Joint Modeling of Longitudinal Systolic and Diastolic Blood Pressure Measurements of Hypertensive Patients Receiving Treatment

Hypertension is a chronic disease that has a major health problem over the centuries due to its significant contribution to the global health burden. It is also called high blood pressure, described by two measured quantities, Systolic blood pressure (SBP) and diastolic blood pressure (DBP). Hence, joint longitudinal model was used to address how the evolution of SBP is associated with the evolution of DBP. The objective was to investigate the joint evolution and association of SBP and DBP measurements of hypertensive patients and identify the potential risk factors affecting the two end points. In this this study 354 hypertensive patients with age greater than or equal to 18 years, who were on treatment, and who had measured at least three times were included. For a close examination of the separate and joint models, first, each of the outcome was analyzed separately using the linear mixed model. Then, a joint model was considered to study the joint evolution and identify the potential risk factors affecting the two responses. The joint model results in model improvement in fit, and hence the preferred one, based on AIC criteria. Based on the joint model, sex, baseline age, and place of residence were the significant factors for the progression of blood pressure, while family history and all the interaction term except age by time did not appear significant. The result from the joint model suggested a strong association between the evolutions and a slowly increasing evolution of the association between SBP and DBP.