Low blood pressure increases diabetes mortality risk

Sep 3 2012

By Liam Davenport, medwireNews Reporter

Tight blood pressure control fails to confer a survival benefit in patients newly diagnosed with Type 2 diabetes, and may even increase mortality risk when low blood pressure levels are achieved, UK investigators have discovered.

Writing in the British Medical Journal, the team says: "Although no causality can be implied for these relations, our results suggest that 'the lower the better' approach might not apply to blood pressure control beyond a critical level in high risk patients.

"Since there is currently no robust evidence available for lowering the blood pressure below 130/80 mmHg in people with diabetes, it might be advisable to maintain blood pressure between 130-139/80-85 mmHg, supported by other therapeutic and lifestyle interventions to improve cardiovascular outcomes in patients with diabetes."

Examining data on 126,092 adults from the United Kingdom General Practice Research Database who were diagnosed with Type 2 diabetes between 1990 and 2005, Matthew Harris, from Imperial College London, and colleagues found that 9.8% had a prior diagnosis of cardiovascular disease.

Over a median follow-up period of 3.5 years, 25,495 (20.2%) patients died, at an event rate of 48.3 per 1000 patient years. Mortality was 28.6% in patients with cardiovascular disease and 19.3% in those without.

Cox proportional hazards model analysis, controlling for age at diagnosis, gender, practice level clustering, deprivation score, body mass index, smoking, glycated hemoglobin, cholesterol levels, and blood pressure, revealed that tight blood pressure control, defined as systolic blood pressure (SBP) below 130 mmHg and diastolic blood pressure (DBP) below 80 mmHg, did not lower the risk for all-cause mortality, except in patients without cardiovascular disease who had DBP levels of 75-79 mmHg, in whom a small 13% reduction in relative risk was observed.

Moreover, at lower SBP and DBP levels the all-cause mortality risk was actually increased.

Specifically, the team found that in patients with cardiovascular disease, the hazard ratio for all-cause mortality was 2.79 for SBP lower than 110 mmHg, 1.32 for DBP 70-74 mmHg, and 1.89 for DBP less than 70 mmHg relative to usual control levels (130-139 for mmHg SBP and 80-84 mmHg for DBP).

For those without cardiovascular disease, the hazard ratio for all-cause mortality was 1.58 for SBP 110-119 mmHg, 2.42 for SBP lower than 110 mmHg, 1.17 for DBP 70-74 mmHg, and 1.54 for DBP lower than 70 mmHg.

Interestingly, the results indicate that uncontrolled SBP and DBP were not significantly associated with increased mortality on multivariate analysis, regardless of the presence of cardiovascular disease.

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