Predictors of blood pressure control in patients with diabetes and hypertension seen in primary care clinics

Background: Blood pressure (BP) is not well controlled in the majority of patients with both diabetes and hypertension. This study was designed to identify predictors of BP control in patients with both diabetes and hypertension who are seen in primary care clinics. Methods: This retrospective study was conducted by identifying a cohort of patients diagnosed with diabetes before January 1, 2000 (inception) who met predefined criteria for hypertension at inception and who received primary care in the ensuing 3-year study period (January 1, 2000, to February 31, 2002). Using the mean of all BP values between January 1, 2002, and December 31, 2002, subjects were divided into two groups: those with controlled BP and those with uncontrolled BP. The distribution of clinical predictors was compared between the two groups. Independent predictors were identified using multivariate logistic regression. Results: Predictors of poor BP control were as follows: 1) isolated systolic hypertension at inception (OR= 0.62, CI = 0.47 to 0.82); 2) uncontrolled BP at inception (OR = 0.71, CI = 0.55 to 0.93); 3) use of oral hypoglycemic drugs versus diet and exercise alone or insulin use (OR = 0.73, CI = 0.56 to 0.95); 4) use of three or more antihypertensive drugs (OR = 0.74, CI = 0.56 to 0.97); and 5) older age (OR = 0.98, CI = 0.97 to 0.99). Predictors of better control were 1) use of nitrates (OR = 1.82, CI = 1.26 to 2.64); 2) history of coronary heart disease (OR = 1.47, CI = 1.08 to 2.00); and 3) at least one annual visit to subspecialist physician (OR = 1.43, CI = 1.09 to 1.88). Conclusions: Patients with both diabetes and hypertension who are older, have isolated systolic hypertension, use oral hypoglycemic drugs, or use three or more antihypertensive drugs should be targeted for better BP control. The roles of nitrate medication and subspecialist physicians in achieving better BP control needs further study.