Clinical guidelines recommend maintaining blood pressure levels to below 130/80 mm Hg in high risk patients, including people with diabetes. In a paper published in the British Medical Journal, Eszter Vamos and colleagues from Imperial College London examined the effect of systolic and diastolic blood pressure achieved in the first year of treatment on all cause mortality in patients newly diagnosed with type 2 diabetes, with and without established cardiovascular disease. They carried out a retrospective cohort study using data from the United Kingdom General Practice Research Database on 126 092 adults with a new diagnosis of type 2 diabetes, between 1990 and 2005.
Before diagnosis, 12 379 (9.8%) patients had established cardiovascular disease (myocardial infarction or stroke). During a median follow-up of 3.5 years, they recorded 25 495 (20.2%) deaths. In people with cardiovascular disease, tight control of systolic (less than 130 mm Hg) and diastolic (less than 80 mm Hg) blood pressure was not associated with improved survival, after adjustment for baseline characteristics (age at diagnosis, sex, practice level clustering, deprivation score, body mass index, smoking, HbA1c and cholesterol levels, and blood pressure). Low blood pressure was also associated with an increased risk of all cause mortality. Compared with patients who received usual control of systolic blood pressure (130-139 mm Hg), the hazard ratio of all cause mortality was 2.79 (95% confidence interval 1.74 to 4.48) for systolic blood pressure at 110 mm Hg. Compared with patients who received usual control of diastolic blood pressure (80-84 mm Hg), the hazard ratios were 1.32 (1.02 to 1.78) and 1.89 (1.40 to 2.56) for diastolic blood pressures at 70-74 mm Hg and lower than 70 mm Hg, respectively. Similar associations were found in people without cardiovascular disease. Subgroup analyses of people diagnosed with hypertension and who received treatment for hypertension confirmed initial findings.