Results of a new study found that each 20 mmHg increase in SBP was associated with a 58% higher risk for new onset type 2 DM.
Elevated blood pressure was associated with an increased risk for diabetes, according to an analysis of the electronic health records (EHRs) and a meta-analysis.
The strength of the association declined with increasing body weight and age, but among the overall cohort, each 20 mmHg increase in systolic blood pressure (SBP) was associated with a 58% higher risk for new onset diabetes (hazard ratio 1.58, 95% CI 1.56-1.59), reported Connor Emdin, HBSc, of Oxford University's George Institute for Global Health in England, and colleagues.
The findings support the widely held, but unconfirmed, hypothesis that hypertension is an independent risk factor for type 2 diabetes, they wrote in JACC. They noted that randomized trials are needed to establish causation and to determine whether lowering blood pressure reduces diabetes risk.
"Assuming causality, this analysis suggests that individual- and population-based efforts to lower blood pressure may also lower the incidence of diabetes," they stated.
Diabetes is a major risk factor for stroke, heart attack and other cardiovascular events, with one study showing that patients with type 2 diabetics have a threefold increased risk for cardiovascular disease-related death compared with age- and sex-matched controls without diabetes.
"Elevated BP is associated with chronic inflammation and endothelial dysfunction, both of which appear to be mediators of diabetes risk," Emdin and colleagues wrote. "There is, therefore, a biological rationale to suspect that elevated BP may cause new-onset diabetes."
While many previous cohort studies have explored the proposed association, findings have been mixed. Emdin and colleagues noted that even the largest cohort studies have not been fully powered to investigate the impact of blood pressure on diabetes risk among at-risk subgroups, including overweight or older patients.
The researchers used validated linked EHRs in the U.K. (Clinical Practice Research Datalink) to identify 4.1 million adults without a diagnosis of diabetes or cardiovascular disease (CVD) at baseline.
The primary outcome was a diagnosis of type 2 diabetes or prescription of insulin/antidiabetic drugs.
BP measurements made between January of 1990 and January of 2013 were adjusted for regression-dilution bias by regressing serial BP measurements on a baseline measurement. Hazard ratios for measured BP, adjusted for known risk factors, were multiplied by regression dilution ratios of 2.1 and 2.5 for SBP and diastolic blood pressure (DBP), respectively, to estimate incident diabetes associations with "usual" BP.
Both higher SBP and DBP were associated with an increased risk for new-onset diabetes in the overall cohort. Each 10 mmHg increase in DBP was associated with a 52% increased risk for diabetes (HR 1.52, 95% CI 1.51-1.54).
The subgroup analysis revealed that a 20 mmHg higher SBP was associated with a greater risk for diabetes in those with a body mass index (BMI) of ≤25 kg/m2 (HR 1.89, 95% CI 1.84-1.94) than among those with BMI >35 kg/m2 (HR 1.19, 95% CI 1.16-1.22, P for interaction <.0001).
Also, a 10 mmHg higher usual DBP was associated with a 73% higher risk of diabetes among those with a BMI <20 kg/m2 (HR 1.73, 95% CI 1.68-1.78), compared with a 19% increased risk among those with a BMI >35 kg/m2.
The relative risk of new-onset diabetes per 20mmHg higher usual SBP declined with increasing age, from an HR of 2.00 (95% CI 1.96 to 2.04) at age 30 to 50 to an HR of 1.14 (95% CI 1.11 to 1.17) at age 71 to 90.
The researchers conducted a meta-analysis of 30 prospective observational studies, with a total of 285,664 participants and 17,388 incident diabetes events.
"The overall pooled coefficient, including our and previous cohort studies, was 76% per 20 mmHg higher usual SBP (RR 1.76, 95% CI 1.56-1.97), they wrote. "Estimates were similar when 5 studies that used a normal approximation to determine the BP difference associated with the provided relative risk were excluded."
In an accompanying editorial, Donna Arnett, PhD, MSPH, of the University of Alabama at Birmingham called the study an "exceptionally rigorous" evaluation of the relationship between blood pressure and incident diabetes.
But she added that while the findings may bolster the hypothesis that higher blood pressure has a causal relationship with diabetes, "they are unlikely to motivate any changes in clinical practice."
"This study provides a strong rationale for continued research into the biological basis and pharmacological implications of the observed association," she concluded.
ACTION POINTS
The research was funded by the U.K. National Institute for Health Research.
Emdin disclosed support from the Rhodes Trust.
Emdin and most co-authors disclosed no relevant relationships with industry. Some co-authors disclosed relevant relationships with the National Institute of Health Research, the Australian Health and Medical Research Council, Amgen, Novartis, and the National Institute of Health Research Oxford Biomedical Research Centre.
Arnett disclosed no relevant relationships with industry.
Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner
Primary Source: Journal of the American College of Cardiology
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