Blood pressure and complications in individuals with type 2 diabetes and no previous cardiovascular disease: national population based cohort study

OBJECTIVES To compare the risk associated with systolic blood pressure that meets current recommendations (that is, below 140 mm Hg) with the risk associated with lower levels in patients who have type 2 diabetes and no previous cardiovascular disease. DESIGN Population based cohort study with nationwide clinical registries, 2006-12. The mean follow-up was 5.0 years. SETTING 861 Swedish primary care units and hospital outpatient clinics. PARTICIPANTS 187 106 patients registered in the Swedish national diabetes register who had had type 2 diabetes for at least a year, age 75 or younger, and with no previous cardiovascular or other major disease. MAIN OUTCOME MEASURES Clinical events were obtained from the hospital discharge and death registers with respect to acute myocardial infarction, stroke, a composite of acute myocardial infarction and stroke (cardiovascular disease), coronary heart disease, heart failure, and total mortality. Hazard ratios were estimated for different levels of baseline systolic blood pressure with clinical characteristics and drug prescription data as covariates. RESULTS The group with the lowest systolic blood pressure (110-119 mm Hg) had a significantly lower risk of non-fatal acute myocardial infarction (adjusted hazard ratio 0.76, 95% confidence interval 0.64 to 0.91; P=0.003), total acute myocardial infarction (0.85, 0.72 to 0.99; P=0.04), non-fatal cardiovascular disease (0.82, 0.72 to 0.93; P=0.002), total cardiovascular disease (0.88, 0.79 to 0.99; P=0.04), and non-fatal coronary heart disease (0.88, 0.78 to 0.99; P=0.03) compared with the reference group (130-139 mm Hg). There was no indication of a J shaped relation between systolic blood pressure and the endpoints, with the exception of heart failure and total mortality. CONCLUSIONS Lower systolic blood pressure than currently recommended is associated with significantly lower risk of cardiovascular events in patients with type 2 diabetes. The association between low blood pressure and increased mortality could be due to concomitant disease rather than antihypertensive treatment.