This study aimed to identify the dual trajectories of social isolation and depression among middle-aged and older patients with hypertension, discuss the relationship between the dual trajectories, and investigate common influential factors. Method Using data from 2013 to 2020 of the China Health and Retirement Longitudinal Study (CHARLS), a longitudinal cohort was formed for the study. A group-based trajectory model was used to identify trajectories of social isolation and depression in 3 223 middle-aged and older patients with hypertension and the relationship between the dual trajectories. Multi-class logistic regression was used to analyze common influential factors of the dual trajectories.

Three trajectories of social isolation were identified: low-stable without social isolation, medium-stable without social isolation, and high-increasing with social isolation. Three depression trajectories were observed: low-stable without depression, medium-increasing with depression, and high-stable with depression. Dual-trajectory analysis showed in middle-aged and older patients with hypertension who were in the medium-stable without social isolation and high-increasing with social isolation trajectory groups, the probability of depression trajectories in the medium-increasing with depression and high-stable with depression groups was 61.84% to 87.46%. In middle-aged and older patients with hypertension who belonged to the medium-increasing with depression and high-stable with depression trajectory groups, the probability of social isolation in the medium-stable without social isolation and high-increasing with social isolation trajectory groups was 70.03% to 91.63%. The level of education(social isolation trajectories in middle school RRR=0.756, 95% CI：0.599-0.954, RRR=0.496, 95% CI: 0.326-0.755; social isolation trajectories in high school or above RRR=0.516, 95% CI: 0.375-0.709, RRR=0.262, 95% CI: 0.137-0.501; depression trajectories in middle school RRR=0.773, 95% CI: 0.622-0.959, RRR=0.728, 95% CI: 0.574-0.994, depression trajectories in high school or above RRR=0.421, 95% CI: 0.309-0.571, RRR=0.439, 95% CI: 0.253-0.763) and sleeping 7-9 hours a night (social isolation trajectories RRR=0.824, 95% CI: 0.681-0.997, RRR=0.596, 95% CI: 0.440-0.806; depression trajectories RRR=0.597, 95% CI: 0.501-0.711, RRR=0.486, 95% CI: 0.362-0.653) were common influential factors of the dual trajectories of social isolation and depression.

There is a high degree of consistency and significant correlation between the social isolation trajectory and the depression trajectory. Interventions targeting the dual trajectories and co-factors of social isolation and depression should be considered to improve their effectiveness.