Analyses of MIDUS social engagement and cognition data revealed significant positive associations between average reported contacts and support and measures of both executive function and episodic memory, independent of age, education, gender, and race as well as major health conditions and health behaviors. Extending prior work, examination of possible links between reported frequency of negative social exchanges such as excessive criticism and demands or perceptions that others “let you down” and cognition also revealed that greater frequency of such social strain/conflict was significantly and negatively associated with executive function but not episodic memory. Longitudinal social engagement data also revealed that declines in social contacts over the decade between MIDUS I and II were associated with poorer executive function and episodic memory performance.
The wide age range in the MIDUS cohort (35 years and older at the time of the cognitive assessments) also allowed us to test the hypothesis that associations between social engagement and cognition previously documented for older adults would be evident at younger ages as well. Consistent with this hypothesis, we found significant positive associations between social contacts and support and both cognitive outcomes for those younger than the age of 65 years. Social strain/conflict was also significantly associated with poorer executive function and marginally associated with poorer episodic memory in this younger age group. For those older than the age of 65 years, we also found significant positively associations between social contacts and both executive function and episodic memory. For episodic memory, effect sizes for social support and conflict were similar to those seen among the younger age group but were not statistically significant due to larger standard errors. Formal tests for age interactions revealed that associations were significantly stronger among the younger adults for social support and conflict with respect to executive function and stronger for social strain/conflict with respect to episodic memory.
The overall pattern of these findings is consistent with a life course model for social engagement influences on cognition wherein social influences are evident not only at older ages but across the life course. MIDUS data show that among adults aged 32 years and older, those reporting higher average social contacts and social support (based on assessments approximately a decade apart) performed significantly better on tests of executive function and episodic memory, whereas higher average reported frequency of social strain/conflict was associated with significantly poorer performance. Changes over time were also associated with differences in cognitive performance with declines in contact (i.e., reductions in exposure to “positive factors”) associated with poorer performance. Though not statistically significant when accounting for multiple comparisons, there was suggestive evidence that increases in support (i.e., increased exposure to a “positive factor”) were associated with better performance.
Though the MIDUS data provide support for our original hypothesis that social engagement would be associated with better cognition at younger as well as older ages, the fact that a number of the associations were stronger among the younger member of the MIDUS cohort was unexpected. Possible reasons for the stronger associations among those younger than the age of 65 years may include the greater attrition among the older adults from baseline to MIDUS II (when the cognition assessments were made) such that those with the poorest social engagement histories were less likely to remain in the cohort by the MIDUS II follow-up and are thus not included in the current analyses. Had they remained, one might hypothesize that they would have exhibited the poorest cognition and might have contributed to stronger associations between poor social engagement and poor cognition among the older adults. Our pattern of weaker associations at older ages parallels findings for multiple other risk factors (e.g., Berry, Ngo, Samelson, & Kiel, 2010
; Tate, Manfreda, & Cuddy, 1998
) and may, like these others, also reflect in part the greater competing risks at older ages wherein even those with good profiles of social engagement are, for example, more likely than their younger counterparts to have other risk factors that will increase their risks for poorer cognition. Thus, though we controlled for a number of known risk factors for poorer cognition (e.g., health conditions, health behaviors), it is likely that among the older adults, even those with better profiles of social engagement have other age-related physiological or other changes that increase their risks for poorer cognition. Our inability to control more completely for such factors may have reduced our ability to demonstrate the benefits of greater social engagement in the older age groups. Importantly, the current analyses are, to our knowledge, the first to examine patterns of association between social engagement and cognition for those younger than the age of 65 years, so the findings reported here, though intriguing, require further investigation to determine their ultimate import.
Interpretation of the overall findings must also include consideration of several limitations of the MIDUS data. Foremost is the lack of longitudinal cognition data. With only a single assessment of cognition at MIDUS II, analyses presented here provide evidence for “associations” between histories of social engagement and executive function and episodic memory as of MIDUS II. Further investigation of the temporal sequencing of changes in social engagement and changes in cognition must await future longitudinal cognitive data. Such data will allow (as the current data do not) for evaluation of the relative strengths of what are, in all likelihood, reciprocal relationships between social engagement and cognition with cognition and changes in cognition impacting on patterns of social engagement even as social engagement itself influences cognition and trajectories of cognitive aging. The current analyses only allow us to determine the presence of associations between these two important domains without being able to assess the relative strength of the directionality of their respective influences. For the majority of the current MIDUS cohort, however, available cognitive data show performance levels that are sufficiently high that reverse causation—with cognitive function being sufficiently poor as to negatively impact on social engagement—would seem less plausible as the primary explanation for the observed association. Only among the oldest of the MIDUS participants, where cognitive performance is poorest, might one speculate that patterns of social engagement were potentially more affected by cognitive functioning. Whether and how any reciprocal effects come to be manifest over the life course, however, awaits further longitudinal data for both cognition and social engagement. Also, the social engagement data are based on self-reports and thus could be subject to differential response bias (e.g., if those with better cognition are more likely to bias their self-reports toward more positive reporting of social engagement); if so, this could result in an upward bias in estimates of the association between social engagement and cognition. Finally, as noted previously, the MIDUS is a national sample with substantial socioeconomic diversity but is not strictly nationally representative, and the cognitive data were collected only for those remaining in the longitudinal cohort, which, like all longitudinal studies, is positively selected for those who remained healthier and more interested in continuing their participation in the study. Thus, the generalizability of our findings remains to be determined.
These analyses, however, also have a number of significant strengths. First, the age range of the cohort allowed for the first formal tests of the hypothesis that relationships between social engagement and cognition are not restricted to older ages but rather are evident much earlier in life. MIDUS data allowed for testing of these associations among adults as young as 35 years at the time of the cognitive assessments. Second, the MIDUS data provide particularly rich information on social engagement, including assessments of more quantitative aspects such as social contacts as well as more qualitative features, including frequency of both positive social exchanges (social support) and negative exchanges (social strain/conflict). Also, the social engagement data are available at two time points approximately a decade apart, allowing for evaluation of more cumulative aspects of social engagement (i.e., social histories) as they relate to cognition. Third, although the cognitive data are only available at a single time point, the range of measures provides assessments for key cognitive domains known to be important in cognitive aging across the life span. Furthermore, the innovative telephone-based SGST provided enhanced data on speed of processing and executive function through assessments of latencies in task switching.
In summary, MIDUS data provide evidence linking three aspects of social engagement—social contacts, support, and conflict—to both executive function and episodic memory in adults ranging in age from 35 to 84 years. Those reporting greater average contacts and support performed better on both types of cognitive tasks, whereas those reporting greater average frequency of negative social exchanges performed did more poorly. The fact that these associations were evident in younger adults and that changes in these features of social engagement are related to performance points to the potential value of considering more positive aspects of social engagement such as social contacts and support in the context of any future efforts to improve or bolster levels of cognition across the life course. These data also suggest the importance of taking account of risks stemming from higher levels of social strain/conflict. Clearly, further research is needed to confirm these initial findings regarding the associations at younger ages and the impact of negative social exchanges. The current findings, however, will hopefully encourage attention to these questions as we seek to understand how patterns of social engagement impact on cognitive function across the life course and how we might best leverage such knowledge to enhance cognitive development earlier in life and reduce risks for cognitive declines in later life.