Outpatient versus telephone follow-up and blood pressure control in China: a longitudinal study in primary care

As the population ages, long-term standardized management of hypertension has become a critical task for primary healthcare systems. Telephone follow-up is widely used as a supplementary approach to outpatient care; however, its long-term effectiveness in real-world settings remains unclear. This study aimed to compare outpatient and telephone follow-up in relation to blood pressure control among older patients with hypertension and to examine whether differences in follow-up interval and visit frequency may help explain these associations. A longitudinal cohort was constructed using electronic health record data from 2013 to 2024, including patients with hypertension who had at least two follow-up visits. Follow-up modality was treated as a time-varying exposure, with the modality recorded at each visit used to predict blood pressure outcomes at the subsequent visit. Multiple imputation was used to address missing baseline covariates. Stabilized inverse probability of treatment weights were then applied to estimate marginal structural models accounting for time-varying confounding. Weighted logistic regression was used to estimate the association between follow-up modality and blood pressure control, while weighted linear models were used to assess changes in systolic and diastolic blood pressure. A composite “good management” indicator was further examined as a potential pathway linking follow-up modality to blood pressure control. Telephone follow-up was associated with lower odds of achieving blood pressure control compared with outpatient follow-up (odds ratio = 0.836, p < 0.05). After further adjustment for the “good management” indicator, the association was attenuated (odds ratio = 0.863, p < 0.05). Telephone follow-up was also associated with a lower likelihood of achieving good management (odds ratio = 0.500, p < 0.001). For continuous outcomes, telephone follow-up was associated with an increase in systolic blood pressure of 0.769 mmHg and a decrease in diastolic blood pressure of 0.714 mmHg per follow-up interval (both p < 0.001). In real-world primary care settings, outpatient follow-up was associated with better long-term blood pressure control than telephone follow-up among older patients with hypertension. Differences in follow-up intensity may partly explain this association. Not applicable.