Impact of subjective cognitive decline on frailty in elderly patients with metabolic syndrome: the parallel mediating effects of physical activity and depression

Elderly patients with metabolic syndrome often present with concurrent subjective cognitive decline and frailty, yet the underlying mechanisms linking these conditions remain unclear. This study aims to explore the parallel mediating effects of physical activity levels and depression on the relationship between subjective cognitive decline and frailty in elderly patients with metabolic syndrome, identify potential pathways and key factors through which subjective cognitive decline influences frailty, and provide evidence to support the development of intervention strategies.

A cross-sectional study was conducted on 348 hospitalized elderly patients with metabolic syndrome admitted to 10 internal medicine departments (including Respiratory Medicine, Neurology, Hypertension and Endocrinology, and Cardiology) in Daping Hospital of Army Medical University from June to December 2024. Subjective cognitive decline was assessed using the Subjective Cognitive Decline Questionnaire (SCD-Q9), depression using the Center for Epidemiologic Studies Depression Scale 10 (CES-D 10), frailty using the Fatigue, Resistance, Ambulation, Illnesses, and Loss of Weight (FRAIL) Scale, and physical activity levels using the International Physical Activity Questionnaire Short Form (IPAQ-SF). Pearson correlation analysis was performed to assess the correlation coefficients between frailty, subjective cognitive decline, depression, and physical activity levels. The Process macro in SPSS 27. 0 was used to construct the mediation effect model.

Subjective cognitive decline was positively correlated with depression (r=0. 210, P<0. 001) and frailty (r=0. 275, P<0. 001), and negatively correlated with physical activity levels (r=-0. 199, P<0. 001). Physical activity levels were negatively correlated with frailty (r=-0. 228, P<0. 001), and frailty was positively correlated with depression (r=0. 251, P<0. 001). Physical activity levels and depression exerted parallel mediating effects between subjective cognitive decline and frailty, with effect values of 0. 009 (95%CI: 0. 003 to 0. 017) and 0. 012 (95%CI: 0. 004 to 0. 021), accounting for 12. 50% and 16. 67% of the total effect, respectively.

Physical activity levels and depression play parallel mediating roles between subjective cognitive decline and frailty in elderly patients with metabolic syndrome. Clinicians should emphasize screening for subjective cognitive decline in these patients. And interventions aimed at enhancing physical activity and targeting depressive symptoms may help delay frailty progression and improve quality of life.