Interactive effect of social isolation and poor nutritional status on cognitive function decline in older adults

Social isolation and poor nutritional status are well-established independent risk factors for cognitive decline. However, few studies have examined their combined effects on cognitive decline. This cross-sectional study evaluated the synergistic association between social isolation, poor nutritional status, and cognitive decline in older adults aged 60 years and above.

Data from 10,501 older Chinese adults were analyzed. Univariate and multivariate logistic regression analyses were conducted to determine the relationship between social isolation, poor nutritional status, and cognitive decline. Interaction effects were evaluated using the relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), and synergy index (S).

The prevalence of cognitive decline in older adults was 12.87%. Multivariate analysis revealed odds ratios for cognitive decline associated with social isolation and poor nutritional status of 1.580 [95% confidence interval (CI): 1.379-1.811] and 3.667 (95% CI: 3.200-4.203), respectively. A significant synergistic interaction effect between social isolation and poor nutritional status on cognitive decline was observed (RERI = 2.199, AP = 0.362, S = 1.765), and this effect persisted across sex and age subgroups.

Among older Chinese adults, social isolation and poor nutritional status exert a significant synergistic association with cognitive decline. These findings highlight the importance of integrated interventions targeting both social isolation and nutritional status to support cognitive health in older populations.