We investigated associations between social networks and cognition in a community-based cohort over 10.9 years. While a clear cross-sectional association existed at baseline, there was no evidence that social contact conferred protection against later cognitive decline. If anything, individuals with more frequent contacts and better emotional support at baseline had greater decline, after adjustment. Together, these data suggest that social network changes may be the consequence rather than the cause of cognitive decline, although this conclusion is premature based on these results alone.
One explanation for these findings is that quality of social engagement is more important than quantity. We did not examine the nature and complexity of interactions. Effortful mental activities such as crossword puzzles may prevent cognitive deterioration (Verghese et al. 2003
), perhaps by increasing the number of neocortical synapses and improving neuronal networking (Orrell, Sahakian 1995
), but findings concerning social networks are mixed. This may reflect that one can be surrounded by others but not engaged, particularly for individuals on the cusp of mental decline. For example, one study found that activities requiring creativity and initiative, such as gardening and traveling, reduced the risk of incident dementia within 3 years. Less cognitively demanding activities such as visiting friends and watching television were not protective (Fabrigoule et al. 1995
The longitudinal results contradict earlier findings from the Baltimore ECA that suggested an association between larger network size and better cognition (Holtzman et al. 2004
). This may be because the earlier analysis used data from the first 12 years, while we restricted our sample to respondents who remained in the study for two decades. This subgroup of survivors differed significantly from individuals lost to follow-up. The present analysis also included many younger participants, potentially masking any effect of social networks on cognition. A future study focusing on older persons, who are likely to experience greater cognitive change during the follow-up period than younger individuals, might reveal a longitudinal association between frequency of social contact, emotional support, and cognition.
Our findings concur with other negative studies (Glei et al. 2005
, Seeman et al. 2001
). Previous investigations reporting a positive association had short follow-up (Fratiglioni et al. 2000
) or used cognitive instruments unable to detect mild deficits. Thus, respondents may have been misclassified as cognitively intact when their social withdrawal resulted from emerging mental decline (Bassuk, Glass & Berkman 1999
). We attempted to clarify this issue by using delayed recall, a highly sensitive measure of cognitive dysfunction, and following participants for 10.9 years.
Another possible explanation for our results is the limited variability of social network characteristics in the study population, which reduced the likelihood of detecting an association. Lastly, social networks may primarily affect aspects of cognition that the MMSE and delayed recall task do not assess well, such as executive functioning.
This study has many strengths, including a large, population-based sample, many person-years of follow-up, and the use of two different cognitive assessments, including a sensitive delayed recall task. The major limitation was the use of “survivor” data.
Our results provide no evidence that social network characteristics prevent cognitive decline. Additional longitudinal studies can clarify whether specific aspects of social participation, such as interactive mentally stimulating activities, are beneficial. Conclusive evidence of an association would support the creation of social interventions for aging individuals.
- A longitudinal study shows that social networks do not protect against cognitive and functional decline with aging.
- However, a clear cross-sectional association exists between social network size and cognitive function.
- This suggests that changes in social network characteristics may be the consequence, rather than the cause, of cognitive and functional decline.