Tools for advancing research into social networks and cognitive function in older adults

People are good for your brain. Decades of research have shown that individuals who have a larger number of people in their social network or higher quality ties with individuals within their network have lower rates of morbidity and mortality across a wide range of health outcomes. Among these outcomes, cognitive function, especially in the context of brain aging, has been one area of particular interest with regard to social engagement, or more broadly, socially integrated lifestyles. Many studies have observed an association between the size of a person’s social network or levels of social engagement and the risk for cognitive decline or dementia (e.g. see review by Fratiglioni et al., 2004). The dementia risk reduction associated with a larger social network or social engagement shown by some epidemiological studies is fairly large. The population effect size of increasing social engagement on delaying dementia disease progression could exceed that of current FDA approved medications for Alzheimer’s disease. The positive effects of social interactions and engagement on cognitive function have been demonstrated even at the level of biomarkers. For example, recent MRI studies found associations between the size and complexity of real-world social networks and the density of gray matter (Kanai et al., 2012) and amygdala volume (Bickart et al., 2011). Possible modifiable effects of larger social networks on symptomatic outcomes of Alzheimer’s disease pathologies have also been shown (Bennett et al., 2006). Human epidemiological studies are not free from possible reverse causations such as lower levels of social engagement being the result of presymptomatic dementia, not the cause of dementia. However, non-human research suggests that social network size could actually contribute to changes both in brain structure and function, providing further support for causal links (Sallet et al., 2011).