Survival Time to Development of Hypertension and Its Predictors among a Cohort of Diabetic Patients in Health Facilities of Gurage Zone: A Retrospective Follow-Up Study

Abstract

Background: It is expected that around 50% of individuals with diabetes mellitus will develop hypertension in the course of medical follow-up. However, with strict medical follow-up and adherence to medical advice the incidence of hypertension can be highly reduced and the time to occurrence can be delayed. Therefore, this paper aimed to measure the time to development of hypertension and identify its predictors among a 10-year cohort of diabetic patients who have medical follow-up in health facilities of Gurage Zone.

Methods: An institution-based retrospective cohort study was conducted in diabetic follow-up clinics of Gurage Zone by reviewing 540 consecutively selected records among the records enrolled from January 1, 2010 to December 31, 2019. The outcome variable was incidence rate and survival time to the occurrences of hypertension (a systolic blood pressure at or above 140 mmHg and/or a diastolic blood pressure at or above 90 mm Hg and known hypertensive cases taken from adults' age ≥18 years) among admitted diabetic patients (fasting blood sugar ≥126 mg/dL or random blood sugar ≥200 mg/dL). Data were collected using a standardized checklist by trained professionals by reviewing records of all clients ever enrolled. Data were cleaned and entered by Epi info version 7 and analyzed by STATA. A Cox-proportional hazard regression model was built to identify predictors of development of hypertension.

Results: A total of 540 clients were followed for different periods with a median follow-up period of 2.3 years which gives 3,200 person-years of observation. Two hundred and seventy-six (51.1%) participants were males and the mean age of was 52.2 (+11.7) years. Three hundred (55.6%) participants were urban dwellers. The overall incidence density rate (IDR) of hypertension in the cohort was 48.6 cases per 1,000 persons-year. Older ages adjusted hazard ratio (AHR)=4.0 (95% CI=2.26-7.82), body mass index (BMI) >25 kg/m² AHR=2.3 (95% CI=1.06-3.68), Type II diabetes mellitus (DM) AHR=2.0 (95% CI=1.16-3.04), presence of comorbidity AHR=2.9 (95% CI=1.74-4.58), and poor drug adherence AHR=2.5 (95% CI=1.45-4.65) predicted the development of hypertension.

Conclusion: The risk of occurrences of hypertension among diabetic patients was high at the early periods and the risk was less at the late diabetic periods and the incidence density rate of hypertension among diabetic patients was high. In addition, age, BMI, type of DM, comorbidity, and drug adherence were independent predictors of occurrences of hypertension. Therefore, intervention to further reduce its occurrence has to focus on drug adherence and prevention of infection.

Keywords: diabetes mellitus; hypertension; incidence; survival.