Lack of social support has shown to be a major risk factor for poor health, mortality, and dementia. We analyzed what factors drive the likelihood of having restricted social networks and to what extent those factors then influence the risk of developing dementia. Our results from the Leipzig Longitudinal Study of the Aged (LEILA75+) indicate that older age (odds ratio [OR]: 1.04) and living with other people (OR: 2.12) was associated with a greater likelihood of having a restricted social network. A better cognitive status (OR: 0.84) was associated with a smaller likelihood of having a restricted social network. The risk of developing dementia over the follow-up period was significantly higher among individuals with restricted (hazard ratio: 2.11) than with integrated social networks. Our findings suggest that integrating elderly individuals in the wider community is a crucial indicator for dementia risk.