Positive and negative experiences of social support and risk of dementia in later life: An investigation using the English Longitudinal Study of Ageing

Background: Having a network of close relationships may reduce the risk of developing dementia. However, social exchange theory suggests that social interaction entails both rewards and costs. The effects of quality of close social relationships in later life on the risk of developing dementia are not well understood. 
Objective: To investigate the effects of positive and negative experiences of social support within key relationships (spouse or partner, children, other immediate family and friends) on the risk of developing dementia in later life. 
Methods: We analysed 10-year follow up data (2003/4 to 2012/13) in a cohort of 10,055 dementia free (at baseline) core participants aged 50 years and over from the English Longitudinal Study of Ageing (ELSA). Incidence of dementia was identified from participant or informant reported physician diagnosed dementia or overall score of informant-completed IQCODE questionnaire. Effects of positive and negative experiences of social support measured at baseline on risk of developing dementia were investigated using proportional hazards regression accommodating interval censoring of time-to-dementia. 
Results: There were 340 (3.4%) incident dementia cases during the follow-up. Positive social support from children significantly reduced the risk of dementia (hazard ratio, HR=0.83, p=0.042, 95% CI: 0.69 to 0.99). Negative support from other immediate family (HR=1.26, p=0.011, CI: 1.05 to 1.50); combined negative scores from spouse and children (HR=1.23, p=0.046, CI: 1.004 to 1.51); spouse, children & other family (HR=1.27, p=0.021, CI=1.04 to 1.56); other family & friends (HR=1.25, p=0.033, CI: 1.02 to 1.55) and the overall negative scores (HR=1.31, p=0.019, CI: 1.05 to 1.64) all were significantly associated with increased risk of dementia.  
Conclusion: Positive social support from children is associated with reduced risk of developing dementia whereas experiences of negative social support from children and other immediate family increase the risk. Further research is needed to better understand the causal mechanisms that drive these associations.