting factor fibrinogen (r = −0.14, p < 0.0001). Points are jittered horizontally to better depict the density of the data around discrete values of indegree. Panel (b) shows the largest connected subcomponent of the social network, containing 66.0% of the individuals in the whole network. Of the 14 942 individuals in the largest component, 2451 (16.4%) have fibrinogen measurements. Redder colouring indicates higher fibrinogen levels, and yellower colouring indicates lower fibrinogen levels. Nodes in the component without fibrinogen measurements (used for calculation of centrality measures and for layout of the graph) are depicted minimally in pale grey. Node size is proportional to indegree. The network is laid out using the Fruchterman–Reingold algorithm, tuned for greater repulsion between nodes. Low-fibrinogen (yellower) individuals tend to have higher indegree (larger diameter) and to be globally or locally central, whereas a preponderance of high-fibrinogen (redder) individuals have lower indegree (smaller diameter) and are relatively more isolated in the social network.