Association of smartphone ownership with health literacy, lifestyle behaviors, and cardiovascular outcomes among cardiology outpatients

Background Smartphones are increasingly used to access health information and to support personal health management, potentially influencing health behaviors and self-care. However, disparities in digital access ("digital divide") may influence health literacy and clinical outcomes, particularly in older patients with cardiovascular disease. This study aimed to investigate whether smartphone ownership, as a marker of digital access, is associated with health literacy, lifestyle behaviors, and major clinical outcomes among cardiology outpatients. Methods From August 2022 to March 2023, 1,034 cardiology outpatients completed a questionnaire survey (median age, 74 years; 37% female) and were enrolled in the study. The survey assessed smartphone ownership, lifestyle behaviors, and health literacy using the Communicative and Critical Health Literacy (CCHL) scale. The primary outcome was a composite cardiovascular event, defined as cardiovascular death, worsening heart failure (requiring hospitalization or urgent outpatient visit with intravenous therapy), non-fatal myocardial infarction, or non-fatal stroke. The associations between smartphone ownership and these outcomes were examined. Results Overall, 68% of the participants reported owning a smartphone. Smartphone owners were significantly younger than non-smartphone owners (median age 71 [65–77] vs. 80 [74–85] years; p < 0.001). They also had higher CCHL scores and more frequent internet use. Several lifestyle indicators, including bathing frequency and pet ownership, were more common among smartphone owners, whereas regular exercise showed a non-significant trend (p = 0.096) (Figure 1). Although left ventricular ejection fraction did not differ significantly between groups (62% [56–66] in non-owners vs. 62% [57–66] in smartphone owners; p = 0.924), smartphone owners had lower B-type natriuretic peptide (BNP) levels (44 [21–94] vs. 27 [12–59] pg/mL; p < 0.001), higher estimated glomerular filtration rates (eGFR) (53 [41–64] vs. 59 [49–69] mL/min/1.73 m²; p < 0.001), and lower Clinical Frailty Scale scores (2 [2–3] vs. 2 [2–2]; p < 0.001). Over a median follow-up of 371 days, 48 patients (5%) experienced composite cardiovascular events, which occurred significantly less among smartphone owners (log-rank p < 0.001) (Figure 2). This association remained significant even after adjusting for age, sex, Clinical Frailty Scale score, and BNP level (adjusted hazard ratio, 0.49, 95% confidence interval: 0.26–0.93; p = 0.028). Conclusion Among cardiology outpatients, smartphone ownership was associated with higher health literacy, healthier lifestyle characteristics, and a lower risk of cardiovascular events. These findings highlight the clinical relevance of digital access, suggesting that addressing the digital divide may be an important component of digital health strategies to support self-care and risk reduction in patients with cardiovascular disease.