BackgroundBy the lengthening of life span, the incidence of chronic diseases such as hypertension and uncontrolled hypertension has increased. This study aims to determine the prevalence of uncontrolled hypertension and its related factors in the age group of 50–74 years in Shahroud, northeast Iran.MethodsThe data of the third phase of the Shahroud Eye Cohort Study were used in this study. This phase of the cohort study included 4394 participants aged 50 to 74 years from the previous phases. In addition to ophthalmological and optometric examinations, demographic characteristics, blood biochemistry tests, and blood pressure measurements were performed in this phase. Individuals with a blood pressure ≥ 140/90 mm/Hg (being treated or not treated with antihypertensive medicines) were defined as uncontrolled hypertension. In patients with diabetes and chronic kidney disease, blood pressure equal to or higher than 130/80 mm/Hg was considered uncontrolled hypertension. Descriptive statistics and multiple logistic regression were used to analyze the data.FindingsOverall, the prevalence of uncontrolled hypertension out of all the participants was 61.7% (95% CI: 60.3–63.2). Multiple regression results showed that the male gender (OR: 2.1, 95% CI: 1.5–2.9), patients with diabetes (OR:3.2, 95% CI: 2.4–4.3), and patients with chronic kidney disease (CKD) (OR: 3.2, 95% CI: 2.5–4.1) increased the risk of uncontrolled hypertension while in patients with cardiovascular disease (OR: 0.6, 95% CI: 0.4–0.8) and polypharmacy (OR: 0.2, 95% CI: 0.1–0.2) reduced the risk of uncontrolled hypertension.ConclusionThe present study showed that uncontrolled hypertension has a high prevalence, and factors such as male gender, diabetes, and CKD are associated with this disorder. So, it is recommended to take the necessary measures to formulate and implement immediate actions to prevent or control hypertension.