A study from the University of Oxford has reinforced the link between high blood pressure (BP) and an increased risk of developing type 2 diabetes. The authors used records from the UK CPRD (Clinical Practice Research Datalink) to evaluate 4,132,138 people without pre-existing diabetes or cardiovascular disease (median age, 46 years; interquartile range, 26–59 years).
Over a median follow-up of 6.8 years, elevated BP at baseline was associated with a greater incidence of new-onset diabetes. Adjustment for age, gender and BMI attenuated the risk, but the association remained, with very narrow confidence intervals (CIs). Each 20-mmHg increase in systolic BP (SBP) was associated with an adjusted HR of 1.58 (95% CI, 1.56–1.59) for new diabetes, and each 10-mmHg increase in diastolic BP had an HR of 1.52 (95% CI, 1.51–1.54). Interestingly, adjustment for smoking, antihypertensive therapy and lipid-lowering therapy had little effect on the results. The strength of the association declined with age and increasing BMI.
These findings were also confirmed in a meta-analysis of 285,664 people and 17,388 new diagnoses of diabetes. In this, the pooled relative risk of new-onset diabetes per 20-mmHg increase in SBP was 1.77 (95% CI, 1.53–2.05).
The authors take care to point out that it is impossible to infer from these findings whether this association is causal. There is some evidence to support causality from the NAVIGATOR (Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research) trial, in which participants who received valsartan were less likely to develop diabetes compared with placebo (HR, 0.86; 95% CI, 0.80–0.92); however, a meta-analysis has shown that only renin–angiotensin system (RAS) inhibitors have these effects, not other BP-lowering agents. Chronic inflammation, which is associated with obesity, elevated BP and type 2 diabetes, is also reduced by RAS inhibition, and may thus be at the heart of the findings in the current study.
If causality is assumed, these findings suggest that individual and population-based efforts to lower BP may also lower the risk of diabetes, and the authors call for a randomised controlled trial to assess this.
The study can be read in full in the Journal of the American College of Cardiology here.
