Supplementary Material for: Which Social Network or Support Factors are Associated with Cognitive Abilities in Old Age?

<b><i>Background:</i></b> Social networks and support have been proposed as cognitively protective in old age. As studies often consider these social factors in isolation the question of which characteristics of the social environment are beneficial remains. <b><i>Objective:</i></b> The current study examined associations between measures of social networks (including contact with friends/family, marital status and living arrangement), feelings of loneliness and social support, and a range of cognitive outcomes. <b><i>Methods:</i></b> Social network, loneliness and support data were available in the Lothian Birth Cohort 1936 (LBC1936, n = 1,091) at age 70. Participants completed a battery of cognitive tests, and factor scores were available for general cognitive ability, and the cognitive domains of processing speed and memory. Childhood cognitive ability data from age 11 were also available. <b><i>Results:</i></b> When examined in separate ANCOVAs, lower loneliness and more social support were significantly associated with better cognitive abilities at age 70, though not memory (independently of age, sex, childhood cognitive ability and social class), accounting for about 0.5-1.5% of the variance. When the social factors were considered simultaneously, higher loneliness remained associated with lower general cognitive ability (η<sub>p</sub><sup>2</sup> = 0.005, p = 0.046), and those living alone (η<sub>p</sub><sup>2</sup> = 0.007, p = 0.014) or with less social support (η<sub>p</sub><sup>2</sup> = 0.007, p = 0.016) had slower processing speed. When these final models were repeated including a depression symptoms score as a covariate, the associations between loneliness and general cognitive ability, and social support and processing speed, were no longer significant. However, the association between living alone and processing speed remained (η<sub>p</sub><sup>2</sup> = 0.006, p = 0.031). <b><i>Conclusions:</i></b> Of the social factors considered, loneliness, social support and living arrangement were most consistently associated with aspects of cognitive ability in older people, and these associations appeared to be partly, though not wholly, accounted for by symptoms of depression. Although longitudinal follow-up is required to examine the causal direction of the effects more definitively, it may be beneficial to promote the development of interventions to reduce loneliness and social isolation, and to increase social support.