The associations of social relationships with risk of incident mild cognitive impairment in older adults.

Abstract

Introduction: Discovering effective preventive options for dementia at earlier stages of the disease pathogenesis, such as mild cognitive impairment (MCI), is an increasingly important public health matter. Social relationships may act to prevent cognitive impairment by providing mental stimulation as well as positively influencing health behaviors and psychological processes. The objective of this study was to investigate the role of social relationships on risk of MCI in older adults. Methods: We used data from the National Alzheimer's Coordinating Center, which maintains a set of standardized clinical data from participants that were evaluated by one of 33 National Institute on Aging funded Alzheimer's Disease Centers located across the U.S. Subjects were cognitively normal at baseline, aged 55 and older, and followed prospectively for up to 7 years for incident MCI. Social relationships, our primary exposure, included marital status (i.e., married, divorced/separated, widowed, or never married), living situation (i.e., living with spouse/partner, living with others, living alone), having children (yes, no), and having siblings (yes, no). Cox proportional regression models evaluated the association between risk of MCI and baseline social relationships, separately, with adjustment for confounding exposures (demographics) in primary models and further adjustment for distal factors (health behaviors, e.g., smoking, alcohol abuse, substance abuse) and proximal factors (health conditions, e.g., cardiovascular disease, metabolic conditions, depression, psychiatric disorder, neurological conditions) at baseline in secondary models. Results: The analytic sample included 4,917 subjects, followed, on average, for 3.2 years (SD=1.5), 763 of whom were diagnosed with MCI. In unadjusted analysis, MCI was associated with marital status (p<0.001) and living situation (p<0.001), but not with having children (p=0.93) or having siblings (p=0.38). However, in multivariable analyses none of the social relationships were independently associated with risk of MCI after adjusting for demographic characteristics (all p>0.05). Conclusions: In contrast to previous studies, social relationships were not associated with risk of MCI after iterative adjustment for demographics, as well as health behaviors and health conditions in this analysis. Differences in results may have been due to lack of variability in exposure measures, a high rate of censoring, and/or differential drop-out across outcome status. Differences may also be due to strict entry criteria that may have better addressed the possibility of reverse causation than previous studies. Future studies that include sensitive methods and measures are needed to further investigate the potential link between social relationships and cognition. Other modifiable factors may be more strongly associated with risk of MCI and should also be investigated as possible levers for the prevention of dementia.