The importance of social relationships in the process of cognitive ageing

Due to ageing populations worldwide, the number of people with cognitive impairments and dementia is increasing rapidly. Insight in the risk factors is crucial in order to develop interventions that prevent or delay the development of the disease. We investigated to what extent social functioning is associated with cognitive decline. Three stages of cognitive decline are considered, including subjective memory complaints, cognitive decline and dementia.The findings in this PhD thesis show that multiple aspects of social functioning are associated with different stages of cognitive decline. Better feelings of affection and behavioral confirmation protect against the development of subjective memory complaints and contribute to the recovery thereof. In addition, people recovered more often from subjective memory complaints if they were in a relationship, had a larger family composition, and had better feelings of status. Poor social relationships were also associated with cognitive decline. This was found for both the structure (e.g. small social network or low frequency of social contact), and the function (e.g. low social support and feelings of loneliness) of social relations. Particularly a lack of social interaction is associated with incident dementia. This effect is of comparable strength as other well-established risk factors for dementia, such as physical inactivity, smoking, and depression.It is well-known that non-smoking, a healthy diet and physical activity reduce the risk of cognitive decline. Our findings show that better social functioning should be added to this list. This is an important fact for GPs, geriatricians or policymakers who may still wonder whether promoting social interaction could be beneficial. We therefore advocate that more attention is paid to social functioning in the prevention of dementia