JMIR Publications

ABSTRACT

Background:

Although the association between social isolation and risks of subsequent cardiovascular disease (CVD) is well documented, most studies assess social isolation at only one timepoint, and few consider the association using repeatedly measured social isolation.

Objective:

To examine the associations of social isolation trajectories with incident CVD in a large cohort of middle-aged and older adults.

Methods:

This study used the four waves (wave 1, wave 2, wave 3, wave 4) data of the China Health and Retirement Longitudinal Study (CHARLS). We defined June 2011 to September 2015 as our exposure period (from wave 1 to wave 3), and September 2015 to March 2019 (wave 4) as our follow-up period. Based on inclusion and exclusion criteria, our final analytic sample included 8422 individuals who had no CVD in CHARLS in waves 1-3 and were fully followed up in wave 4. Social isolation was ascertained using a validated questionnaire at 3 consecutive, biennial timepoints from wave 1 to wave 3, and individuals were assigned to 3 predefined social isolation trajectories based on their scores at each wave (consistently low, fluctuating, and consistently high). Incident CVD included self-reported physician-diagnosed heart disease and stroke combined. Cox proportional hazard models estimated the associations of social isolation trajectories with risks of incident CVD, adjusting for demographics, health behaviors, and health conditions.

Results:

Of the 8422 participants (mean [SD] age at baseline, 59.76 (10.33) years), 4219 (50.1%) were males. The majority (62.5%) had consistently low social isolation over time, and 16.6% had consistently high social isolation over the exposure period. During the 4 years of follow-up, 746 incident CVDs occurred (heart disease, 450 cases; stroke, 336 cases). Compared with individuals with consistently low social isolation, those with fluctuating social isolation (adjusted HR, 1.27 [95% CI, 1.01-1.59]) and consistently high social isolation (adjusted HR, 1.45 [95% CI, 1.13-1.85]) had higher risks for incident CVD after adjusting for demographics (i.e., age, sex, residence, and educational level), health behaviors (i.e., smoking status, and drinking status), and health conditions (i.e., body mass index; history of diabetes, hypertension, dyslipidemia, chronic kidney disease; use diabetes medications, hypertension medications, lipid-lowering therapy; and depressive symptoms scores).

Conclusions:

In this cohort study, middle-aged and older adults with fluctuating and consistently high social isolation exposure had higher risks of the onset of CVD than those without exposure. The findings suggest that routine screening for social isolation and efforts to improve social connectedness merit increased attention for preventing CVD among middle-aged and older adults.